European Review for Medical and Pharmacological Sciences 2021; 25: 4579-4596 nucleatum and alteration of the oral microbiome: from pregnancy to SARS-COV-2 infection

A. DESSÌ1, A. BOSCO2, R. PINTUS1, G. ORRÙ3, V. FANOS1

1Neonatal Intensive Care Unit, University Hospital of Cagliari, Monserrato, Cagliari, Italy 2Medical Lab, Sports Medicine and Physiotherapy Center, Vinovo, Turin, Italy 3Department of Surgical Sciences, Molecular Biology Service (MBS), University of Cagliari, Cagliari, Italy

Angelica Dessì and Alice Bosco contributed equally to this work

Abstract. – OBJECTIVE: The human being Key Words: has evolved in close symbiosis with its own eco- , Sars-Cov-2 infection, logical community of commensal, symbiotic and Microbiome, Oral dysbiosis. pathogenic . After the intestinal micro- biome, that of the oral cavity is the largest and most diversified. Its importance is reflected not only in local and systemic diseases, but also in Introduction pregnancy since it would seem to influence the . The human beings are inseparable from their MATERIALS AND METHODS: This is a liter- own microbial community, with whom they have ature review of articles published in PubMed evolved over millions of years, establishing a about Fusobacterium Nucleatum and both its implications with systemic and oral health, ad- perfect symbiotic relationship, essential for main- verse pregnancy outcomes, flavors perception taining a good state of health. Indeed, together and its interference in the oral-nasal mucosal they form a real super-organism, where this sym- immunity. biosis is maintained thanks to a dynamic balance. RESULTS: It is in maintaining the microbi- This cooperation brings various benefits to the ome’s homeostasis that the Fusobacterium nu- host organism. It confers resistance to coloniza- cleatum, an opportunistic tion by pathogens, supporting both the defensive of the oral cavity, plays a crucial role both as a systems and the antioxidant activity. Moreover, it bridge microorganism of the tongue biofilm, and in maintaining the balance between the differ- favors the correct functionality of the cardiovas- ent species in the oral-nasal mucosal immuni- cular and digestive systems, without forgetting ty also by taste receptors interaction. It is also the important contribution to numerous metabol- involved in the flavor perception and its detec- ic processes1. tion in the oral microbiome of children from the This microbial community was called microbi- first days of life suggests a possible physiolog- ome by Nobel laureate Joshua Lederberg with the ical role. However, the dysbiosis can determine intention of defining a real ecological community its pathogenicity with local and systemic conse- of commensal, symbiotics and pathogenic bacte- quences, including the pathogenesis of respira- tory infections. ria that literally share the body space with the hu- CONCLUSIONS: It is interesting to evaluate man being. Futhermore, nowdays, it is also known its possible correlation with Sars-CoV-2 and that the various microorganisms, the microbiota, the consequences on the microflora of the oral which make up the microbiome are not individual cavity, both to promote a possible broad-spec- single-cell organisms present in free form, but trum preventive action, in favor of all subjects they aggregate in an organized structure firmly for whom, by promoting the eubiosis of the oral attached to the surfaces. This structure is the microbiome, a defensive action could be envis- aged by the commensals themselves but, above biofilm, inside which there is both a close cooper- all, for patients with specific comorbidities and ation and a healthy antagonism between different therefore already prone to oral dysbiosis. species. Within the biofilm there is also a fruitful

Corresponding Author: Angelica Dessì, MD; e-mail: [email protected] 4579 A. Dessì, A. Bosco, R. Pintus, G. Orrù, V. Fanos communication between the various components ria, , , Chloroflexi, Fir- through quorum-sensing. The presence of the micutes, , Gracilibacteria (GN02), microbiome is essential for the human organism , , SR1, Synergistetes, in the same way as the set of cells that compose and Saccharibacteria (TM7)5. it. In fact, it is now known how numerous factors The colonization by such a large number of can influence this precious ecosystem which must species is also favored by other factors such as therefore be protected and considered as a whole an optimal temperature (about 37°C), adequate with the host organism2. Pregnancy, as well as hydration (saliva and crevicular fluid), a favor- numerous systemic pathologies, is in fact closely able pH (about 6.5-7) and a richness of nutrients related to the health of the oral microbiome as its including proteins present in saliva, glycoproteins alteration can cause adverse effects. Similarly, and the crevicular fluid. The maintenance of ho- respiratory tract infections seem to be associated meostasis despite the presence of a high microbial with oral health. Thus, it is questionable whether, load, is normally guaranteed by the close collab- in the midst of the Covid-19 pandemic, the pre- oration between the host’s immune system and vention of oral dysbiosis can offer any advantag- the set of resident microorganisms. Indeed, there es. These hypotheses emerge from the analysis is the pro and anti-inflammatory activity of the of the literature concerning the Fusobacterium various bacterial species and the presence in the nucleatum, an opportunistic bacterium of the oral saliva and in the crevicular fluid of both nutrients cavity, a pathogen, essential in the creation of the for the microbiota itself and of molecules with biofilm at the level of the buccal cavity, tongue antimicrobial action including type A immuno- and subgingival plaque3. It plays a key role in globulins, lactoferrin and nitrates1. the onset of periodontal pathology and is related Furthermore, both the cells of the epithelial both to various systemic pathologies and to some mucosa of the oral cavity and those of the im- adverse effects in pregnancy. Therefore, it may mune system act directly and indirectly in main- be interesting to evaluate its presence both during taining the balance within the microbiome6. In gestation, a non-pathological clinical condition fact, there is a close collaboration: the mucosal associated with an alteration of the microbiome, cells express a series of antimicrobial peptides, and in children from birth in order to investi- such as ß-defensins, also capable of stimulating gate its possible function. Moreover, the same APCs7, meaning the Antigen Presenting Cells. alteration of the microbiome can be decisive in These cells, in turn, activate the specific immune infectious diseases of the respiratory tract, such response. The mucosal cells also express chemo- as Sars-Cov-2, both at the pathogenetic level and kines, necessary for the recruitment of mono- as a possible complication. A further correlation cytes and neutrophils, and cytokines, which are between the two microorganisms to be analyzed, also essential for the specific immune response8. is associated with the possible repercussions on In the study by Krisanaprakornkit et al9 it has the olfactory system. been shown that the production of these mole- cules by the cells of the gingival epithelial mu- Oral Microbiome Before and cosa occurs both in response to an inflammatory After Pregnancy stimulus and thanks to the continuous stimulation After the intestinal microbiome, that of the operated by the microbiota. Indeed, purely peri- oral cavity is the largest and most diverse in the odontopathogenic microorganisms such as Por- human body. It hosts more than 700 species of phyronomas (P. gingivalis) do not show the afore- microorganisms that find an excellent habitat in- mentioned properties, as the attempt to escape the side the mouth where they can colonize different human immune system is one of the determining surfaces including teeth, , the gingival sul- factors of virulence. In fact, elevated numbers of cus, the palate and the lips4. Among these loca- certain oral bacteria, especially P. gingivalis, has tions, the teeth represent a very particular area as, been correlated with higher incidence of major unlike the mucous membranes, they do not fall fatals diseases like pancreatic cancer and liver apart and can therefore represent a perfect district cirrhosis 10. With regard to this, in recent years, for a firm bacterial adhesion. It is precisely this the correlation between oral microbiota and sys- heterogeneity of surfaces within the oral cavity temic diseases has been studied in greater depth. that justifies a well-varied microbiome. In fact, Even if further investigation is needed11, with the very different microbial species can be found, contribution of new analytical techniques like, for belonging to as many as 12 phyla: Actinobacte- example metagenomics and culturomics, is now

4580 Fusobacterium nucleatum and alteration of the oral microbiome possible to identify a large number of bacterial ilus, Neisseria, Rothia and Streptococcus found species that was hardly detectable before12-14. by various studies in non-pregnant women24,25. This complex balance between the immune sys- The above studies indicates the results of similar tem and the microbiome is fundamental for the investigations carried out previously26. Similarly, well-being of every humans. While its alteration, an increase in pathogenic taxa has also been the so-called dysbiosis, can determine systemic and observed at level of species in pregnant women, local pathological situations. It can cause mainly especially of Prevotella species, Porphyromonas periodontal pathology, meaning a chronic inflam- gingivalis and Fusobacterium nucleatum21. How- mation of the , gum, periodontal liga- ever, if the abundance of periodontal-pathogenic ment and alveolar bone15,16. The importance of this species is associated with the high frequency of balance is demonstrated by the fact that a possible during pregnancy21, the species most therapeutic intervention is the total removal of the closely associated with gingival bleeding were resident altered flora rather than the insertion of poorly represented. This could be explained by specific predatory bacteria of pathogenic species17. the fact that, given the polymicrobial nature of Indeed, the composition of a healthy oral mi- periodontal pathologies and the high complexity crobiota is quite stable after its complete mat- of the microbiome also due to the identification uration in childhood, albeit with numerous in- of new species, as confirmed by Patini et al27, it is ter-individual variables. Nevertheless, there are not only the most present species that determine several factors that can perturb its composition, the balance of the ecosystem but the complex of including the important variation of the hormon- interactions between the various components28,29. al structure that occurs during pregnancy, some In addition to this, it would seem that for metabolic disease such as diabetes mellitus, the the progression from gingivitis, an initial and use of antibiotics, stress, diet, smoking, oral hy- reversible inflammatory state of the soft tis- giene, the different composition of saliva and par- sues surrounding the tooth, to a significant ticular genetic characteristics of each individual. pathological stage such as periodontitis, certain During pregnancy, a woman’s high hormone environmental factors are also decisive, includ- levels can cause important changes that can lead ing diet and poor oral hygiene. Indeed, it is to an immune-compromised state18. This could common for women to change their diet during be responsible for both the higher susceptibility pregnancy, especially initially, with a strong to infections and for an alteration of the oral carbohydrates’ imbalance and that, given the microbiota, with a subsequent higher gum in- gingival sensitivity and possible nausea, oral flammability and bleeding19 to which is added a hygiene is neglected2. All these changes can decrease in the amount of saliva1,2. The variation favor the increase of plaque, within which spe- observed in the composition of the microbiome cific niches of anaerobiosis are favored where appears to be constant throughout gestation, as some pathogenic species proliferate more eas- shown by DiGiulio et al20, then subsequently by ily. This progression towards a pathological Balan et al21 since this change seems to be caused condition must be prevented not only to pre- mainly by the innate peculiar characteristics of serve the health of the oral cavity but also to each woman. In addition, studies aimed at ana- avoid adverse outcomes in pregnancy30-33. In lyzing the composition of the oral microbiome this regard, a significant species is represented during gestation have shown that in pregnant by the Fusobacterium nucleatum, a commensal women, both in conditions of good oral health bacterium of the oral cavity. It is one of the and in pathological situations, there is an increase most abundant species in the , in pathogenic species. This highlights how the gram-negative, anaerobe, with a possible role modification of the microbiota is the necessary as a modulator of the taste and the odor of starting condition for the onset of an eventual pa- some foods34,35 that, however, could have a thology21. In fact, some bacteria of the microbiota pathological connotation. In reality, F. nuclea- itself would seem to initiate and promote progres- tum is frequently involved in several forms of sion towards periodontal pathology by exacer- periodontal problems2,36. Indeed, the increase bating the host’s immune response22,23. To detect of severity of the periodontal pathology and the this, Balan et al21, found that during pregnancy inflammation corresponds to an increase of the there is an increase in pathogenic taxa in the presence of the bacterium16. Furthermore, this genus Prevotella, Streptococcus and Veillonella, bacterium can also determine systemic effects, contrary to a prevalence of the genus Haemoph- especially adverse effects in pregnancy21.

