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We report a case of non-clostridial gas gagrene caused by odontogenic infection.A 35-year-old man was referred to our hospital because of swelling in the neck and the anterior chest. Crepitation was evident beneath the skin and computed tomography (CT) showed abundant gas extending from the left parapharyngeal space and the bilateral submandibular space to the anterior chest through the neck. He was admitted immediately and underwent drainage from the cervical incision and surgical debridement with the administration of antibiotics. Hyperbaric oxygen treatment was performed from the day after the operation because clostridial gas gangrene could not be ruled out by microscopic examination. After treatment, the patient recovered and was discharged on the 44th postoperative day. Bacteriologic examination revealed Bacteroides buccae and anaerobic gram positive cocci.

– The hydrophobicities of human polymorphonuclear leukocytes (PMNLs) and Bacteroides buccae, B. oris, B. oralis, B.veroralis, B. buccalis, B. heparinolyticus, B. intermedius, B. denticola, B. loescheii, B. melaninogenicus, Porphyromonas gingivalis, P. endodontalis, Wolinella recta, and Eubacterium yurii were studied by the hexadecane method. The majority of the strains were equally or less hydrophobic than the PMNLs. Only in the case of E. yurii and the only strain of B. buccalis were all strains more hydrophobic than the PMNLs. However, some strains of B. intermedius, B. oris, B. denticola, and P. gingivalis were also more hydrophobic than the PMNLs. With the exception of B. intermedius and species with a crystalline surface protein layer (S-layer), the strains of all other species with a thick capsule were more hydrophilic than the strains with little or no extracellular polymeric material. All strains of the S-layer species were either quite hydrophilic or hydrophobic depending on the species, totally irrespective of the presence of the capsule. The results suggest that the S-layers of oral anaerobic bacteria may be important determinants of cell surface hydrophobicity.

We characterized clinical isolates previously identified in our laboratory as Bacteroides ruminicola, the human strains of which are now classified as Bacteroides oris and Bacteroides buccae. A total of 72 isolates (55 B. buccae isolates and 17 B. oris isolates) recovered over a 10-year period were studied. They were differentiated from each other by special-potency antibiotic disks and the RapID-ANA system. The two organisms were associated with a variety of infections, the majority being pleuropulmonary (29.2%) and infections of the head and neck region (27.8%). The infections were always polymicrobial, usually with more than five organisms per specimen. A total of 44% of the B. oris strains and 27% of the B. buccae strains were resistant to penicillin G (breakpoint, 2 U/ml), and this correlated with the presence of beta-lactamase. Although B. oris and B. buccae are found with some frequency in human infections, they are present primarily as components of a mixed flora.

SUMMARY: In Bacteroides buccae, a hexagonally arranged periodic structure was found in the outer membrane (OM), in addition to hexagonal lattices present in its external surface layer (S-layer). This crystalline OM protein (COMP) was present as patches on the concave fracture face (the outer leaflet) of the OM in freeze-fractured cells. Occasionally, hexagonally arranged structures could also be seen on the convex fracture face of the OM as ‘fingerprints’ of the COMP. The OM proteins were isolated and analysed by gel electrophoresis. The major band protein had an apparent molecular mass of 17 kDa. Whether the minor band proteins are also components in the structure of the COMP remains to be elucidated. Other oral Gram-negative anaerobic rods studied did not show any periodicity in their OM.

Bacteroides buccae is among the few human oral species reported with an S-layer (Kornman and Holt 1981). The periodic arrangement of the lattice has been reported to be hexagonal (Ranta et al. 1983, Haapasalo et al. 1985, Sjogren et al. 1985).

The type strain of Bacteroides pentosaceus Shah and Collins and the type strain of Bacteroides buccae Holdeman et al. have more than 80% deoxyribonucleic acid homology with the type strain of Bacteroides capillus Kornman and Holt, and therefore the three names are subjective synonyms. Since B. buccae Holdeman et al. was the first validly published name applied to this taxon, B. capillus and B. pentosaceus are later synonyms of B. buccae.