Streptococcus milleri causing infection in man.

We describe the microbiological and morphological characteristics of 151 strains of Streptococcus milleri isolated during the course of routine bacteriological investigations. Although these strains formed a fairly heterogeneous group, several constant features were identified which typify the species. Strept. milleri emerged as a major cause of pyogenic infection, clinical disease being characterized by localized collections of pus in almost every organ system. Bacteraemia due to Strept. milleri was a significant indicator of the presence of an occult abscess. Endocarditis was rare. The penicillins or erythromycin remain the drugs of choice for treating infections caused by this organism.