4581 A. Dessì, A. Bosco, R. Pintus, G. Orrù, V. Fanos

The Placental Microbiome id, which in turn promotes inflammation and the For years the fetal environment has been con- synthesis of prostanoids, potentially responsible sidered sterile but to date, despite numerous for the induction of labor. Therefore, not only the debates37, there are several scientific evidence alterations in the microbiome lead to inflamma- that have demonstrated the presence of a placen- tion, but these alterations can also stimulate the tal microbiome38-42. It is less abundant than the prostanoids to induce preterm labor. The different gut microbiome but very metabolically active, metabolic pathways observed in the microbiomes composed mainly of non-pathogenic commensal of at term and preterm pregnancies may be due phila including: Firmicutes, Tenericutes, Pro- to the different bacterial taxa associated with teobacteria, Bacterioides e Fusobacteria. This the two conditions. In fact, the results show that microbiome appears to be very similar to the oral at term subjects with chorioamnionitis can have microbiome30 given the conspicuous presence of more homogeneous alterations in the microbiome microorganisms such as Fusobacterium, Strepto- of the placental membrane in association with coccus, Prevotella, Neisseria e Porphyromonas. inflammation. Contrary to what is observed in At the basis of this similarity there would be the preterm, in particular those with severe chorio- hypothesis that commensal bacteria of the oral amnionitis, where a high variability in taxa relat- cavity reach the placenta by hematogenous route ed to severe inflammation was found. Neverthe- (low-grade bacteremia). This condition is exacer- less, it was not possible to correlate these altered bated in the presence of pathologies, mainly on metabolisms with the individual bacterial taxa an inflammatory basis, of the oral cavity. Further- detected. In any case, the result is completely new more, this finding would be consistent with the compared to what emerged previously. In fact, it association between some pathogenic species of would seem to highlight that, probably, the tissue the oral cavity and adverse effects in pregnancy alterations found at the placental level are mainly such as , chorioamnionitis, neonatal attributable to an altered bacterial metabolism sepsis, preeclampsia and newborn mortality30-33. rather than the presence of specific taxa43. A different composition of the placental micro- biome has also emerged in preterm vs. full-term The Oral Microbiome of the Newborn pregnancies, further confirming the correlation As mentioned in the previous paragraph, the between the microbiome and fetal health43-45. Fur- microbial colonization would already begin in the thermore, Prince et al43 confirmed both the dif- fetal period. However, immediately after birth, the ferent composition of the placental microbiome infant’s oral microbiome is strongly influenced between at term and preterm pregnancies and the by the surrounding environment. In this scenario, similarity with the oral microbiome and its pos- the contribution of the different microbiomes of sible correlation with adverse effects. Moreover, the mother (vaginal, intestinal and cutaneous), the they detect a different bacterial metabolism in mother’s milk or formula and the infant’s immune presence of chorioamnionites. Indeed, in full- system may be primarily determinant. While, the term pregnancies with chorioamnionitis a de- first foods offered to the baby may be subsequent- crease in the metabolism of butyrate and ribofla- ly determinant50,51. At birth, the first influence vin has been observed. Butyrate has been shown on the oral microbiome of the newborn is due to to suppress inflammation in the gut46-48 and a the type of birth52-54. Indeed, if vaginal birth is decrease in riboflavin has been associated with responsible for a more conspicuous enrichment of an increase in inflammation. Thus, these changes the nascent microbiome with different taxa among in placental bacterial metabolism of full-term which Prevotella, Lactobacillus, Sneathia, Bacte- pregnancies can cause the histological inflamma- rioides and TM7 prevail, the C-section determines tion observed. While, in preterm pregnancies, the a smaller colonization, among which Propionibac- pentose phosphate pathway and the metabolism terium, Corynebacterium, Staphilococcus, Slakia of the glycerophospholipids were significantly e Veillonella predominate55,56. decreased in association with chorioamnionitis. It However, although there is a significant ex- should be noted that glucose is necessary for the posure to a large number of microorganisms, pentose phosphate pathway and in preterm preg- the colonization of the infant’s oral microbiome nancies with chorioamnionitis there is a decrease will follow specific evolutionary stages during in glucose in the amniotic fluid49. Moreover, a de- which only certain species will become resident. crease in the metabolism of the glycerophospho- In any case, the effects of the first colonizations polipids can cause an increase in arachidonic ac- will influence the formation of a complex - ma

4582 Fusobacterium nucleatum and alteration of the oral microbiome ture ecosystem in adulthood54. This necessary the external environment influences this complex maturation process provides in the first months ecological system is scarce57. Just as much as (0-3 months) a rapid colonization, immediately the contribution of genetic heritage should be after birth, by the so-called “pioneer colonizers”. further investigated, on which studies are con- These are normally aerobic or facultative anaer- flicting. On the one hand, some research on twins obic bacteria, including the genus Streptococcus (high-throughput sequencing and fingerprinting spp., Staphylococcus spp. and Actinomyces. They methods)72,73 seem to attribute no role to the ge- facilitate the colonization by other species57, such netic component. On the other hand, other stud- as Fusobacterium to which E. coli, Pseudomo- ies (twin cohort studies)74,75 have highlighted the nas, Lactobacillus crispatus and Lactobacillus possibility of inheriting specific taxa, potentially gasseri are added, through the production and associated with a greater onset of oral cavity excretion of by-products of their metabolism58-60. diseases. The predominance of the genus Streptococcus, especially of S. epidermidis and S. salivarius, is The Role of Fusobacterium Nucleatum due to several factors. One is the abundance of The Fusobacterium nucleatum is a Gram-neg- an optimal substrate for the genus such as the ative anaerobic bacterium, belonging to the Fu- oligosaccharides present in milk togheter with sobacteriaceae family, phylum Fusobacteria. It is the cleavage capacity of immunoglobulins A1 one of the most abundant species in the oral cav- (IgA), abundant in the oral cavity but especial- ity of many human beings76 since birth, suggest- ly in breast milk61,62. They also have the ability ing not only a relevant biological role in the oral to adhere to the mucous membranes to which microbiome but also possible broader spectrum we must add the fact that streptococci are the effects. In fact, research on the first colonizers of most abundant microorganisms in breast milk60. the newborn’s buccal cavity reported the presence Regarding this, Timby et al63 showed that up to of the F. nucleatum already in the first months four months, breastfed babies have a more varied (0-3) with a progressive increase associated with and richer microbiome even if at 12 months this growth56. Furtermore, Angius et al77 aimed at difference is canceled. However, in breastfed in- analyzing the presence and the role of anaerobic fants, specific microbial communities are present bacteria associated to the periodontal pathology even at 12 months, which are totally absent in in mothers and their offspring, highlighted how formula-fed babies, supporting the possible long- 92.5% of the mothers resulted to be positive to term contribution of breastfeeding63. F. nucleatum. Research on biofilm formation has In the following months (3-6 months) the “sec- also highlighted how Fusobacterium nucleatum ond colonizers” appear, such as Granulicatella, evolved in close association not only with human Rothia and Haemophilus. There is a further in- cells and tissues but also in relation to the oral crease in biodiversity with the eruption of the first microbiota. In fact, it would seem to play a key teeth which shows the predominance of different role both in health and in the pathology of the species, such as Streptococcus mutans, Fusobac- buccal cavity78. terium, TM7, SR1, Tenericutes and Synergistetes, more closely related to potentially cariogenic Mutualistic Symbiosis in the Oral Cavity microbiomes64,65. This variation is most likely fa- The direct interactions of Fusobacterium nu- vored by both the appearance of not flaking new cleatum with the tissues of the human body can tissues, the teeth, responsible for the formation vary from a neutral or positive effect, as a sym- of a new specific microbial ecosystem of dental biont of the human oral cavity, to a pathological plaque, and by the influence of the external en- one, as an opportunist78. The positive aspects of vironment66-71. However, this evolution represents the presence of F. nucleatum within the human a fundamental condition for achieving a good oral cavity are inseparable from its role within biodiversity of the oral microbiome, which thus the biofilm. Actually, it showed to have a mutu- becomes more and more varied to be stabilized alistic relationship with the other members of the definitively in the transition to adulthood. Nev- oral microbiome78. Indeed, F. nucleatum plays ertheless, further investigations are needed to a fundamental role, acting both as an essential better understand the influence of the external structural support in the formation of the bio- environment on the oral microbiome. Indeed, film and as a mediator of interactions both with scientific evidence regarding how the oral micro- the microbiota itself and with the host tissues. biome develops during early childhood and how It therefore represents a bridge microorganism

