Bacteriologic characteristics and antimicrobial susceptibility of 70 clinically significant isolates of Streptococcus milleri group.

The phenotypical characteristics of 70 clinical isolates of Streptococcus milleri group were analyzed. Association of the three species with particular sites of isolation could not be demonstrated in all cases, but S. anginosus strains predominated in abdominal area, while S. intermedius was isolated mainly in hepatic abscesses. Penicillin G and other beta-lactams showed good in vitro activity against these streptococci, whereas > 10% exhibited resistance to erythromycin and clindamycin. Resistance to tetracycline reached almost 40%. All of the isolates were uniformly susceptible to vancomycin, chloramphenicol, and trimethoprim.