Minimal inhibitory concentrations of various antimicrobial agents for human oral anaerobic bacteria

The minimal inhibitory concentrations of a series of antimicrobial agents for human oral organisms were determined under anaerobic growth conditions by an agar dilution assay. With the exception of black-pigmented Bacteroides spp., minimal inhibitory concentrations for oral isolates were similar to those for non-oral isolates of organisms of the same or closely related species.

Bacterial IgG and IgM antibody titers in acute necrotizing ulcerative gingivitis

IgG AND IgM ANTIBODY TITERS to eight bacterial isolates were measured by indirect immunofluorescence and ELISA in sera from acute necrotizing ulcerative gingivitis (ANUG) patients during the acute phase, from ANUG patients during the convalescent phase, from patients with gingivitis and from subjects with normal gingiva. Subjects were matched with respect to age and sex. Compared to the gingivitis and healthy groups, the ANUG groups exhibited significantly higher IgG and IgM titers to intermediate-sized spirochetes and higher IgG titers to Bacteroides melaninogenicus subsp intermedius. The findings support recent studies showing that these organisms are major bacterial components in ANUG lesions. They also suggest that these bacteria proliferate above-normal levels several weeks or months prior to the clinical onset of ANUG.

Serology of oral Actinobacillus actinomycetemcomitans and serotype distribution in human periodontal disease

Actinobacillus actinomycetemcomitans from the human oral cavity was serologically characterized with rabbit antisera to the type strain NCTC 9710; a number of reference strains, including Y4, ATCC 29522, ATCC 29523, ATCC 29524, NCTC 9709; and our own isolates representative of each of 10 biotypes. Using immunoabsorbed antisera, we identified three distinct serotypes by immunodiffusion and indirect immunofluorescence. Serotype a was represented by ATCC 29523 and SUNYaB 75; serotype b was represented by ATCC 29522 and Y4; and serotype c was represented by NCTC 9710 and SUNYaB 67. Indirect immunofluorescence revealed no reaction between the three A. actinomycetemcomitans serotype-specific antisera and 62 strains representing 23 major oral bacterial species. Distinct from the serotype antigens were at least one A. actinomycetemcomitans species common antigen and an antigen shared with other Actinobacillus species, Haemophilus aphrophilus, and Haemophilus paraphrophilus. All serotype a A. actinomycetemcomitans strains failed to ferment xylose, whereas all serotype b organisms fermented xylose. Serotype c included xylose-positive as well as xylose-negative strains. A total of 301 isolates of A. actinomycetemcomitans from the oral cavity of 74 subjects were serologically categorized by indirect immunofluorescence with serotype-specific rabbit antisera. Each patient harbored only one serotype of A. actinomycetemcomitans. Fourteen healthy subjects, five diabetics, and seventeen adult periodontitis patients exhibited serotypes a and b in approximately equal frequency, whereas serotype c was found less frequently. In contrast, in 29 localized juvenile periodontitis patients, the incidence of serotype b was approximately two times higher than that of serotypes a or c, suggesting a particularly high periodontopathic potential of A. actinomycetemcomitans serotype b strains. In subjects infected with A. actinomycetemcomitans, serum antibodies were detected to the serotype antigens, indicating that these antigens may play a role in the pathogenesis of periodontal disease.

The periodontal microflora of juvenile diabetics. Culture, immunofluorescence, and serum antibody studies

These studies demonstrate a unique constellation of organisms populating the subgingival area in periodontitis lesions of patients with juvenile or insulin-dependent diabetes mellitus (IDDM). The cultivable microflora was predominated by Capnocytophaga and anaerobic vibrios in the patients studied. In some patients, Actinobacillus actinomycetemcomitans were also found. This distinguishes the subgingival flora of IDDM patients suffering from periodontitis from that of patients with localized juvenile periodontitis (LJP), and that of adult periodontitis patients. In LJP most patients harbor both A actinomycetemcomitans and Capnocytophaga subgingivally; and in periodontitis lesions from nondiabetic adults, black-pigmented Bacteroides such as B gingivalis or B melaninogenicus subspecies intermedius are often found. Antibiotic susceptibility patterns suggest that penicillin or tetracycline or its analogs such as minocycline may be effective against the predominant cultivable microflora in periodontal lesions of IDDM patients; however, individual patients may harbor flora with significant resistance to these antibiotics.

