Distribution of Helicobacter Pylori and Periodontopathic Bacterial Species in the Oral Cavity
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biomedicines Article Distribution of Helicobacter pylori and Periodontopathic Bacterial Species in the Oral Cavity 1, 2, 1, , 1 1 Tamami Kadota y, Masakazu Hamada y, Ryota Nomura * y, Yuko Ogaya , Rena Okawa , Narikazu Uzawa 2 and Kazuhiko Nakano 1 1 Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Osaka 565-0871, Japan; [email protected] (T.K.); [email protected] (Y.O.); [email protected] (R.O.); [email protected] (K.N.) 2 Department of Oral and Maxillofacial Surgery II, Osaka University Graduate School of Dentistry, Osaka 565-0871, Japan; [email protected] (M.H.); [email protected] (N.U.) * Correspondence: [email protected] These authors contributed equally to this work. y Received: 14 May 2020; Accepted: 12 June 2020; Published: 15 June 2020 Abstract: The oral cavity may serve as a reservoir of Helicobacter pylori. However, the factors required for H. pylori colonization are unknown. Here, we analyzed the relationship between the presence of H. pylori in the oral cavity and that of major periodontopathic bacterial species. Nested PCR was performed to detect H. pylori and these bacterial species in specimens of saliva, dental plaque, and dental pulp of 39 subjects. H. pylori was detected in seven dental plaque samples (17.9%), two saliva specimens (5.1%), and one dental pulp (2.6%) specimen. The periodontal pockets around the teeth, from which dental plaque specimens were collected, were significantly deeper in H. pylori-positive than H. pylori-negative subjects (p < 0.05). Furthermore, Porphyromonas gingivalis, a major periodontopathic pathogen, was detected at a significantly higher frequency in H. pylori-positive than in H. pylori-negative dental plaque specimens (p < 0.05). The distribution of genes encoding fimbriae (fimA), involved in the periodontal pathogenicity of P. gingivalis, differed between H. pylori-positive and H. pylori-negative subjects. We conclude that H. pylori can be present in the oral cavity along with specific periodontopathic bacterial species, although its interaction with these bacteria is not clear. Keywords: Helicobacter pylori; Porphyromonas gingivalis; periodontopathic bacterial species; molecular biological analysis; oral specimens 1. Introduction Evidence indicates that Helicobacter pylori infects the human organism via the oral cavity and subsequently remains in the gastric tissue for the rest of its host’s life [1]. Chronic inflammation of the gastric mucosa is induced by ammonia and toxins produced by H. pylori [1], eventually causing gastric mucosal damage and diseases such as peptic ulcer and gastric cancer. H. pylori in the oral cavity may cause reinfection of the stomach after eradication therapy [2,3]. However, H. pylori colonizes the oral cavity through an unknown mechanism. Among the more than 700 bacterial species that reside in the human oral cavity [4], some contribute to the progression of periodontal disease. For example, Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia are called the red complex because of their high pathogenicity [5]. The orange complex comprises bacteria such as Prevotella intermedia, Prevotella nigrescens, and Campylobacter rectus, which are associated with periodontal disease, and provides a link between pathogenic species such as the red complex and commensal bacteria [5]. Furthermore, commensal bacteria known as Biomedicines 2020, 8, 161; doi:10.3390/biomedicines8060161 www.mdpi.com/journal/biomedicines Biomedicines 2020, 8, 161 2 of 14 early colonizers with low pathogenicity include species in the green and yellow complexes, such as Capnocytophaga ochracea, Capnocytophaga sputigena, and Eikenella corrodens. These latter species are not directly involved in the development of periodontal disease, although they are involved in the establishment of the red and orange complexes [5]. A large number of studies have shown that periodontal bacteria are associated with various systemic diseases, such as diabetes, cardiovascular disease, aspiration pneumonia, preterm birth, low birth weight, and Alzheimer0s disease [6]. Recent studies have shown differences in the oral microbiota between cancer patients and healthy subjects [7], and that specific oral microbiota may be involved in the development of cancers other than in the head and neck region. Alterations in the oral microbiota tend to be remarkable in cancer patients, especially in gastrointestinal tumor patients [7], and some epidemiological studies have pointed to a relationship between periodontal disease and the risk of gastric cancer [7]. Nevertheless, few studies have focused on the relationship between the presence H. pylori in the oral cavity and that of periodontopathic bacterial species [8]. The presence of small numbers of the keystone pathogen P. gingivalis significantly influences the development of periodontal disease [9]. An important pathogenic factor of P. gingivalis is an approximately 41 kDa filamentous appendage (FimA), encoded by the genes fimA, which is expressed on the cell