4583 A. Dessì, A. Bosco, R. Pintus, G. Orrù, V. Fanos which, thanks to the particular elongated bacillus responsible for an increase in the bacterium both structure, allows the connection between the first in physiological and pathological conditions85,86. colonizers of , mainly aerobi-fac- While, subjects suffering from severe forms of ultative anaerobes, such as Streptococcus spp. periodontitis and those with uncontrolled type 2 and the “second colonizers”, purely anaerobic, diabetes show a more conspicuous presence of F. including and Aggre- nucleatum87. gatibacter actinomycetemcomitans79 in the for- mation of dental plaque80, a clear example of a Pathogen of the Oral Cavity polymicrobial biofilm. In fact, where there is an The interactions of the Fusobacterium nuclea- absence of Fusobacterium nucleatum, the lack of tum with the host tissues can have pathological “second colonizers” is reported81. characteristics, in fact it is one of the key bacteria Having said that, if on the one hand the elon- in the onset of periodontal pathology. Specifi- gated shape of Fusobacterium nucleatum is cru- cally, understanding the pathogenetic role of F. cial in its function as a “bridge” between the nucleatum can be complex, also considering its different colonizers of the plaque, the presence role as a commensal in the oral cavity88. It can of particular adhesion molecules, adhesins, is in fact mediate, through numerous adhesins89,90, necessary to mediate and directly organize the the colonization and the bacterial dissemination interactions with both the tissues of the host together with other pathogenic periodontium spe- and those among the various components of the cies. At the same time, adhesins can exacerbate microbiota such as, for example, Streptococcus the host response91 favoring the establishment of a mutans and Candida albicans82-84, favoring their highly inflammatory environment by stimulating permanence inside the oral cavity. However, it a massive release of inflammatory cytokines such should be emphasized that, within the biofilm, as IL-6, IL-8 and TNF. Although the virulence there are not only the aforementioned physical factors associated with this bacterium are nu- interactions but also metabolic interactions. Un- merous, there are in fact endotoxins, such as LPS fortunately, data on these phenomena are scarce and some proteases necessary for the antagonism due to the considerable difficulty of reproducing with other bacterial species80, the adhesins seem this complex communication network in vitro and to play a key role. The best knowns are FadA, the few studies on F. nucleatum78. RadD, Fap2 and aid191, responsible for mediating A further implication of the presence of F. Nu- the adhesion both with the host tissues and be- cleatum within the microflora of the oral cavity is tween different bacteria, allowing the formation the modulation of the perception of taste of some of the polymicrobial biofilm. In addition, in the compounds, the cysteine-S-conjugates, present in study by Fardini et al92, it emerged that FadA many vegetables. According to Starkenmann et also behaves as invasion. Indeed, through the al34, it would be the anaerobic component of the link with endothelial vascular cadherins, it can microbiota, especially Fusobacterium nucleatum, increase endothelial permeability favoring sys- the main architect of the transformation of these temic dissemination. A further virulence factor compounds into volatile thiol derivatives. This associated with the presence of adhesins, is the transformation would therefore be responsible for induction of cell death in human lymphocytes a persistent sulfhydryl odor-taste following the by Fap2 and RadD90. It was also highlighted by ingestion of certain foods. It provides another Signat et al88, that the Fusobacterium nucleatum dimension to the taste perception of food34 closely can directly induce the release, by the gingival related to the health of the oral microbiome, in tissue, of particular antimicrobial peptides such turn associated with diet. The study by Angius et as ß-defensins 2. At the same time, this bacterium al77 highlighted how in the mouth of children the be very sensitive to ß-defensins 3 thus showing growth-related increase in F. nucleatum and in a behavior in some ways different from others sulfur compounds could suggest a possible phys- predominantly pathogenic periodontium species. iological role of the bacterium in infants from the Indeed, in conditions of eubiosis it shows a weak first days of life, probably associated with taste action on the immune system and a high sensi- perception. tivity to numerous cytokines93-95. It seems to be Furthermore, there are various scientific ev- part of the commensal bacteria’s task to keep the idence that have highlighted how the presence host’s defenses active without being excessively of Fusobacterium nucleatum is influenced by dangerous. Nevertheless, by acting as a structural numerous external factors. Smoking is in fact “bridge” in the bacterial biofilm, F. nucleatum

4584 Fusobacterium nucleatum and alteration of the oral microbiome can cause an excessive increase in the anaerobic tis101-106. As previously discussed, two factors are flora (second colonizers) favoring the growth of very likely to be decisive: the first concerns the a dysbiotic microflora96. In fact, from the study hormonal changes typical of gestation that ex- by Socransky et al97, in the analysis of more than pose the future mother to an alteration of the oral 13,000 samples of subgingival periodontal plaque, microbiome18 and the second concerns the strong two main groups of bacteria emerged: red and or- similarity observed between the placental and the ange. The red group, consisting of P. gingivalis, oral microbiome30. In 2012, with the aim of evalu- denticola, and , ating the epidemiological evidence on the impact it is characterized by a high pathogenic potential of on adverse pregnancy out- and correlated to clinical indices of periodontal comes and identifying its potential mechanisms, pathology such as pocket depth index (PPD), the first consensus document was drawn up in probing bleeding index (PBI). While the orange synergy between the EFP and the AAP107. To date, one, of which Fusobacterium Nucleatum belongs, compared to the past, the evidence supporting the is decisive both in favoring the colonization by correlation between periodontal pathology and the red group and in determining the progression adverse affects in pregnancy has been strength- of periodontal pathology. It is probable that in ened. The scientific literature of the last century this context of alteration of the microbiome, there regarding the association between adverse effects is both an imbalance towards an inflammatory in pregnancy and F. nucleatum was limited by the state presumably related to an exacerbation of need to use culture media that sometimes do not the host response and to the co-aggregation be- allow the detection of some bacterial species108-110. tween different microbial species. These are both Nevertheless, in recent years, the use of inno- determining factors in the progression towards vative techniques such as 16S-23S rRNA gene periodontal pathology. For example, it has been intergenic transcribed spacer region, has resulted shown that Fusobacterium nucleatum increases in significant progress that has led to a more solid the invasiveness of P. gingivalis98,99. It could be correlation between F. nucleatum and preterm due to a close cooperation between the two spe- birth31,111. It was also possible to highlight the cies, which leads to the escape from the human presence, in the saliva samples of the mother with body’s immune system, and the creation of a preterm birth, of the same strain of F. nucleatum highly inflammatory environment. Studies on found in the gastric aspirate of the newborn112. this synergy are various, however the factors in- These findings also support previous studies on volved seem to be numerous. On the one hand, a the different microbiome observed in term and dysregulation of the inflamosome100 could be the preterm pregnancies113, as discussed above. cause of the excessive reaction triggered by the A further contribution to understand the pos- host organism. However, the creation by F. nu- sible origin of the detected infections and the un- cleatum of lipid rafts through which it allows the derlying mechanisms was provided by preclinical entry of P. gingivalis into the cells of the human studies on murine specimens, thanks to which it body98 seems to be only one of the mechanisms was possible to highlight how adhesin-invasin Fa- through which F. Nucleatum mediates the host in- dA mediates the crossing of the placental barrier. vasion by other pathogens. Despite the abundant Indeed, to date, years after the first consensus literature, there are still numerous mechanisms document of the EFP and the AAP from which to be clarified. Therefore, as emerged from the two possible mechanisms underlying the placen- study by Tefiku et al91, certainly F. nucleatum tal infection emerged, the hypothesis of hema- plays a key role in pathologies of the oral cavity, togenous dissemination of oral microorganisms however it is not possible to state with certainty and their metabolites seems to prevail with con- whether its role is dominant or secondary. sequent immune and inflammatory reaction at the level of the fetal-placental unit114. Even stillbirths Correlation with Adverse Affects in and the chorioamnionites30,32,115,116 were related to Pregnancy and Systemic Pathologies the presence of F. nucleatum. In 2010, Han et al30 The correlation between Fusobacterium nu- have in fact described the first case of neonatal cleatum and adverse affects in pregnancy is sup- mortality in the presence of chorioamnionitis ported by numerous scientific evidence16,19, like- associated with Fusobacterium nucleatum. They wise there are numerous researches that correlate ascertained the oral origin of the infection found poor oral health to abortions, neonatal mortality, at the level of the fetal-placental unit, correlating preterm births, preeclampsia and chorioamnioni- it with a weakening of the immune defenses as-

4585 A. Dessì, A. Bosco, R. Pintus, G. Orrù, V. Fanos sociated with a respiratory infection contracted microbiota in a dual function. In the first instance by the woman a few days earlier. The role of the the taste perception and consequently food choic- weakening of the host’s immune defenses, related es, nutrition, and eating behavior. But, in another to the fact that many infections are actually much perspective, this interaction acts as the mediation more complex than previously thought due to the of infective respiratory and oral diseases; in par- possible polymicrobial origin28, suggests that the ticular, significant evidence is recently reported for commensal bacteria as well as the interactions the bitter taste receptors T2R. These receptors are between various microorganisms can have a deci- commonly present in the oral cavity where they sive impact on both the development of virulence signal in the presence of toxic substances. For ex- and the outcome of the infection. ample, T2R38 regulates innate-immune responses Finally, other adverse effects in pregnancy in the oral and nasal mucosa due to microbial prod- potentially related to the presence of F. nuclea- ucts. These molecular structures are induced in the tum such as neonatal sepsis117 and preeclampsia118 release of antimicrobial peptides and cytokines in have been found but they need further studies19. response to different oral bacteria metabolites. In Table I summarizes the main studies regard- the gingival epithelia Fn-T2R38 interaction causes ing the association between Fusobacterium nu- the release of high levels of beta-defensin-2 (hBD- cleatum and its possible adverse effects during 2)138. In addition, the secretion of AMPs has been pregnancy. evaluated, to prevent overgrowth of oral bacteria As reported in a recent review16 the Fusobacte- and regulate the microbial composition, avoiding rium nucleatum is also associated with numerous a dysbiotic profile in the tissues. For this reason, systemic pathologies such as some pathologies of Sandell et al139 reported that genetic variation in the gastro-intestinal tract including inflammatory the bitter taste receptor T2R38 taste genotype bowel disease119,120, IBD, colorectal cancer121-126, reflected in the microbial composition of oral mu- CRC, and appendicitis127-129. It has also been cosa in subjects from different geographical areas. found in atherosclerotic plaques130-132. It has been Douglas et al140, showed an interesting role of related also to rheumatoid arthritis133, to Alzhei- oral Gram-negative bacteria in T2Rs activation mer’s disease134, to Lemierre’s syndrome135, to by bitter bacterial byproducts in the upper airway. brain aneurysms136 and to some respiratory tract Gram-negative bacteria produce acyl-homoserine infections135. lactones (AHLs), which bind to and activate T2Rs It is therefore clear how this pathogen can sys- located in solitary chemosensory cells or in cili- tematically spread in numerous districts of the ate epithelial cells. This activates a biochemistry organism. It could be due to the high adhesive pathway that increases the nitric oxide (NO) pro- capacity and to the different virulence mecha- duction by the nitric oxide synthase (NOS), which nisms, however it is clear how its presence and both directly kills bacteria and enhances ciliary its dissemination are closely associated with the beating. Furthermore, the taste receptor intracel- state of health of the individual. lular signaling yields increased of Ca2+, via gap junctions. This cation diffuses into adjacent ciliat- F. Nucleatum and Bitter Taste Receptors ed cells with a consequent increase of antimicrobi- The role of the gut microbiome as a modulator al AMP secretion (Figure 1). of human food preferences has been suggested by In this context, F. nucleatum could be admitted different authors, but the evidence with oral micro- as an early oral colonizer on the first day of life, biota remains poorly defined, even if is known that because it could stimulate the innate immune the oral microbe community is strongly affected response of the newborns against oral as well as by human dietary habits. In this context, recent respiratory pathogens. studies on dental calculi, indicate a significant difference in the periodontal bacteria titer between The Bacteria of The Oral Cavity: Possible samples from preindustrial-era and modern ones137. Implications in Infection by SARS-COV-2 The data suggest that socioeconomic conditions The oral cavity certainly represents a strategic and different alimentary habits have determined location as an excellent entrance and exit gates a significant increase of periodontal pathogens in for all the pathogenic species responsible for recent tooth biofilm. This discrepancy could be respiratory tract infections and therefore also for linked to the noticeable increase in degenerative Sars-Cov-2 infection, especially considering its diseases in the modern age. Recently, the taste detection in saliva samples and the abundance of receptor system has been related to oral-nasal ACE2 receptors in the epithelium of the buccal