Relationships among the oral fusobacteria assessed by DNA-DNA hybridization

DNA was purified from 16 strains of Fusobacterium nucleatum and from five strains representing other Fusobacterium species. The relationships among fusobacteria were examined by DNA-DNA hybridization and by determining the guanine plus cytosine content of the DNA. F. nucleatum was found to comprise a heterogenous group of organisms related to Fusobacterium periodonticum and Fusobacterium simiae, but unrelated to any of the other species of Fusobacterium tested.

Suppression of penicillin-resistant oral Actinobacillus actinomycetemcomitans with tetracycline. Considerations in endocarditis prophylaxis

Actinobacillus actinomycetemcomitans is an oral bacterium which is being encountered with increasing frequency in infective endocarditis. This organism occurs in high numbers in periodontitis lesions of patients with localized juvenile periodontitis (periodontosis). It is present infrequently, and only in low numbers in most other individuals. Its common resistance to penicillin, erythromycin and vancomycin represents a clinical problem in patients at risk of developing endocarditis after dental treatment. However, the high activity of tetracyclines against A. actinomycetemcomitans may be useful in prophylactic endocarditis considerations by allowing a suppression of the organism prior to the institution of recommended prophylactic protocols. In this study, we determined the effect of systemic tetracycline-HCl therapy (1 gm/day) on the oral A. actinomycetemcomitans population in five localized juvenile periodontitis patients who were heavily infected with the organism. A. actinomycetemcomitans could not be detected in samples of subgingival and supragingival dental plaque and cheek mucosal surfaces following 14 days of administration of systemic tetracycline. The organism was still undetectable 3 weeks after therapy but it reappeared at a few oral sites at week 8 post-treatment. On the basis of this data, it is proposed that the prophylactic endocarditis therapy of patients with high numbers of penicillin-resistant A. actinomycetemcomitans include a two-stage approach: first, the systemic administration of tetracycline for 14 days, and second, institution of a conventional prophylactic protocol during the time of dental treatment.

Studies of leukotoxin from Actinobacillus actinomycetemcomitans using the promyelocytic HL-60 cell line

The promyelocytic HL-60 cell line was examined for susceptibility to leukotoxin from Actinobacillus actinomycetemcomitans. Strains of A. actinomycetemcomitans which caused lysis of human peripheral blood polymorphonuclear leukocytes also lysed HL-60 cells as determined by release of intracellular lactate dehydrogenase. The killing of HL-60 cells by A. actinomycetemcomitans was dose dependent and temperature dependent, reached maximal levels after 45 min of incubation, and was inhibited by rabbit antisera to A. actinomycetemcomitans. Of 100 oral isolates of A. actinomycetemcomitans from 55 subjects, 16% from 11 healthy subjects, 43% from 13 adult periodontitis patients, 75% from 4 insulin-dependent diabetics, 66% from 2 generalized juvenile periodontitis patients, and 55% from 25 localized juvenile periodontitis patients produced leukotoxin. The same subject could harbor both leukotoxin-producing and -nonproducing isolates. The significantly higher proportion of leukotoxin-producing isolates in the disease groups compared with the healthy group is consistent with the hypothesis that leukotoxin from A. actinomycetemcomitans is an important virulence factor in the pathogenesis of certain forms of periodontal disease.

Bacterial antibody titers in ligature-induced periodontitis in beagle dogs

Serum antibodies to indigenous bacteria in ten beagle dogs were examined over a 7-month period during the development of ligature-induced periodontitis. Gram-negative strains comprised approximately 75% of the cultivable periodontitis microflora with a predominance of black-pigmented Bacteroides species. A total of 44 bacterial strains representing the predominant cultivable subgingival beagle dog microflora was selected for antibody determination. The IgG and, in some cases, IgM serum antibody titers to these organisms were determined by indirect immunofluorescence. The antibody titers to most test strains remained unchanged during the experimental period. Gram-negative bacteria generally exhibited lower titers than the Gram-positive bacteria. Especially low titers were found for the black-pigmented Bacteroides. Four dogs that developed the most severe periodontitis showed about 2-fold higher IgG titers to some Gram-negative anaerobic rods in the pre-ligation period than dogs that developed a more moderate periodontitis. These data suggested a possible diagnostic value of such antibody determinations. However, the overall finding of the present study was that serum antibody titers to key periodontopathic organisms remained low throughout the experiment. This result may suggest that the rapid periodontal destruction in ligature-induced periodontitis is due in part to an inadequate antibody response against the infecting microorganisms and their pathogenic products.

