Predominant obligate anaerobes in human carious dentin.

With the adoption of an anaerobic glove box system, we isolated and identified the predominant micro-organisms in lesions of carious dentin from four permanent third molars. The overwhelming majority of the micro-organisms isolated from both shallow and deep layers of carious dentin were obligate anaerobes, suggesting that conditions in the dentin were strictly anaerobic. The predominant obligate anaerobes were Gram-positive rods which were identified as members of the following genera: Propionibacterium, Eubacterium, Arachnia, Lactobacillus, Bifidobacterium, and Actinomyces. Clostridia, Gram-negative rods (Bacteroides and Fusobacterium) and Gram-positive cocci (Peptococcus, Peptostreptococcus, and Streptococcus) were also isolated, although they constituted a minor part of the flora.