4586 Fusobacterium nucleatum and alteration of the oral microbiome

Table I. Fusobacterium Nucleatum and adverse pregnancy outcomes. Results Technique Sample Author Year

First associations between Culture Amniotic fluid from 45 selected Miller et al110 1980 F. Nucleatum and preterm birth patients 33 patients with singleton Wahbeh et al109 1984 pregnancies 773 transabdominal amniocenteses Chaim et al108 1992 from women presenting with preterm labor and intact membranes

F. Nucleatum has been observed 16SrRNA-based Samples of fetal membranes Cahill et al111 2005 in preterm birth and preterm culture from 37 preterm infants, and premature rupture of indipendent 6 normal term controls delivered membranes (PPROM) by caesarean section Associations between Amniotic fluid specimens from Han et al31 2009 F. Nucleatum and preterm 46 pregnancies complicated by birth was observed PTB and 16 asymptomatic

Associations between PCR 3 women in preterm labor Gauthier et al106 2011 F. Nucleatum and preterm with intact membranes birth was confirmed and suggestion that intra-amniotic F. nucleatum could originate from the patient’s or the partner’s oral microflora

Association between F. Nucleatum 16SrRNA-based 44 patients with singleton Wang et al117 2013 and preterm birth has beem culture pregnancies condirmed and a novel association indipendent + between F. Nucleatum and culture neonatal sepsis has been observed

Association between F. Nucleatum and preterm birth Culture Case reports of 1 pregnant woman Dixon et al115 1994 and choriomamnionitis that have been probably due to an ascending infection after orogenital contact.

Association between F. Nucleatum Culture Case reports of 1 pregnant woman Boher et al32 2012 and choriomamnionitis at term with potential adverse maternal and neonatal outcome

Association between F. Nucleatum 16SrRNA-based Case study of a pregnant with Han et al30 2010 and stillbirth with culture associated gingivitis choriomamnionitis indipendent Association between high serum Enzyme-linked 786 serum samples at baseline; Ebersole et al116 2009 antibody levels to F. Nucleatum immunosorbent this was reduced to 635 by the and stillbirth assay 29- to 32-week visit; 620 matched samples were available for within- and between-patient comparisons of changes between baseline and 29 to 32 weeks

First association between PCR 16 placentas’ samples obtained Barak et al118 2007 F. Nucleatum and hypertensive from cesarean sections of women disorders that may suggest a with preeclampsia and from possible contribution of 14 age-matched healthy periopathogenic pregnant women.

4587 A. Dessì, A. Bosco, R. Pintus, G. Orrù, V. Fanos

Figure 1. Schematic representation of innate antimicrobial activity by Gram negative bacteria stimulation of T2R receptors. cavity141. Furthermore, the possible correlation membranes142. Zheng et al143 have highlighted between periodontal pathogenic microorganisms how in the most serious patients with Covid-19 and the pathogenesis of respiratory infections has there was an increase in neutrophils and low lev- long been known142. In this regard, several studies els of lymphocytes, an abnormal condition for a have shown how the oral cavity can be crucial viral infection, compared to less severe patients. in the respiratory tract infection process and It was therefore assumed that the high level of several possible mechanisms have in fact been neutrophils was to be associated with a bacterial proposed as the basis of the etiopathogenesis. co-infection. While the low level of lymphocytes, The first concerns the aspiration into the lungs essential in the course of an immune response of typically of the oral cavity against viral species, was due to a functional such as P. gingivalis or A. actinomycetemcom- exhaustion of the lymphocytes themselves or to itans, which are abundant in subjects suffering the prevarication of bacterial co-infection143. As from periodontitis, resulting in lung infections. A a confirmation of this, it would seem to be the second mechanism proposed, concerns the mod- study by Zhou et al144, which found that 50% of ification of the oral mucous membranes induced those who died from Covid-19 had a secondary by inflammation. It results from the periodontal bacterial infection. To this must be added what pathology, which would make them more suscep- emerged from the study by Cox et al145 about the tible to adhesion and colonization by pathogenic relevance at the level of clinical indices and mor- species of the respiratory tract. This would be tality of the co-infections in patients affected by followed by their possible aspiration into the Covid-19. Probably in the light of these data, Patel lungs. These changes in the oral mucosa can also and Sampson146 hightlighted the possible impact extend to the respiratory epithelium, making it of oral bacteria in Covid-19 co-infections. In fact, more susceptible to infections, a possible further thanks to very recent metagenomic analyzes147, pathogenetic mechanism. Finally, it has also been the presence in patients suffering from severe hypothesized that the inflammatory state asso- acute respiratory syndrome 2 of a high number ciated with periodontal pathology destroys the of cariogenic and periodontopathogenic bacte- salivary film that covers the pathogenic bacte- ria, including the Fusobacterium, has frequently ria, hindering their elimination from the mucous emerged, confirming the thesis that correlates

4588 Fusobacterium nucleatum and alteration of the oral microbiome oral dysbiosis and the possible complications of a fertile ground for Covid-19 infection which Covid-19. However, the studies concerning the destabilized the immune system and allowed the influence of Sars-CoV-2 on the microbiome are onset of bacteremia, or whether Sars-Cov-2 itself very limited, but it is curious to note, as report- is responsible for the dysbiosis which, following ed by Bao et al148 that other investigations on the strong impact on the immune system, in some animal models of the swine epidemic diarrhea patients, can lead to bacteremia. Finally, it should virus, belonging to the coronavirus family, have be noted that both Sars-Cov-2 and F. nucleatum shown a high presence of the Fusobacterium have direct and indirect repercussions on the in affected subjects. Indeed, as pointed out by olfactory-gustatory system, respectively. In the several scientific investigations146,148,149, there are case of Covid-19 infection, a significant percent- several studies that suggest both the involvement age of patients reported anosmia or hyposmia of periodontopathogenic species in the pathogen- as a preliminary symptom155. In any case, this esis of the respiratory infections, such as Sars- type of alterations seems to be transitory with Cov2, and their correlation to various systemic a complete or partial recovery in a few weeks, diseases, including hypertension, cardiovascular however there are still no reliable data156. The diseases and diabetes. Furthermore, these pa- origin of the dysfunction seems to be mainly at- thologies have emerged as a frequent cause of tributed to an involvement at the central level of comorbidities associated with an increased risk of the olfactory bulb and only partially to peripheral serious complications and death from Covid-19. damage at the level of the olfactory epithelium. Given the numerous studies on the effectiveness The alteration of taste seems to be secondary to of improving oral health on clinical indices and the olfactory dysfunction. Therefore, the role of mortality in patients with pneumonia150,151 as well Fusobacterium nucleatum in the modulation of as reducing the use of mechanical ventilation152 gustatory perception, as well as its interference in but also the preventive role of a good oral health the oral-nasal mucosal immunity by taste recep- on pneumonia and respiratory tract infections in tors interaction, must be strongly investigated in elderly hospitalized or nursing home patients153 it COVID-19 patients. could be assumed that the same benefits could be obtained in patients with Sars-Cov-2. In addition to this, on the one hand, the pulmonary hypoxia Discussion that some patients with Covid-19 undergo can favor a lung environment more prone to coloni- From the analysis of the literature, it is clear zation by anaerobic bacteria. While, on the other that the homeostasis of the oral microbiome rep- hand, given the respiratory difficulties of some resents a key point for human health with local subjects, the mechanical ventilation is often asso- and systemic implications. In this context, the ciated with the onset of secondary pneumonia148. Fusobacterium nucleatum plays a crucial role In this regard, promoting good oral health thanks to its structural and organizational func- is essential for maintaining the eubiosis of the tion within the microflora of the buccal cavity microbiome since a simple dysbiosis can affect in order to maintain the homeostasis. In fact, as the onset of co-infections. In fact, normal daily previously discussed, studies on the oral microbi- activities, including chewing and normal oral ome of children assume a possible physiological hygiene practices, cause micro-lesions inside the role of F. nucleatum from the first days of life. buccal cavity that can lead to bacteremia, through However, in particular conditions both patho- the hematogenous dissemination of oral bacteria logical and non-pathological, its strong adhesive and their inflammatory metabolites, with possible and invasive capacities result in an easy systemic systemic inflammation in certain patients146. As dissemination in the body, also increasing very a confirmation of the importance of the eubiosis often the virulence of other pathogens through of the oral microbiota there is the study of Wolff various mechanisms. In fact, it has been dis- et al154 which reports 4 cases of F. nucleatum cussed how it can favor the escape from the bacteremia in patients with Covid-19 without host’s immune defenses, facilitate the crossing the patients having known risk factors for Fu- of the epithelia and exacerbate the defensive re- sobacterium nucleatum infection. Therefore, the sponse in the human being. These data suggest question arises whether the oral dysbiosis po- underlying polymicrobial pathologies. In fact, the tentially caused by various antecedent factors, most recent diagnostic investigation technologies including stress and poor nutrition, has created have allowed us to ascertain that many infections