Selective recovery of oral Capnocytophaga spp. with sheep blood agar containing bacitracin and polymyxin B

On the basis of in vitro susceptibility testing of antibiotics, dyes, and other antimicrobial agents, we developed and evaluated a medium, TBBP, for the selective isolation of oral Capnocytophaga spp. TBBP medium consists of 4% Trypticase soy agar (BBL Microbiology Systems, Cockeysville, Md.), 5% sheep blood, 0.1% yeast extract, 50 micrograms of bacitracin per ml, and 100 micrograms of polymyxin B per ml. A total of 34 Capnocytophaga stock cultures grew well on TBBP medium. Except for some streptococcal strains, TBBP medium inhibited growth of all test stock culture isolates of common oral gram-positive and gram-negative species. In a clinical study of 15 deep periodontal pockets, TBBP medium demonstrated Capnocytophaga recoverability that was similar to or higher than that shown by a nonselective blood agar medium. Typical Capnocytophaga colonial morphology enabled us to readily distinguish this organism from the few other bacteria which could grow on TBBP medium.

Long-wave UV light fluorescence for identification of black-pigmented Bacteroides spp

Black-pigmented Bacteroides strains were grown on blood agar, and the colonies were evaluated for fluorescence from long-wave UV light. Most test strains of Bacteroides melaninogenicus subsp. intermedius exhibited a brilliant red fluorescence. B. melaninogenicus subsp. melaninogenicus fluoresced mostly red-orange. Bacteroides asaccharolyticus showed a yellow or red fluorescence. The intensity of the Bacteroides fluorescence weakened when the black pigment of the colonies developed. In contrast, neither young nor old colonies of the oral species Bacteroides gingivalis displayed fluorescence. Since B. gingivalis can produce severe oral infections and also can seed to nonoral sites, awareness of the inability of this organism to fluoresce is important for microbiologists utilizing UV light fluorescence to screen for black-pigmented Bacteroides spp. The present data also indicate that UV light fluorescence may be a rapid method of distinguishing some black-pigmented Bacteroides spp.

The effect of short-term administration of minocycline HCl on gingival inflammation and subgingival microflora

The purpose of this investigation was to determine the efficacy of minocycline hydrochloride in the management of subgingival microorganisms and periodontal disease. In a double-blind, split-mouth study, minocycline or placebo was administered systemically for 7 days to 26 adults with moderate-to-serve periodontitis. Four study groups were examined: (i) minocycline-scaled, (ii) minocycline-unscaled, (iii) placebo-scaled, and (iv) placebo-unscaled. The minocycline-scaled group responded most favorably, with improved gingival health for at least 49 days and with marked reductions in total bacterial counts and proportions of spirochetes for at least 70 days (termination of the study). Minocycline administration with no periodontal scaling and root planing also resulted major, long-lasting shifts in the subgingival microflora. Scaling alone was least effective in changing the microflora. The data indicated that minocycline may be a useful adjunct in the treatment of periodontal disease. Further studies are needed, however, to determine the long-term effect of minocycline therapy on the periodontal attachment level.

Inhibition of neutrophil chemotaxis by soluble bacterial products

BACTERIAL-NEUTROPHIL INTERACTIONS may be critical determinants of virulence in periodontal diseases. This study was undertaken to examine the ability of major bacterial species from the human oral cavity to inhibit (1) peripheral blood neutrophil chemotaxis, (2) chemotactic formylmethionyl peptide binding, and (3) phagocytosis. Included were cultured supernatants and sonic extracts obtained from strains of Capnocytophaga, Bacteroides gingivalis, Fusobacterium nucleatum, Bacteroides asaccharolyticus, Capnocytophaga species, Actinobacillus actinomycetemcomitans, Neisseria, Actinomyces viscosus, Bacterionema matruchotii, Streptococcus mitis, Streptococcus mutans, and Streptococcus sanguis. Chemotaxis was measured using Boyden chambers; phagocytosis was determined using Staphylococcus aureus as the indicator organism and radioactive chemotactic peptide binding was assessed by a rapid filtration assay. None of the test organisms were cytotoxic to neutrophils or inhibited neutrophil phagocytosis. Capnocytophaga species., Bacteroides species., A. actinomycetemcomitans, and F. nucleatum produced factors which specifically inhibited neutrophil chemotaxis. Activity was lost after dialysis. Extracts of Bacteroides species, A. actinomycetemcomitans and F. nucleatum, which were not chemotactic by themselves, inhibited binding of chemotactic peptide suggesting that in vitro chemotaxis inhibition was mediated by nonchemotactic components that compete for the chemotactic factor receptor on the neutrophil. The exception was Capnocytophaga which appeared to inhibit chemotaxis by inhibition of a post-binding event. Such chemotactic inhibitors from periodontopathic organisms that inhibit neutrophil function may be important determinants of virulence.

