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REVIEW 10.1111/j.1469-0691.2004.00784.x

Rothia dentocariosa: and differential diagnosis A. von Graevenitz

Gloriastrasse 32, Zu¨ rich, Switzerland

ABSTRACT As recent external quality control results have shown, the diagnosis of dentocariosa infection still presents problems for clinical laboratories. This review describes the taxonomy, as well as the chemotaxonomic, morphological and biochemical characteristics, of this organism, and surveys that may be confused with . Keywords Identification, Rothia dentocariosa, taxonomy Accepted: 25 March 2003 Clin Microbiol Infect 2004; 10: 399–402

lum and ⁄ or the catalase test may not have INTRODUCTION been correct in individual cases. Thus, it was In 2001, the Swiss External Quality Assessment obvious that R. dentocariosa was also a problem Scheme in Bacteriology and Mycology, which organism. operates under the direction of the author [1], sent These observed difficulties were surprising in out a strain of Rothia dentocariosa to 50 laboratories view of the fact that R. dentocariosa has been participating in the scheme. The organism was known for over 35 years. In 1967, Georg and described as a bacterium isolated from a case of Brown proposed the genus Rothia [4] for a group vertebral osteomyelitis, similar to a case reported of coccoid to diphtheroid to filamentous Gram- in the literature [2]. Only 36 (72%) of the partic- positive organisms isolated from the human oral ipants arrived at a correct diagnosis, mostly by cavity, naming the genus after Roth [5], who had use of the API Coryne system, v.2 (bioMe´rieux, La performed basic studies on organisms, isolated Balme-les-Grottes, France). This score was below from carious lesions, that had been described the average for the yearly performance of all the initially by Onisi [6] as dentocariosus. participating laboratories [3], and was similar to Subsequently, similar organisms were isolated in scores obtained for ‘problem organisms’ such as several laboratories from a variety of human Lactobacillus spp., Clostridium tertium, Neisseria sources, mostly from the oral cavity, but also weaveri, Capnocytophaga spp., Eikenella corrodens from blood, respiratory secretions, abscesses, and Moraxella spp. [1,3]. Five participants would wounds, peritoneal dialysates and the eye [7,8]. have sent the strain to a reference laboratory; four Reports of human disease caused by R. dentocar- participants identified it as a species of coagulase- iosa started to be published in the late 1970s [9], negative staphylococci by means of the API Staph and at least 30 case reports can now be found in or ID32 Staph systems; three participants identi- the literature, many of which describe patients fied it as Stomatococcus mucilaginosus (which is an with endocarditis. These reports have been organism now classified as ) reviewed recently [10,11], and interested readers with ID32 Staph; and three participants identified are referred to these previous reviews for further it, respectively, as Propionibacterium spp., Acti- details. nomyces spp. and Rhodococcus equi by means of API Coryne; however, incubation times, inocu- TAXONOMY The taxonomic position of the genus Rothia has Corresponding author and reprint requests: A. von Graeve- nitz, Gloriastrasse 32, CH 8028 Zu¨ rich, Switzerland undergone a number of changes since Georg and E-mail: [email protected] Brown first assigned it to the family Actinomy-