4589 A. Dessì, A. Bosco, R. Pintus, G. Orrù, V. Fanos are actually much more complex than originally Conflict of Interest believed. Therefore, it appears clear that in an The Authors declare that they have no conflict of interests. infection, despite often focusing on the dominant microbial species, other microorganisms, includ- ing commensals, can have an important impact both on the pathogenesis of the disease itself and References on the outcomes. Furthermore, the examined data revealed that sometimes the outcomes of 1) Kilian M, Chapple IL, Hannig M, Marsh PD, Meuric the presence of a microorganism are determined V, Pedersen AM, Tonetti MS, Wade WG, Zaura E. not uniquely by the specific characteristics of the The oral microbiome - an update for oral health- care professionals. Br Dent J 2016; 221: 657-666. single species but by the interaction of the various micro-organisms present. They can thus modify 2) Yenen Z, Ataçağ T. Oral care in pregnancy. J Turk Ger Gynecol Assoc 2019; 20: 264-268. their own metabolism, virulence and cause an 3) Kamaraj DR, Bhushan KS, Laxman VK, Mathew important alteration to the surrounding environ- J. Detection of odoriferous subgingival and ment resulting in damage to the host’s tissues. tongue microbiota in diabetic and nondiabetic pa- It could be interesting to analyze the cor- tients with oral malodor using polymerase chain relation between Sars-Cov-2 and Fusobacterium reaction. Indian J Dent Res 2011; 22: 260-265. nucleatum both to evaluate a possible broad-spec- 4) 4)Deo PN, Deshmukh R. Oral microbiome: un- trum preventive action, in favor of all subjects veiling the fundamentals. J Oral Maxillofac Pathol for whom, by promoting the eubiosis of the oral 2019; 23: 122-128. microbiome, a defensive action promoted by the 5) Perera M, Al-Hebshi NN, Speicher DJ, Perera I, commensal bacteria themselves, but, above all, Johnson NW. Emerging role of bacteria in oral carcinogenesis: a review with special reference to for patients with specific comorbidities and there- perio-pathogenic bacteria. J Oral Microbiol 2016; fore already prone to oral dysbiosis. In addition 8:32762. to this, after the infection, a possible interven- 6) Delitto AE, Rocha F, Decker AM, Amador B, So- tion on the oral microbiome could represent an renson HL, Wallet SM. MyD88-mediated innate improvement in the prognosis, avoiding possible sensing by oral epithelial cells controls periodontal co-infections. In addition, as regards non-patho- inflammation. Arch Oral Biol 2018; 87: 125-130. logical clinical conditions that are still affected 7) Yang D, Chertov O, Bykovskaia SN, Chen Q, by an alteration of the microbiome such as preg- Buffo MJ, Shogan J, Anderson M, Schröder JM, nant women, a preventive intervention on the Wang JM, Howard OM, Oppenheim JJ. Beta-de- fensins: linking innate and adaptive immunity microflora of the oral cavity could boast even through dendritic and T cell CCR6. Science 1999; greater benefits, not only for what concerns the 286: 525-528. prevention of adverse effects typically associated 8) Kagnoff MF, Eckmann L. Epithelial cells as sen- with oral dysbiosis but also for respiratory tract sors for microbial infection. J Clin Invest 1997; infections, in this case by Sars-Cov-2. Further- 100: 6-10. more, from the assessment of the correlation 9) Krisanaprakornkit S, Kimball JR, Weinberg A, between Covid-19 and F. nucleatum, the role of Darveau RP, Bainbridge BW, Dale BA. Inducible other microorganisms could emerge that, through expression of human beta-defensin 2 by Fuso- specific, synergistic, additive, or antagonistic ac- bacterium nucleatum in oral epithelial cells: mul- tiple signaling pathways and role of commensal tions, could prevent or favor Sars-Cov-2 infection bacteria in innate immunity and the epithelial bar- or in any case affect its outcomes. rier. Infect Immun 2000; 68: 2907-2915. 10) Mohammed H, Varoni EM, Cochis A, Cordaro M, Gallenzi P, Patini R, Staderini E, Lajolo C, Rimon- dini L, Rocchetti V. Oral dysbiosis in pancreatic Conclusions cancer and liver cirrhosis: a review of the litera- ture. Biomedicines 2018; 6: 115. In summary, it may be assumed that the prob- 11) Patini R. Oral microbiota: discovering and fac- lems of the olfactory and gustatory system can be ing the new associations with systemic diseases. Pathogens 2020; 9: 313. synergistic or additive and therefore in order to favor a complete recovery, given the long sequel- 12) Martellacci L, Quaranta G, Patini R, Isola G, Gal- lenzi P, Masucci L. A literature review of metage- ae reported by some patients, the establishment of nomics and culturomics of the peri-implant micro- a new balance within the oral microbiome could biome: current evidence and future perspectives. be decisive. Materials 2019; 12: 3010.

4590 Fusobacterium nucleatum and alteration of the oral microbiome

13) Patini R. Culturomics: a new approach for the di- 27) Patini R, Staderini E, Lajolo C, Lopetuso L, Mo- agnosis of the oral microbiota. Dental Hypothe- hammed H, Rimondini L, Rocchetti V, Franceschi ses 2020; 11: 72-73 F, Cordaro M, Gallenzi P. Relationship between 14) Martellacci L, Quaranta G, Fancello G, D’Addo- oral microbiota and periodontal disease: a sys- na A, Sanguinetti M, Patini R, Masucci L. Char- tematic review. Eur Rev Med Pharmacol Sci 2018; acterizing peri-implant and sub-gingival microbio- 220: 5775-5788. ta through culturomics. first isolation of some spe- 28) Short FL, Murdoch SL, Ryan RP. Polybacteri- cies in the oral cavity. A pilot study. Pathogens al human disease: the ills of social networking. 2020; 9: 365. Trends Microbiol 2014; 22: 508-516. 15) Wade WG. The oral microbiome in health and 29) Hajishengallis G, Darveau RP, Curtis MA. The disease. Pharmacol Res 2013; 69: 137-143. keystone-pathogen hypothesis. Nat Rev Microbi- 16) Han YW. Fusobacterium nucleatum: a commen- ol 2012; 10: 717-725. sal-turned pathogen. Curr Opin Microbiol 2015; 30) Han YW, Fardini Y, Chen C, Iacampo KG, Per- 23: 141-147. aino VA, Shamonki JM, Redline RW. Term still- 17) Patini R, Cattani P, Marchetti S, Isola G, Quaran- birth caused by oral Fusobacterium nucleatum. ta G, Gallenzi P. Evaluation of predation capabil- Obstet Gynecol 2010; 115: 442-445. ity of periodontopathogens bacteria by bdellovib- 31) Han YW, Shen T, Chung P, Buhimschi IA, Buhim- rio bacteriovorus HD100. An in vitro study. Mate- schi CS. Uncultivated bacteria as etiologic agents rials 2019; 12: 2008. of intra-amniotic inflammation leading to preterm 18) Amir M, Brown JA, Rager SL, Sanidad KZ, Anan- birth. J Clin Microbiol 2009; 47: 38-47. thanarayanan A, Zeng MY. Maternal microbi- 32) Bohrer JC, Kamemoto LE, Almeida PG, Oga- ome and infections in pregnancy. Microorgan- sawara KK. Acute chorioamnionitis at term isms 2020; 8: E1996. caused by the oral pathogen Fusobacterium nu- 19) Vander Haar EL, So J, Gyamfi-Bannerman C, cleatum. Hawaii J Med Public Health 2012; 71: Han YW. Fusobacterium nucleatum and adverse 280-281. pregnancy outcomes: epidemiological and mech- 33) Wang X, Buhimschi CS, Temoin S, Bhandari V, anistic evidence. Anaerobe 2018; 50: 55-59. Han YW, Buhimschi IA. Comparative microbial 20) DiGiulio DB, Callahan BJ, McMurdie PJ, Costello analysis of paired amniotic fluid and cord blood EK, Lyell DJ, Robaczewska A, Sun CL, Goltsman from pregnancies complicated by preterm birth DS, Wong RJ, Shaw G, Stevenson DK, Holmes and early-onset neonatal sepsis. PLoS One 2013; SP, Relman DA. Temporal and spatial variation 8: e56131. of the human microbiota during pregnancy. Proc 34) Starkenmann C, Le Calvé B, Niclass Y, Cayeux Natl Acad Sci U S A 2015; 112: 11060-11065. I, Beccucci S, Troccaz M. Olfactory perception 21) Balan P, Chong YS, Umashankar S, Swarup S, of cysteine-S-conjugates from fruits and vegeta- Loke WM, Lopez V, He HG, Seneviratne CJ. Key- bles. J Agric Food Chem 2008; 56: 9575-9580. stone species in pregnancy gingivitis: a snapshot 35) Orrù G, Palmas G, Denotti G, Fais S, Angius of oral microbiome during pregnancy and post- S, Pichiri G, Coni P, Coghe F, Noto A, Dessì A, partum period. Front Microbiol 2018; 9: 2360. Fanos V. Incidence of fusobacterium nucleatum 22) Liu J, Tang X, Li C, Pan C, Li Q, Geng F, Pan Y. in tongue biofilm of mothers and newborns. A Porphyromonas gingivalis promotes the cell cy- new way for the olfactory perception? Selected cle and inflammatory cytokine production in peri- Abstracts of the 11th International Workshop on odontal ligament fibroblasts. Arch Oral Biol 2015; Neonatology, Cagliari (Italy). J Pediatr Neonat In- 60: 1153-1161. dividual Med 2015; 4: e040249. 23) Li Y, Guo H, Wang X, Lu Y, Yang C, Yang P. Coin- 36) Whitmore SE, Lamont RJ. Oral bacteria and can- fection with Fusobacterium nucleatum can en- cer. PLoS Pathog 2014; 10: e1003933. hance the attachment and invasion of Porphyro- 37) Lauder AP, Roche AM, Sherrill-Mix S, Bailey A, monas gingivalis or Aggregatibacter actinomyce- Laughlin AL, Bittinger K, Leite R, Elovitz MA, Par- temcomitans to human gingival epithelial cells. ry S, Bushman FD. Comparison of placenta sam- Arch Oral Biol 2015; 60: 1387-1393. ples with contamination controls does not provide 24) Bik EM, Long CD, Armitage GC, Loomer P, Em- evidence for a distinct placenta microbiota. Mi- erson J, Mongodin EF, Nelson KE, Gill SR, Fras- crobiome 2016; 4: 29. er-Liggett CM, Relman DA. Bacterial diversity in 38) Aagaard K, Ma J, Antony KM, Ganu R, Petrosi- the oral cavity of 10 healthy individuals. ISME J no J, Versalovic J. The placenta harbors a unique 2010; 4: 962-974. microbiome. Sci Transl Med 2014; 6: 237ra65. 25) Aas JA, Paster BJ, Stokes LN, Olsen I, Dewhirst 39) Zheng J, Xiao X, Zhang Q, Mao L, Yu M, Xu J. FE. Defining the normal bacterial flora of the oral The placental microbiome varies in association cavity. J Clin Microbiol 2005; 43: 5721-5732. with low birth weight in full-term neonates. Nutri- 26) Lin W, Jiang W, Hu X, Gao L, Ai D, Pan H, Niu C, ents 2015; 7: 6924-6937. Yuan K, Zhou X, Xu C, Huang Z. Ecological shifts 40) Bassols J, Serino M, Carreras-Badosa G, Burcelin of supragingival microbiota in association with R, Blasco-Baque V, Lopez-Bermejo A, Fernan- pregnancy. Front Cell Infect Microbiol 2018; 8: 24. dez-Real JM. Gestational diabetes is associated