Selective medium for isolation of Actinobacillus actinomycetemcomitans

A selective medium, TSBV (tryptic soy-serum-bacitracin-vancomycin) agar, was developed for the isolation of Actinobacillus actinomycetemcomitans, TSBV agar contained (per liter) 40 g of tryptic soy agar, 1 g of yeast extract, 100 ml of horse serum. 75 mg of bacitracin, and 5 mg of vancomycin. The TSBV medium suppressed most oral species and permitted significantly higher recovery of A. actinomycetemcomitans than nonselective blood agar medium. The distinct colonial morphology and positive catalase reaction of A. actinomycetemcomitans easily distinguished this bacterium from Haemophilus aphrophilus, Capnocytophaga species, and a few other contaminating organisms. With the TSBV medium, even modestly equipped laboratories will be able to isolate and identify A. actinomycetemcomitans from clinical specimens.

Salient Biochemical Characters of Actinobacillus actinomycetemcomitans

A total of 136 strains of Actinobacillus actinomycetemcomitans were studied for 135 features. All isolates were small nonmotile capnophilic gram-negative rods which grew with no requirement of X or V growth factors. They all decomposed hydrogen peroxide, were oxidase-negative and benzidine-positive, reduced nitrate, produced strong alkaline and acid phosphatases, and fermented fructose, glucose and mannose. Variable fermentation results were obtained with dextrin, maltose, mannitol and xylose. Some isolates produced small amounts of gas. Representative strains of Haemophilus aphrophilus were morphologically and biochemically quite similar to A. actinomycetemcomitans. Characters which should prove to be useful to identify and distinguish these two species include catalase reaction. fermentation of lactose, starch, sucrose and trehalose, and resistance to sodium fluoride. This information allows a rapid diagnosis by species and may be helpful in studies of infections involving these organisms.

Beta-lactamase producing bacteria in the human oral cavity

Twenty-six individuals who had no history of long-term antibiotic therapy were examined for the prevalence of beta-lactamase producing bacteria in the oral cavity. Samples from a total of 159 normal and diseased periodontal sites, 44 cheek mucosae, 22 tongue dorsa and 22 salivas were studied. Penicillin resistant organisms were recovered from Trypticase soy blood agar plates containing 1.3 microgram/ml or 2 microgram/ml Benzylpenicillin. Beta-lactamase formation by these isolates was determined using a micro-iodometric assay. Low levels of penicillin resistant organisms were found in all samples. Approximately 10% of the samples yielded Beta-lactamase producing strains. Except for a few Veillonella parvula strains, all Beta-lactamase forming isolates were members of the Bacteroides melaninogenicus subspecies melaninogenicus - Bacteroides oralis group of organisms. These species can produce severe infections and, therefore, the present findings may be important in the clinical management of oral and nonoral infection.

Cellular fatty acid and soluble protein composition of Actinobacillus actinomycetemcomitans and related organisms

The cellular fatty acid and protein content of twenty-five representative strains of Actinobacillus actinomycetecomitans isolated from juvenile and adult periodontitis patients was compared to that of 15 reference strains of oral and nonoral Actinobacillus species and Haemophilus aphrophilus. Trimethylsilyl derivatives of the fatty acid methyl esters were analyzed by gas-liquid chromatography. The predominant fatty acids of all 40 strains examined were 14:0, 3-OH 14:0, 16 delta, and 16:0. Actinobacillus seminis (ATCC 15768) was unlike the other strains examined because of a greater amount of 14:0 detected. The soluble protein analysis using polyacrylamide gel electrophoresis revealed that A. actinomycetemcomitans, H. aphrophilus, and nonoral Actinobacillus species possessed distinct protein profiles attesting to the validity of separating these organisms into different species. Established biotypes of A. actinomycetemcomitans could not be differentiated on the basis of fatty acid or protein profiles.

