Simple identification of anaerobic bacteria to genus level using typical antibiotic susceptibility patterns

Simple yet comprehensive identification of anaerobic bacilli is possible to genus level when typical susceptibility patterns of antimicrobial substances are used in combination with the morphological characteristics of the bacteria. Paper discs were soaked with fosfomycin (100 μg), colistin (10 μg), everninomicin B (10 μg) and metronidazole (2 μg) and tested on sheep blood agar in a jar under anaerobic conditions. A dichotomous scheme has been suggested for the differentiation of the following genera: Actinomyces, Bacteroides, Bifidobacterium, Clostridium, Eubacterium, Fusobacterium, Lactobacillus, Leptotrichia, Propionibacterium and Selenomonas. The method gave preliminary results which can be used as guidance for subsequent species identification and for therapeutic advice, as antibiotic susceptibility depends very much on the genus of anaerobic bacilli.