Fifty strains of Rothia dentocariosa Georg and Brown were characterized morphologically, biochemically, and serologically. All strains had characteristics agreeing with previous morphological descriptions of this organism, although there was greater biochemical and serological strain variation than previously reported. Four biotypes were established on the basis of variability in reduction of nitrite, production of urease, hydrolysis of esculin, and formation of acid from lactose, mannitol, mannose, raffinose, rhamnose, salicin, and trehalose. Three serotypes and a group of fluorescent antibody-negative strains were identified on the basis of the fluorescent antibody technique. A relationship between the four biotypes and the three serotypes was established.The monospecific genus Rothia, with type species Rothia dentocariosa, was proposed by Georg and Brown (2) t o accommodate microorganisms previously designated as Actinomyces dentocariosus, Nocardia dentocariosus, and Nocardia salivae. Brown, Georg, and Waters (1) subsequently studied 50 isolates having the morphological and biochemical characteristics of Rothia. Hammond (3) showed that all of his strains of R . dentocariosa contained a soluble polysaccharide antigen (RPS), and the detection of this antigen by the fluorescent-antibody (FA) technique is useful in identifying this organism.Rothia is included in the family Actinomycetaceae because of its branching, filamentous morphology and its ability to septate into bacillary, diphtheroidal, or coccal cells, or a mixture of these; its colonial morphology, including spider microcolonies and mature colonies which may be heaped and rough or entirely smooth; and its cell wall composition. However, Rothia differs from the genera A ctinom y ces, A rachnia, Bifido bacterium, and Bacterionema in its aerobic tendencies, its production of catalase, its lack of growth stimulation by COZY and its production of lactose as the major end product from glucose fermentation.Among the organisms isolated from dental calculus in this laboratory were a number of filamentous, aerobic, gram-p ositive, catalasepositive strains resembling R o thia morphologically but possessing variant biochemical reactions and not reacting with antisera By comparing the morphological, biochemical, and serological characteristics of R othia with Rothia-like organisms, we hope t o clarify the uncertain status of the latter. MATERIALS AND METHODSBacterial strains. The sources and designations of the fifty strains used in this study are given in Table 1.All cultures were maintained by monthly transfer on trypiic soy agar (TSA) (Difco) slants. Prior to use, the cultures were transferred twice in tryptic soy broth (TSB) (Difco).Colonial morphology. TSB cultures were streaked onto two TSA plates and incubated aerobically and anaerobically at 37 C. The anaerobic plate was incubated in a Torbal jar containing N,:H,:CO, (80:20: 10). Microcolonies were observed after 18 and 24 h of incubation at a magnification of X l O O to X400. Mature colonies were observed a...

Species-specific FITC conjugated antiserum can be prepared for each of the five species of Actinomyces and for Arachnia propionica. These serums can be used for rapid and specific identification of pure or mixed cultures of the bacteria and for identification of organisms seen in direct smears of clinical material or in tissue sections. Two serotypes each of A bovis, A odontolyticus, A israelii, A viscosus, and A propionica have been established, and A naeslundii has been tentatively divided into four serotypes.

A comparative study of 64 strains of Actinomyces israelii was done with the use of techniques standardized by the Subgroup on Taxonomy of the Microaerophilic Actinomycetes. Emphasis was placed on the range of variation to assist recognition of clinical isolates and aid in differentiation from Actinomyces-like organisms. None of the strains was positive for catalase or indole, or in the Voges-Proskauer test; 90% were methyl red-positive and 62% were nitrate-positive. Acid was produced from: glucose (100%), xylose (100%), salicin (98%), raffinose (95%), lactose (89%), cellobiose (83%), mannose (78%), arabinose (76%), inositol (58%), mannitol (48%), starch (31 %), glycogen (0%), glycerol (O%), and rhamnose (0%). A. israeli can be identified by the fluorescent-antibody method, but there is no single morphological or biochemical characteristic which can be used for its identification. By both fluorescent-antibody and gel-diffusion techniques, the serological classification of A. israelii group D with serotypes 1 and 2 was verified. Eleven serotype 2 strains were compared morphologically, biochemically, and serologically with 53 serotype 1 strains. All but two of the serotype 2 strains produced viscous growth in broth and none fermented arabinose. tests. 873

Sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis was used to compare soluble protein fractions from 36 strains of Rothia dentocariosa and related bacteria. The resulting protein patterns were examined to identify the bands of major and minor frequency within the genus. A cluster analysis revealed three major Rothia groups and a fourth group representing the genus Actinornyces. Our data demonstrated good correlations (>70%) with existing biotyping and serotyping schemes of these isolates. We suggest that electrophoretic group 2 represents a new Rothia species.