Enzymatic characterization of some oral and nonoral gram-negative bacteria with the API ZYM system

The API ZYM system (Analytab Products, Plainview, N.Y.), containing 19 chromogenic substrates, was utilized semiquantitatively to detect extracellular acid and alkaline phosphatases, aminopeptidases, proteases, esterase-lipase, phosphoamidase, and glycosidases in 128 oral and nonoral isolates of black-pigmented Bacteroides, Actinobacillus, Haemophilus aphrophilus, Capnocytophaga, Fusobacterium nucleatum, Wolinella recta, and Veillonella parvula. In the black-pigmented Bacteroides group of organisms, a strong trypsin reaction was present in Bacteroides gingivalis (oral species) but not in Bacteroides asaccharolyticus (nonoral species). Bacteroides melaninogenicus subsp. melaninogenicus, in contrast to Bacteroides melaninogenicus subsp. intermedius, exhibited strong N-acetyl-beta-glucosaminidase activity. H. aphrophilus produced beta-galactosidase and alpha-glucosidase, but the closely related Actinobacillus actinomycetemcomitans did not. Capnocytophaga was distinct with respect to strong aminopeptidase reactions. This study showed that a wide range of enzymes which have the potential of causing tissue injury and inflammation can be elaborated from major oral gram-negative species. Also, the API ZYM system appears to be a valuable adjunct to traditional biochemical testing in identifying oral gram-negative species.

Identification of Bacteroides gingivalis by fluorescent antibody staining

Reactivity with the conjugates to the 4 serogroups A, B, C and C-1 of the former taxon Bacteroides melaninogenicus and with antisera to B. gingivalis and to oral strains of B. melaninogenicus subsp. intermedius, was studied by fluorescent antibody staining (FAS) on strains representative of the black-pigmented Bacteroides: B. asaccharolyticus, B. melaningogenicus subsp. intermedius, B. melaninogenicus subsp. melaninogenicus, B. melaninogenicus subsp. levii, B. melaninogenicus subsp. macacae and B. gingivalis. The strains of B. gingivalis only reacted with the homologous antiserum and failed to react with any of the other immunoreagents tested indicating that the oral strains of asaccharolytic black- pigmented Bacteroides belong to a serogroup distinct from those currently serogrouped. This serological characteristic corroborates the definition of the new species B. gingivalis which has been proposed on the basis of phenotypic and genetic characteristics different from that of B. asaccharolyticus and can be used for their discrimination. FAS appears to be a reliable method for identification of B. gingivalis, a suspected major periodontopathic organism.

Black-pigmented Bacteroides spp. in the human oral cavity

Five healthy children under 6 years of age, five healthy adults, and 10 adult periodontitis patients were examined for the prevalence and distribution of black-pigmented Bacteroides in the oral cavity. A total of 13 samples was obtained from each individual, including four supragingival and four subgingival dental plaques, dental occlusal surface, buccal mucosa, dorsal tongue, tonsil, and whole saliva. Black-pigmented Bacteroides were recovered from nine adult periodontitis patients. Healthy adults harbored the organisms in low incidence and proportions, whereas the children exhibited no cultivable black-pigmented Bacteroides. The organisms were isolated in highest proportions from dental plaque, especially subgingival plaque, and from the tonsil area, indicating that these sites constitute the organisms' primary ecological niche in the oral cavity. The predominant isolate was Bacteroides melaninogenicus subsp. intermedius followed by Bacteroides gingivalis and B. melaninogenicus subsp. melaninogenicus. B. melaninogenicus subsp. levii constituted low proportions of supragingival microflora of one adult periodontitis patient. A positive correlation was demonstrated between the proportion of black-pigmented Bacteroides (mainly B. melaninogenicus subsp. intermedius) and both the severity of gingival inflammation and the periodontal pocket depth, suggesting that these organisms may contribute to the pathogenesis of certain forms of periodontal disease.

Serum antibodies to oral Bacteroides asaccharolyticus (Bacteroides gingivalis): relationship to age and periondontal disease