surface. The fimA genes are classified as genotypes I to V and Ib [10]. The fimA genotypes I, III, and V are mainly detected in healthy gingival tissue, whereas types II, IV, and Ib are mainly detected in periodontal tissues of patients with periodontitis [10]. The detection of H. pylori in the oral cavity, which is widely performed using PCR, ranges from 0% to 100% [11]. These results indicate that it is difficult to detect H. pylori in the oral cavity with high sensitivity and specificity, because many bacterial species are present. To overcome this problem, we synthesized novel PCR primer sets using the consensus sequences of the genes of 50 strains of H. pylori [12]. Nested PCR analyses using these primers detect at least 1 to 10 H. pylori cells in the oral cavity [13]. Furthermore, closely related H. pylori species are not detected using this method [13]. We found that this novel nested PCR method detects H. pylori in samples of oral cavity tissues acquired from subjects of all ages [12–16]. Periodontal disease is associated with the colonization of the oral cavity by H. pylori [17,18]. However, most studies have focused on clinical periodontal conditions, whereas there are few studies considering the distribution of periodontopathic bacterial species. Here, we examined oral cavity specimens to analyze the association between H. pylori and periodontal disease, focusing on major periodontopathic bacterial species. 2. Materials and Methods 2.1. Ethics Statement This study was conducted in compliance with the Declaration of Helsinki. The Ethics Committee of Osaka University Graduate School of Dentistry approved this study (Approval number: H30-E32, 4 December 2018). Before specimen collection, all subjects provided written informed consent. 2.2. Subjects The subjects (13 males and 26 females; age range, 16–70 years; median age, 31 years; mean age, 35.3 15.1 years) were referred to the Department of Oral and Maxillofacial Surgery at Osaka ± University Dental Hospital from January 2019 to February 2020 because of problems requiring tooth extraction of the third molar, such as dental caries and pericoronitis. Sixteen of 39 extracted teeth were impacted. Patients’ characteristics were as follows: history of systemic and gastrointestinal diseases, prior H. pylori infection of gastric tissue, and prior eradication of H. pylori from gastric tissue. The presence or absence of dental caries in the extracted tooth was diagnosed by visual inspection, palpation with a dental explorer, and X-ray examination. The depth of the periodontal pocket (also called probing depth) was measured from the gingival margin to the bottom of the pocket using a dental Biomedicines 2020, 8, 161 3 of 14 probe. The deepest level reached was recorded. Extraction of the third molar, medical examination by an interview, and measurement of the depth of the periodontal pockets were performed by a single doctor in the department of oral and maxillofacial surgery, and dental caries diagnosis was performed by a single dentist in the department of pediatric dentistry. 2.3. Oral Cavity Specimens The extracted third molar was placed in a sterile plastic tube containing 2.5 mL of sterile saline, and sonication was used to separate the dental plaque from the tooth. After the tooth was removed, the suspension was centrifuged, and the supernatant was discarded. The resulting suspension served as a dental plaque specimen from the extracted tooth. Next, the pulp chamber of the extracted tooth was opened using a sterilized dental handpiece and diamond point, and the dental pulp specimen was deposited into a sterile plastic tube containing 1 mL of sterile saline, according to a published method [12]. Saliva (1 mL) from each subject was collected into a sterile disposable tube. The dental pulp and saliva specimens were centrifuged, and the supernatant was discarded. Bacterial DNA was extracted from these specimens of dental plaque, dental pulp, and saliva as described below. 2.4. H. pylori Strains and Growth Condition H. pylori reference strain J99 (ATCC 700824) purchased from Summit Pharmaceuticals International corporation (Tokyo, Japan) served as the positive control. Blood agar plates (Becton Dickinson, Franklin Lakes, NJ, USA), incubated at 37 ◦C for 3–5 days, were used to isolate bacterial colonies [12]. Thereafter, colonies were inoculated into 10 mL of brucella broth (Becton Dickinson) supplemented with 1 mL of horse serum by using a sterilized platinum loop and then incubated at 37 ◦C for 24 h under microaerophilic conditions. The bacteria were collected using centrifugation at 8000 rpm for 10 min, and genomic DNA was extracted as described below. 2.5. Bacterial DNA Extraction Bacterial DNA was extracted using a published method [12]. Briefly, oral specimens or H. pylori strain J99 were resuspended in 250 µL of 10 mM Tris-HCl (pH 8.0) containing 100 mM NaCl and 1 mM EDTA. The cells were collected using centrifugation, lysed in 600 µL of Cell Lysis Solution (Qiagen, Düsseldorf, Germany), and incubated at 80 ◦C for 5 min, followed by the addition of 3 µL of RNase A (10 mg/mL; Qiagen) and incubation at 37 ◦C for 30 min.