4591 A. Dessì, A. Bosco, R. Pintus, G. Orrù, V. Fanos

with changes in placental microbiota and micro- 53) Lif Holgerson P, Harnevik L, Hernell O, Tanner AC, biome. Pediatr Res 2016; 80: 777-784. Johansson I. Mode of birth delivery affects oral mi- 41) Zheng J, Xiao X, Zhang Q, Mao L, Yu M, Xu crobiota in infants. J Dent Res 2011; 90: 1183-1188. J, Wang T. The placental microbiota is altered 54) Hegde S, Munshi AK. Influence of the maternal among subjects with gestational diabetes melli- vaginal microbiota on the oral microbiota of the tus: a pilot study. Front Physiol 2017; 8: 675. newborn. J Clin Pediatr Dent 1998; 22: 317-321. 42) Zheng J, Xiao XH, Zhang Q, Mao LL, Yu M, Xu 55) Gomez A, Nelson KE. The oral microbiome of chil- JP, Wang T. Correlation of placental microbio- dren: development, disease, and implications be- ta with fetal macrosomia and clinical characteris- yond oral health. Microb Ecol 2017; 73: 492-503. tics in mothers and newborns. Oncotarget 2017; 56) Xiao J, Fiscella KA, Gill SR. Oral microbiome: 8: 82314-82325. possible harbinger for children’s health. Int J Oral 43) Prince AL, Ma J, Kannan PS, Alvarez M, Gisslen Sci 2020; 12: 12. T, Harris RA, Sweeney EL, Knox CL, Lam- 57) Dzidic M, Collado MC, Abrahamsson T, Artacho bers DS, Jobe AH, Chougnet CA, Kallapur SG, A, Stensson M, Jenmalm MC, Mira A. Oral micro- Aagaard KM. The placental membrane microbi- biome development during childhood: an ecolog- ome is altered among subjects with spontaneous ical succession influenced by postnatal factors preterm birth with and without chorioamnionitis. and associated with tooth decay. ISME J 2018; Am J Obstet Gynecol 2016; 214: 627.e1-627.e16. 12: 2292-2306. 44) Amarasekara R, Jayasekara RW, Senanayake H, 58) Ward TL, Hosid S, Ioshikhes I, Altosaar I. Human Dissanayake VH. Microbiome of the placenta in milk metagenome: a functional capacity analysis. pre-eclampsia supports the role of bacteria in the BMC Microbiol 2013; 13: 116. multifactorial cause of pre-eclampsia. J Obstet 59) Martín R, Langa S, Reviriego C, Jimínez E, Marín Gynaecol Res 2015; 41: 6629. ML, Xaus J, Fernández L, Rodríguez JM. Human 45) Pelzer E, Gomez-Arango LF, Barrett HL, Nitert milk is a source of lactic acid bacteria for the in- MD. Review: maternal health and the placental fant gut. J Pediatr 2003; 143: 754-758. microbiome. Placenta 2017; 54: 30-37. 60) Jost T, Lacroix C, Braegger C, Chassard C. As- 46) Zimmerman MA, Singh N, Martin PM, Thangara- sessment of bacterial diversity in breast milk us- ju M, Ganapathy V, Waller JL, Shi H, Robertson ing culture-dependent and culture-independent KD, Munn DH, Liu K. Butyrate suppresses colonic approaches. Br J Nutr 2013; 110: 1253-1262. inflammation through HDAC1-dependent Fas up- 61) Cole MF, Evans M, Fitzsimmons S, Johnson J, regulation and Fas-mediated apoptosis of T cells. Pearce C, Sheridan MJ, Wientzen R, Bowden G. Am J Physiol Gastrointest Liver Physiol 2012; Pioneer oral streptococci produce immunoglobulin 302: G1405-1415. A1 protease. Infect Immun 1994; 62: 2165-2168. 47) Vinolo MA, Rodrigues HG, Nachbar RT, Curi R. 62) Hanson LA, Söderström T. Human milk: defense Regulation of inflammation by short chain fatty against infection. Prog Clin Biol Res 1981; 61: 147-159. acids. Nutrients 2011; 3: 858-876. 63) Timby N, Domellöf M, Holgerson PL, West CE, 48) Segain JP, Raingeard de la Blétière D, Bourreille Lönnerdal B, Hernell O, Johansson I. Oral microbi- A, Leray V, Gervois N, Rosales C, Ferrier L, Bon- ota in infants fed a formula supplemented with bo- net C, Blottière HM, Galmiche JP. Butyrate inhib- vine milk fat globule membranes - a randomized its inflammatory responses through NFkappaB controlled trial. PLoS One 2017; 12: e0169831. inhibition: implications for Crohn’s disease. Gut 64) Merglova V, Polenik P. Early colonization of the 2000; 47: 397-403. oral cavity in 6- and 12-month-old infants by car- 49) Buhimschi CS, Dulay AT, Abdel-Razeq S, Zhao iogenic and periodontal pathogens: a case-con- G, Lee S, Hodgson EJ, Bhandari V, Buhimschi IA. trol study. Folia Microbiol 2016; 61: 423-429. Fetal inflammatory response in women with pro- 65) Wan AK, Seow WK, Purdie DM, Bird PS, Walsh teomic biomarkers characteristic of intra-amniotic LJ, Tudehope DI. Oral colonization of Streptococ- inflammation and preterm birth. BJOG 2009; 116: cus mutans in six-month-old predentate infants. J 257-267. Dent Res 2001; 80: 2060-2065. 50) Isolauri E. Development of healthy gut microbiota 66) Lif Holgerson P, Öhman C, Rönnlund A, Johans- early in life. J Paediatr Child Health 2012; 48 Sup- son I. Maturation of oral microbiota in children pl 3:1-6. with or without dental caries. PLoS One 2015; 10: 51) Munyaka PM, Khafipour E, Ghia JE. External in- e0128534. fluence of early childhood establishment of gut 67) Cephas KD, Kim J, Mathai RA, Barry KA, Dowd microbiota and subsequent health implications. SE, Meline BS, Swanson KS. Comparative anal- Front Pediatr 2014; 2: 109. ysis of salivary bacterial microbiome diversity in 52) Dominguez-Bello MG, Costello EK, Contreras M, edentulous infants and their mothers or prima- Magris M, Hidalgo G, Fierer N, Knight R. Delivery ry care givers using pyrosequencing. PLoS One mode shapes the acquisition and structure of the 2011; 6: e23503. initial microbiota across multiple body habitats in 68) Yang F, Zeng X, Ning K, Liu KL, Lo CC, Wang W, newborns. Proc Natl Acad Sci U S A 2010; 107: Chen J, Wang D, Huang R, Chang X, Chain PS, 11971-11975. Xie G, Ling J, Xu J. Saliva microbiomes distin-