2004 Copyright by the European Society of Clinical Microbiology and Infectious Diseases 400 Clinical Microbiology and Infection, Volume 10 Number 5, May 2004 cetaceae and proposed R. dentocariosa as the type Microscopically, the morphology varies from (and only) species [4]. Possible assignments to the coccoid to diphtheroid (with clavate ends) to genera Actinomyces and were rejected on filamentous. Coccoid forms are observed chemotaxonomic, metabolic and biochemical predominantly in fluid cultures, and filamentous grounds. More recent molecular studies [12] forms on plates, but mixtures may appear in any placed the genus in the family , culture. Rudimentary branching and loss of the suborder Micrococcineae, order Actinomycetales, Gram-positive appearance may be seen in ageing subclass Actinobacteridae, class . It cultures. Cells occur singly, in pairs, in clusters or is thus in the same family as the genera Micrococ- in chains, and colonial pleomorphism can also be cus, Arthrobacter, Kocuria, Nesterenkonia, Renibacte- observed [7,8]. rium and Stomatococcus, all of which show R. dentocariosa grows faster under aerobic than characteristic signature nucleotides in their 16S under anaerobic conditions, and does not need rDNA sequences [12]. Subsequently, S. mucilagi- CO2 or lipids for growth. On non-selective media nosus, the only species in the genus Stomatococcus, used in the clinical laboratory, the organism will was reclassified as Rothia mucilaginosa on the basis grow within 24 h to form colonies of 1-mm of 16S rRNA gene sequences and whole-cell diameter, which will enlarge to 2–3 mm within protein patterns [13]. 48 h. There is no growth on Sabouraud dextrose Heterogeneity within R. dentocariosa has been agar [6]. In contrast to other diphtheroid organ- observed, initially by biotyping and serotyping isms, fosfomycin may be inhibitory to R. dento- [8], and later by pyrolysis mass spectrometry [14], cariosa [20]. Colonies are either of a smooth, whole-cell protein analysis and 16S rRNA gene convex type with entire edges, or of a rough form sequencing [15]. The latter observation led to the which shows either a convoluted, cerebriform or elaboration of two genomovars, which, however, ‘spoke-wheel’ surface with irregular or scalloped cannot be distinguished phenotypically and do edges, or a pebbly surface [7]. Colonies may not coincide with biotypes [15] (K. Bernard, adhere to the agar surface. Mixtures of colony personal communication). types also occur. Under anaerobic conditions, Finally, an animal species, Rothia nasimurium, small ‘spider’ colonies with filamentous borders from the nose of a mouse [13], and an environ- are the most common form. mental species, Rothia amarae, from sludge [16], Table 1 summarises the biochemical reactions both distinct phenotypically from R. dentocariosa, of R. dentocariosa. Of note is the recent discovery have been described recently. of urease-positive and catalase-negative strains [15,20] (K. Bernard, personal communication). CHARACTERISTICS OF R. DENTOCARIOSA Table 1. Biochemical reactions of Rothia dentocariosa [7–9,15,20,30,31] R. dentocariosa is a Gram-positive, non-acid-fast, non-spore-forming, non-pigmented, non-haemo- 100% Positive > 90% Positive > 90% Negative 100% Negative lytic, non-motile bacterium. Chemotaxonomical- Kligler’s agara Triple sugar iron agara ly, it is characterised by a guanine-to-cytosine K ⁄ A, H2S-negative K ⁄ A, H2S-negative DNA ratio of 47–53 mol%. The main cellular Fermentation:b Fermentation: Fermentation: Fermentation: Fructose Ribose Lactose Arabinose fatty acids are C15:0 ai, C17:0 ai, C16:0 i and Glucose Salicin Mannitol Cellobiose Maltose Trehalose Raffinose Glycogen C16:0. The peptidoglycan is of the A3a type; that Sucrose Rhamnose Inositol is, DD-alanine is found in position 4, LL-lysine is Mannose Starch found in position 3, and the inter-peptide bridge Xylose a c b c LL -Glucuronidase -Glucuronidase consists of -alanine. The polar lipids are di- and Pyrazinamidasec mono-phosphatidylglycerol, and the menaqui- Catalase Urease Indole DNase Oxidase nones are unsaturated with seven isoprene units. Aesculin hydrolysis Lysine The cell-wall sugars are galactose, fructose, decarboxylase Nitrate to nitrite Ornithine, glucose and ribose [17–19]. The bacterium is decarboxylase fermentative, with the main end-products of CAMP test carbohydrate metabolism being lactic and acetic aA, acid (without gas); K, alkaline. bWithout gas. acids. cAPI ZYM system.

2004 Copyright by the European Society of Clinical Microbiology and Infectious Diseases, CMI, 10, 399–402 von Graevenitz Rothia dentocariosa 401

R. dentocariosa, by end-product analysis (succinate IDENTIFICATION OF in Actinomyces and Arcanobacterium, propionate in R. DENTOCARIOSA IN THE Propionibacterium, and lactate in Listeria), and by CLINICAL LABORATORY CAMP tests. Aesculin- or nitrate-negative strains, Identification of R. dentocariosa in the clinical as well as urease-positive strains, may suggest laboratory starts with the observation of colonial Corynebacterium freneyi, Corynebacterium sundsval- and microscopic features. Biochemical testing lense or Dermabacter hominis. Again, observation of should follow [21] (Table 1). As a minimum, morphology and enzymatic reactions (e.g., ornith- fermentation of glucose, sucrose, maltose, mann- ine and lysine decarboxylase, pyrazinamidase) itol and xylose should be tested, together with should lead to the correct identification [28–31]. nitrate reduction, urease production, aesculin Only in exceptional circumstances should 16S hydrolysis, catalase and motility. Kligler’s or rDNA sequencing or cellular fatty-acid analysis triple sugar iron agar should also be inoculated. be necessary to identify a clinical isolate. The In lieu of single tests, commercial identification presence of > 5% C18:1 omega c9 or C15:0 i will systems such as API Coryne v.2 [22] or RapID CB rule out R. dentocariosa [32]. Plus (Remel Inc., Norcross, GA, USA) [23] may be used; both contain R. dentocariosa in their data REFERENCES bases. Directions for use must be followed strictly. Misdiagnoses will ensue if identification systems 1. Siegrist HH, Pu¨nter-Streit V, von Graevenitz A. The Swiss for anaerobes are used [24]. External Quality Assessment Scheme in Bacteriology and Colonial morphology alone can rule out Nocar- Mycology, 1992–1996. Accred Qual Assur 1998; 3: 203–207. 2. Llopis F, Carratala J. Vertebral osteomyelitis complicating dia spp. because nocardiae grow more slowly, Rothia dentocariosa endocarditis. 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