Grouping of some clinically relevant gram-positive rods by automated fatty acid analysis. Diagnostic implications

One hundred and ninety-four strains of aerobically growing Gram-positive rods of the genera Corynebacterium, Actinomyces, Arcanobacterium, Erysipelothrix, Listeria, Oerskovia, Nocardia, Rhodococcus, and of unnamed Center for Disease Control (CDC) groups were checked for cellular fatty acid profiles with the microbial Identification System (Microbial ID, Newark, Del., USA). In order to obtain unified data usable for the clinical laboratory, 24 or 48 h sheep blood agar cultures were used. It was thought that grouping and perhaps identification could be aided by this approach. With the aid of numerical analysis, four groups (two consisting of two subgroups each) were established. The discriminatory ability of the scheme, however, was only 77.2%, indicating that grouping of an unknown isolate could be done with some accuracy, but that speciation would still require biochemical testing.