4592 Fusobacterium nucleatum and alteration of the oral microbiome

guish caries-active from healthy human popula- terium nucleatum ssp. polymorphum. Mol Oral tions. ISME J 2012; 6: 1-10. Microbiol 2017; 32: 355-364. 69) Struzycka I. The oral microbiome in dental caries. 83) Kaplan CW, Lux R, Haake SK, Shi W. The Fu- Pol J Microbiol 2014; 63: 127-135. sobacterium nucleatum outer membrane protein 70) Rôças IN, Alves FR, Rachid CT, Lima KC, RadD is an arginine-inhibitable adhesin required Assunção IV, Gomes PN, Siqueira JF Jr. Micro- for inter-species adherence and the structured ar- biome of deep dentinal caries lesions in teeth chitecture of multispecies biofilm. Mol Microbiol with symptomatic irreversible . PLoS One 2009; 71: 35-47. 2016; 11: e0154653. 84) Wu T, Cen L, Kaplan C, Zhou X, Lux R, Shi W, He 71) Crielaard W, Zaura E, Schuller AA, Huse SM, X. Cellular components mediating coadherence Montijn RC, Keijser BJ. Exploring the oral micro- of Candida albicans and Fusobacterium nuclea- biota of children at various developmental stages tum. J Dent Res 2015; 94: 1432-1438. of their dentition in the relation to their oral health. 85) Mason MR, Preshaw PM, Nagaraja HN, Dabdoub BMC Med Genomics 2011; 4: 22. SM, Rahman A, Kumar PS. The subgingival mi- 72) Stahringer SS, Clemente JC, Corley RP, Hewitt crobiome of clinically healthy current and never J, Knights D, Walters WA, Knight R, Krauter KS. smokers. ISME J 2015; 9: 268-272. Nurture trumps nature in a longitudinal survey of 86) Moon JH, Lee JH, Lee JY. Subgingival micro- salivary bacterial communities in twins from ear- biome in smokers and non-smokers in Korean ly adolescence to early adulthood. Genome Res patients. Mol Oral Microbiol 2012; 22: 2146-2152. 2015; 30: 227-241. 73) Papapostolou A, Kroffke B, Tatakis DN, Nagara- 87) Casarin RC, Barbagallo A, Meulman T, Santos ja HN, Kumar PS. Contribution of host genotype VR, Sallum EA, Nociti FH, Duarte PM, Casati MZ, to the composition of health-associated supragin- Gonçalves RB. Subgingival biodiversity in subjects gival and subgingival microbiomes. J Clin Peri- with uncontrolled type-2 diabetes and chronic peri- odontol 2011; 38: 517-524. odontitis. J Periodontal Res 2013; 48: 30-36. 74) Corby PM, Bretz WA, Hart TC, Schork NJ, Wes- 88) Signat B, Roques C, Poulet P, Duffaut D. Fuso- sel J, Lyons-Weiler J, Paster BJ. Heritability of oral bacterium nucleatum in periodontal health and microbial species in caries-active and caries-free disease. Curr Issues Mol Biol 2011; 13: 25-36. twins. Twin Res Hum Genet 2007; 10: 821-828. 89) Kaplan A, Kaplan CW, He X, McHardy I, Shi W, 75) Corby PM, Bretz WA, Hart TC, Filho MM, Oliveira Lux R. Characterization of aid1, a novel gene in- B, Vanyukov M. Mutans streptococci in preschool volved in Fusobacterium nucleatum interspecies twins. Arch Oral Biol 2005; 50: 347-351. interactions. Microb Ecol 2014; 68: 379-387. 76) Griffen AL, Beall CJ, Campbell JH, Firestone ND, 90) Kaplan CW, Ma X, Paranjpe A, Jewett A, Lux R, Kumar PS, Yang ZK, Podar M, Leys EJ. Distinct Kinder-Haake S, Shi W. Fusobacterium nuclea- and complex bacterial profiles in human peri- tum outer membrane proteins Fap2 and RadD in- odontitis and health revealed by 16S pyrose- duce cell death in human lymphocytes. Infect Im- quencing. ISME J 2012; 6: 1176-1185. mun 2010; 78: 4773-4778. 77) Angius S, Fais S, Casula E, Contu MP, Coghe F, 91) Tefiku U, Popovska M, Cana A, Zendeli-Bedxeti Fanos V, Orrù G, The first days of life: incidence of L, Recica B, Spasovska-Gjorgovska A, Spasovs- the commensal-turned pathogen Fusobacterium ki S. Determination of the role of Fusobacteri- nucleatum and VSCs in oral cavity of mothers and um Nucleatum in the pathogenesis in and out the newborns. In: International Conference on Oral mouth. Pril (Makedon Akad Nauk Umet Odd Med Malodour, University of the West of England, 2019. Nauki) 2020; 41: 87-99. 78) Brennan CA, Garrett WS. Fusobacterium nuclea- 92) Fardini Y, Wang X, Témoin S, Nithianantham S, tum - symbiont, opportunist and oncobacterium. Lee D, Shoham M, Han YW. Fusobacterium nu- Nat Rev Microbiol 2019; 17: 156-166. cleatum adhesin FadA binds vascular endothelial 79) Kolenbrander PE, Palmer RJ Jr, Periasamy S, cadherin and alters endothelial integrity. Mol Mi- Jakubovics NS. Oral multispecies biofilm devel- crobiol 2011; 82: 1468-1480. opment and the key role of cell-cell distance. Nat 93) Krisanaprakornkit S, Kimball JR, Weinberg A, Rev Microbiol 2010; 8: 471-480. Darveau RP, Bainbridge BW, Dale BA. Inducible 80) Lancy P Jr, Dirienzo JM, Appelbaum B, Rosan B, expression of human beta-defensin 2 by Fuso- Holt SC. Corncob formation between Fusobacte- bacterium nucleatum in oral epithelial cells: mul- rium nucleatum and Streptococcus sanguis. In- tiple signaling pathways and role of commensal fect Immun 1983; 40: 303-309. bacteria in innate immunity and the epithelial bar- 81) de Andrade KQ, Almeida-da-Silva CLC, Coutin- rier. Infect Immun 2000; 68: 2907-2915. ho-Silva R. Immunological pathways triggered 94) Ahn SH, Chun S, Park C, Lee JH, Lee SW, Lee by Porphyromonas Gingivalis and Fusobacterium TH. Transcriptome profiling analysis of senes- Nucleatum: therapeutic possibilities? Mediators cent gingival fibroblasts in response to Fuso- Inflamm 2019; 2019: 7241312. bacterium nucleatum infection. PLoS One 2017; 82) Guo L, Shokeen B, He X, Shi W, Lux R. Strepto- 12: e0188755. Erratum in: PLoS One 2018; 13: coccus mutans SpaP binds to RadD of Fusobac- e0191209.

4593 A. Dessì, A. Bosco, R. Pintus, G. Orrù, V. Fanos

95) Bhattacharyya S, Ghosh SK, Shokeen B, Eapan verse pregnancy outcomes: consensus report B, Lux R, Kiselar J, Nithianantham S, Young A, of the Joint EFP/AAP Workshop on Periodontitis Pandiyan P, McCormick TS, Weinberg A. FAD-I, and Systemic Diseases. J Periodontol 2013; 84: a Fusobacterium nucleatum cell wall-associat- S164-169. ed diacylated lipoprotein that mediates human 108) Chaim W, Mazor M. Intraamniotic infection with beta defensin 2 induction through Toll-Like Re- fusobacteria. Arch Gynecol Obstet. 1992; 251: ceptor-1/2 (TLR-1/2) and TLR-2/6. Infect Immun 1-7. 2016; 84: 1446-1456. 109) Wahbeh CJ, Hill GB, Eden RD, Gall SA. In- 96) Kolenbrander PE, Andersen RN, Moore LV. Co- tra-amniotic bacterial colonization in premature aggregation of Fusobacterium nucleatum, Sele- labor. Am J Obstet Gynecol 1984; 148: 739-743. nomonas flueggei, Selenomonas infelix, Sele- nomonas noxia, and Selenomonas sputigena 110) Miller JM Jr, Pupkin MJ, Hill GB. Bacterial colo- with strains from 11 genera of oral bacteria. In- nization of amniotic fluid from intact fetal mem- fect Immun 1989; 57: 3194-3203. branes. Am J Obstet Gynecol 1980; 136: 796-804. 97) Socransky SS, Haffajee AD, Cugini MA, Smith 111) Cahill RJ, Tan S, Dougan G, O’Gaora P, Pickard C, Kent RL Jr. Microbial complexes in subgingi- D, Kennea N, Sullivan MH, Feldman RG, Ed- val plaque. J Clin Periodontol 1998; 25: 134-144. wards AD. Universal DNA primers amplify bac- terial DNA from human fetal membranes and 98) Saito A, Kokubu E, Inagaki S, Imamura K, Kita link Fusobacterium nucleatum with prolonged D, Lamont RJ, Ishihara K. Porphyromonas gin- preterm membrane rupture. Mol Hum Reprod givalis entry into gingival epithelial cells modu- 2005; 11: 761-766. lated by Fusobacterium nucleatum is dependent on lipid rafts. Microb Pathog 2012; 53: 234-242. 112) Gonzales-Marin C, Spratt DA, Allaker RP. Ma- ternal oral origin of Fusobacterium nucleatum 99) Metzger Z, Lin YY, Dimeo F, Ambrose WW, in adverse pregnancy outcomes as determined Trope M, Arnold RR. Synergistic pathogenici- using the 16S-23S rRNA gene intergenic tran- ty of Porphyromonas gingivalis and Fusobac- scribed spacer region. J Med Microbiol 2013; terium nucleatum in the mouse subcutaneous 62: 133-144. chamber model. J Endod 2009; 35: 86-94. 113) Doyle RM, Alber DG, Jones HE, Harris K, Fitz- 100) Aral K, Milward MR, Cooper PR. Dysregulation gerald F, Peebles D, Klein N. Term and preterm of inflammasomes in human dental pulp cells labour are associated with distinct microbial exposed to Porphyromonas gingivalis and Fuso- community structures in placental membranes bacterium nucleatum. J Endod 2020; 46: 1265- which are independent of mode of delivery. Pla- 1272. centa 2014; 35: 1099-1101. 101) Jeffcoat MK, Geurs NC, Reddy MS, Cliver SP, 114) Figuero E, Han YW, Furuichi Y. Periodontal dis- Goldenberg RL, Hauth JC. Periodontal infection eases and adverse pregnancy outcomes: mech- and preterm birth: results of a prospective study. anisms. Periodontol 2000 2020; 83: 175-188. J Am Dent Assoc 2001; 132: 875-880. 115) Dixon NG, Ebright D, Defrancesco MA, Hawkins 102) Turton M, Africa CWJ. Further evidence for peri- RE. Orogenital contact: a cause of chorioamnio- odontal disease as a risk indicator for adverse nitis? Obstet Gynecol 1994; 84: 654-655. pregnancy outcomes. Int Dent J 2017; 67: 148- 156. 116) Ebersole JL, Novak MJ, Michalowicz BS, Hodg- es JS, Steffen MJ, Ferguson JE, Diangelis A, 103) Han YW. Can oral bacteria cause pregnancy Buchanan W, Mitchell DA, Papapanou PN. Sys- complications? Womens Health (Lond) 2011; 7: temic immune responses in pregnancy and peri- 401-404. odontitis: relationship to pregnancy outcomes in 104) Jarjoura K, Devine PC, Perez-Delboy A, Herre- the Obstetrics and Periodontal Therapy (OPT) ra-Abreu M, D’Alton M, Papapanou PN. Markers study. J Periodontol 2009; 80: 953-960. of periodontal infection and preterm birth. Am J 117) Wang X, Buhimschi CS, Temoin S, Bhandari V, Obstet Gynecol 2005; 192: 513-519. Han YW, Buhimschi IA. Comparative microbial 105) Chanomethaporn A, Chayasadom A, Wara-As- analysis of paired amniotic fluid and cord blood wapati N, Kongwattanakul K, Suwannarong W, from pregnancies complicated by preterm birth Tangwanichgapong K, Sumanonta G, Matang- and early-onset neonatal sepsis. PLoS One kasombut O, Dasanayake AP, Pitiphat W. Asso- 2013; 8: e56131. ciation between periodontitis and spontaneous 118) Barak S, Oettinger-Barak O, Machtei EE, Spre- abortion: a case-control study. J Periodontol cher H, Ohel G. Evidence of periopathogenic 2019; 90: 381-390. microorganisms in placentas of women with pre- 106) Gauthier S, Tétu A, Himaya E, Morand M, Chan- eclampsia. J Periodontol 2007; 78: 670-676. dad F, Rallu F, Bujold E. The origin of Fusobac- 119) Strauss J, Kaplan GG, Beck PL, Rioux K, Panac- terium nucleatum involved in intra-amniotic in- cione R, Devinney R, Lynch T, Allen-Vercoe E. fection and preterm birth. J Matern Fetal Neo- Invasive potential of gut mucosa-derived Fuso- natal Med 2011; 24: 1329-1332. bacterium nucleatum positively correlates with 107) Sanz M, Kornman K; Working Group 3 of the IBD status of the host. Inflamm Bowel Dis 2011; Joint EFP/AAP Workshop. Periodontitis and ad- 17: 1971-1978.