An enzyme-linked immunosorbent assay microplate method was used for measuring levels of antibody specific for the oral serotype of Bacteroides asaccharolyticus (Bacteroides gingivalis) in serum samples obtained from umbilical cords, infants, children, periodontally normal adults, and edentulous adults. Serum from patients with various periodontal diseases, including adult periodontitis, localized juvenile periodontitis, generalized juvenile periodontitis, post-localized juvenile periodontitis, and acute necrotizing ulcerative gingivitis, were also studied. A positive correlation between increase in age and increase in both prevalence and level of specific antibody in the G, A, and M classes of immunoglobulins was observed. This indicates that antibodies reactive with oral B. asaccharolyticus found in up to 84% of normal adults are natural antibodies, presumably with a protective role. Among the patient groups, those with adult periodontitis were found to have levels of immunoglobulin G antibodies to oral B. asaccharolyticus that were five times higher than the antibody levels found in control subjects. The levels of IgG antibodies to this organism in the other patient groups were comparable to the levels found in the control group. However, 50% of the individuals in the generalized juvenile periodontitis group had high levels of immunoglobulin G antibodies to B. asaccharolyticus, suggesting heterogeneity with respect to immune response in these patients. These results indicate that antibodies to oral B. asaccharolyticus (B. gingivalis) occur at low levels in most normal children and adults and that the rise in titer of the specific antibodies of each major class of immunoglobulins parallels the ontogenic change in serum levels of that isotype. In contrast, there is a marked increase in titer of immunoglobulin G antibodies to oral B. asaccharolyticus in the group of patients with adult periodontitis and in patients with the generalized form of juvenile periodontitis.

Actinobacillus actinomycetemcomitans in human periodontal disease: a cross-sectional microbiological investigation

Actinobacillus actinomycetemcomitans is a facultative gram-negative bacterium which has been associated with severe oral and nonoral infections. This study examined its occurrence in the oral cavities of 10 normal juveniles, 11 normal adults, 10 juvenile periodontitis patients, and 12 adult periodontitis patients. Four deep periodontal pockets and two normal periodontal sites were sampled in the diseased patients, and six normal periodontal sites were sampled in the healthy individuals. In all subjects samples were obtained from the cheek, tongue, and saliva. Samples from a total of 172 normal periodontal sites, 83 deep periodontal pockets, 42 cheek mucosae, 42 tongue dorsa, and 42 salivas were examined. Isolation was performed by using a medium for selective isolation of A. actinomycetemcomitans (Trypticase soy agar [BBL Microbiology Systems] supplemented with 10% serum and 75 mug of bacitracin per ml). The carrier rates were 20% for normal juveniles, 36% for normal adults, 50% for adult periodontitis patients, and 90% for juvenile periodontitis patients. A. actinomycetemcomitans was on average recovered in about fivefold-higher numbers from infected deep periodontal pockets than from infected normal subgingival areas. Samples of periodontal pockets generally contained 100-fold-more cells of A. actinomycetemcomitans than did samples of the cheek, tongue, and saliva. A. actinomycetemcomitans is commonly isolated from patients with juvenile periodontitis, often isolated from patients with adult periodontitis, and occasionally isolated from normal juveniles and adults. Its primary oral ecological niche appears to be dental plaque and periodontal pockets.

Antigenic studies of oral and nonoral black-pigmented Bacteroides strains

Antigens of several oral and nonoral strains of Bacteroides asaccharolyticus (proposed classification of oral B. asaccharolyticus, Bacteroides gingivalis), Bacteroides melaninogenicus subsp. intermedius, B. melaninogenicus subsp. melaninogenicus, and B. melaninogenicus subsp. levii were identified in soluble preparations obtained by sonication, autoclaving, and NaOH treatment of whole bacterial cells. The sonicate preparations contained the most complete representation of soluble antigens using antisera to the whole organism in gel precipitation tests. Among strains of B. melaninogenicus subsp. intermedius many common antigens were detected, and no consistent antigenic differences were seen between strains from oral and nonoral sites. None of the antigens of B. melaninogenicus subsp. intermedius reacted with sera raised to several strains of oral or nonoral B. asaccharolyticus, nor did antigens prepared from the latter strains react with antisera to B. melaninogenicus subsp. intermedius. At least one common antigen was shared by strains of B. melaninogenicus subsp. intermedius and strains of B. melaninogenicus subsp. melaninogenicus; however, subspecies-specific antigens were also found. Antigens from and antisera to oral and nonoral strains of B. asaccharolyticus did not react with sera to and antigens from B. melaninogenicus subsp. melaninogenicus. Strains of B. asaccharolyticus isolated from the oral cavity were antigenically distinct from strains of B. asaccharolyticus obtained from nonoral sites and lesions. This lack of cross-reactivity between the oral and nonoral strains of B. asaccharolyticus together with recent findings of marked genetic differences between oral and nonoral strains of B. asaccharolyticus suggest that these groups of organisms may represent different species.