The differentiation of asaccharolytic anaerobic gram-positive cocci by protein electrophoresis

Conventional biochemical and antibiotic sensitivity tests were used to allocate 87 clinical isolates of anaerobic gram-positive cocci to currently recognised species, in comparison with type and other authentic reference strains. Whole-cell protein electrophoresis was then performed with extracts of each strain. Allowing for difficulties of standardisation, it was possible to allocate most of the organisms to species-related groups on the basis of protein patterns. Organisms identified conventionally as Peptostreptococcus anaerobius and P. micros formed homogeneous groups by protein electrophoresis. There was evidence for heterogeneity amongst strains identified as P. asaccharolyticus (two groups, including P. indolicus), P. prevotii and P. magnus. However, aberrant P. prevotii strains were allocated to the P. asaccharolyticus groups, leaving a homogeneous P. prevotii group, and if P. variabilis were re-instated as a species, the remaining P. magnus strains could be divided into two groups. Of the anaerobic gram-positive cocci in the National Collection of Type Cultures deposited by Hare, Group IV is P. magnus, Group IX is P. micros and Groups I, III and VIII appear to be related to the butyrate-producing species P. asaccharolyticus and P. prevotii, but are strongly saccharolytic.