4594 Fusobacterium nucleatum and alteration of the oral microbiome

120) Tahara T, Shibata T, Kawamura T, Okubo M, odontal pathogens in atherosclerosis: an im- Ichikawa Y, Sumi K, Miyata M, Ishizuka T, Na- munohistologic study. Oral Microbiol Immunol kamura M, Nagasaka M, Nakagawa Y, Ohmi- 2006; 21: 206-211. ya N, Arisawa T, Hirata I. Fusobacterium detect- 131) Figuero E, Sánchez-Beltrán M, Cuesta-Frecho- ed in colonic biopsy and clinicopathological fea- so S, Tejerina JM, del Castro JA, Gutiérrez JM, tures of ulcerative colitis in Japan. Dig Dis Sci Herrera D, Sanz M. Detection of periodontal 2015; 60: 205-210. bacteria in atheromatous plaque by nested poly- 121) Kostic AD, Chun E, Robertson L, Glickman JN, merase chain reaction. J Periodontol 2011; 82: Gallini CA, Michaud M, Clancy TE, Chung DC, 1469-1477. Lochhead P, Hold GL, El-Omar EM, Brenner D, 132) Elkaïm R, Dahan M, Kocgozlu L, Werner S, Fuchs CS, Meyerson M, Garrett WS. Fusobac- Kanter D, Kretz JG, Tenenbaum H. Prevalence terium nucleatum potentiates intestinal tumori- of periodontal pathogens in subgingival lesions, genesis and modulates the tumor-immune mi- atherosclerotic plaques and healthy blood ves- croenvironment. Cell Host Microbe 2013; 14: sels: a preliminary study. J Periodontal Res 207-215. 2008; 43: 224-231. 122) McCoy AN, Araújo-Pérez F, Azcárate-Peril A, 133) Témoin S, Chakaki A, Askari A, El-Halaby A, Yeh JJ, Sandler RS, Keku TO. Fusobacterium Fitzgerald S, Marcus RE, Han YW, Bissada NF. is associated with colorectal adenomas. PLoS Identification of oral bacterial DNA in synovi- One 2013; 8: e53653. al fluid of patients with arthritis with native and 123) Rubinstein MR, Wang X, Liu W, Hao Y, Cai G, failed prosthetic joints. J Clin Rheumatol 2012; Han YW. Fusobacterium nucleatum promotes 18: 117-121. colorectal carcinogenesis by modulating E-cad- 134) Sparks Stein P, Steffen MJ, Smith C, Jicha G, herin/β-catenin signaling via its FadA adhesin. Ebersole JL, Abner E, Dawson D 3rd. Serum Cell Host Microbe 2013; 14: 195-206. antibodies to periodontal pathogens are a risk 124) Flanagan L, Schmid J, Ebert M, Soucek P, factor for Alzheimer’s disease. Alzheimers De- Kunicka T, Liska V, Bruha J, Neary P, De- ment 2012; 8: 196-203. zeeuw N, Tommasino M, Jenab M, Prehn JH, 135) Arane K, Goldman RD. Fusobacterium infec- Hughes DJ. Fusobacterium nucleatum asso- tions in children. Can Fam Physician 2016; 62: ciates with stages of colorectal neoplasia de- 813-814. velopment, and disease out- come. Eur J Clin Microbiol Infect Dis 2014; 33: 136) Pyysalo MJ, Pyysalo LM, Pessi T, Karhunen PJ, 1381-1390. Öhman JE. The connection between ruptured cerebral aneurysms and odontogenic bacteria. 125) Mira-Pascual L, Cabrera-Rubio R, Ocon S, Cos- J Neurol Neurosurg Psychiatry 2013; 84: 1214- tales P, Parra A, Suarez A, Moris F, Rodrigo L, 1218. Mira A, Collado MC. Microbial mucosal colon- ic shifts associated with the development of col- 137) Orrù G, Contu M P, Casula E, Demontis D, orectal cancer reveal the presence of different Blus C, Szmukler-Moncler S, Serreli G, Mase- bacterial and archaeal biomarkers. J Gastroen- rati C, Steri GC, Fanos V, Coghe F, Denott G. terol 2015; 50: 167-179. Periodontal microbiota of Sardinian children: comparing 200-year-old samples to present-day 126) Warren RL, Freeman DJ, Pleasance S, Watson ones. J Pediatr Neonat Individual Med 2017; 6: P, Moore RA, Cochrane K, Allen-Vercoe E, Holt e060123. RA. Co-occurrence of anaerobic bacteria in col- orectal carcinomas. Microbiome 2013; 1: 16. 138) Gil S, Coldwell S, Drury JL, Arroyo F, Phi T, Saa- dat S, Kwong D, Chung WO. Genotype-specif- 127) Swidsinski A, Dörffel Y, Loening-Baucke V, The- ic regulation of oral innate immunity by T2R38 issig F, Rückert JC, Ismail M, Rau WA, Gaschler taste receptor. Mol Immunol 2015; 68: 663-670. D, Weizenegger M, Kühn S, Schilling J, Dörffel WV. Acute appendicitis is characterised by local 139) Sandell MA, Collado M. Genetic variation in the invasion with Fusobacterium nucleatum/necro- TAS2R38 taste receptor contributes to the oral phorum. Gut 2011; 60: 34-40. microbiota in North and South European loca- tions: a pilot study. Genes Nutr 2018; 13: 30. 128) Swidsinski A, Dörffel Y, Loening-Baucke V, Ter- tychnyy A, Biche-Ool S, Stonogin S, Guo Y, Sun 140) Douglas JE, Cohen NA. Taste receptors medi- ND. Mucosal invasion by fusobacteria is a com- ate sinonasal immunity and respiratory disease. mon feature of acute appendicitis in Germany, Int J Mol Sci 2017; 18: 437. Russia, and China. Saudi J Gastroenterol 2012; 141) Xiang Z, Koo H, Chen Q, Zhou X, Liu Y, Si- 18: 55-58. mon-Soro A. Potential implications of SARS- 129) Zhong D, Brower-Sinning R, Firek B, Morowitz CoV-2 oral infection in the host microbiota. J MJ. Acute appendicitis in children is associated Oral Microbiol 2020; 13: 1853451. with an abundance of bacteria from the phylum 142) Scannapieco FA. Role of oral bacteria in respi- Fusobacteria. J Pediatr Surg 2014; 49: 441-446. ratory infection. J Periodontol 1999; 70: 793- 130) Ford PJ, Gemmell E, Chan A, Carter CL, Walk- 802. er PJ, Bird PS, West MJ, Cullinan MP, Seymour 143) Zheng M, Gao Y, Wang G, Song G, Liu S, Sun GJ. Inflammation, heat shock proteins and peri- D, Xu Y, Tian Z. Functional exhaustion of antivi-

4595 A. Dessì, A. Bosco, R. Pintus, G. Orrù, V. Fanos

ral lymphocytes in COVID-19 patients. Cell Mol summary: the relationship between oral health Immunol 2020; 17: 533-535. and pulmonary disease. Br Dent J 2017; 222: 144) Zhou F, Yu T, Du R, Fan G, Liu Y, Liu Z, Xiang 527-533. J, Wang Y, Song B, Gu X, Guan L, Wei Y, Li H, 151) Azarpazhooh A, Leake JL. Systematic review Wu X, Xu J, Tu S, Zhang Y, Chen H, Cao B. Clin- of the association between respiratory diseases ical course and risk factors for mortality of adult and oral health. J Periodontol 2006; 77: 1465- inpatients with COVID-19 in Wuhan, China: a 1482. retrospective cohort study. Lancet 2020; 395: 152) Mori H, Hirasawa H, Oda S, Shiga H, Matsuda 1054-1062. K, Nakamura M. Oral care reduces incidence of 145) Cox MJ, Loman N, Bogaert D, O’Grady J. Co-in- ventilator-associated pneumonia in ICU popula- fections: potentially lethal and unexplored in tions. Intensive Care Med 2006; 32: 230-236. COVID-19. Lancet Microbe 2020; 1: e11. 153) Sjögren P, Nilsson E, Forsell M, Johansson O, 146) Patel J, Sampson V. The role of oral bacteria in Hoogstraate J. A systematic review of the pre- COVID-19. Lancet Microbe 2020; 1: e105. ventive effect of oral hygiene on pneumonia and 147) Chakraborty S. Metagenome of SARS-Cov2 pa- respiratory tract infection in elderly people in tients in Shenzhen with travel to Wuhan shows hospitals and nursing homes: effect estimates a wide range of species - Lautropia, Cutibacte- and methodological quality of randomized con- rium, Haemophilus being most abundant - and trolled trials. J Am Geriatr Soc 2008; 56: 2124- Campylobacter explaining diarrhea. OSF Pre- 2130. prints 2020; published online 24 March. 154) Wolff L, Martiny D, Deyi VYM, Maillart E, Clev- 148) Bao L, Zhang C, Dong J, Zhao L, Li Y, Sun enbergh P, Dauby N. COVID-19-associated fu- J. Oral Microbiome and SARS-CoV-2: beware sobacterium nucleatum bacteremia, Belgium. of lung co-infection. Front Microbiol 2020; 11: Emerg Infect Dis 2020; 27: 975-977. 1840. 155) Hopkins C, Kumar N. Loss of sense of smell as 149) Sampson V, Kamona N, Sampson A. Could marker of COVID-19 infection. ENT UK at The there be a link between oral hygiene and the Royal College of Surgeons of England 2020. severity of SARS-CoV-2 infections? Br Dent J 156) Ralli M, Di Stadio A, Greco A, de Vincentiis M, 2020; 228: 971-975. Polimeni A. Defining the burden of olfactory dys- 150) Manger D, Walshaw M, Fitzgerald R, Doughty J, function in COVID-19 patients. Eur Rev Med Wanyonyi KL, White S, Gallagher JE. Evidence Pharmacol Sci 2020; 24: 3440-3441.

4596