In vitro evaluation of contemporary beta-lactam drugs tested against viridans group and beta-haemolytic streptococci.
Streptococci continue to be prevalent causes of mild as well as of serious, life-threatening infections. Furthermore, some species harbor antimicrobial resistances (pneumococcus, viridans gr. streptococci) that compromise effective chemotherapy with beta-lactam drugs or other antimicrobial classes. In this study, the potency and spectrum of 12 beta-lactams was assessed versus 274 contemporary isolates of viridans group and beta-haemolytic streptococci using reference methods. Cefotaxime and ceftriaxone (MIC90s, 0.015 to 2 micrograms/ml, 84 to 100% susceptible) were consistently most potent among the agents tested. Ceftazidime (MIC90s, 0.25 to 8 micrograms/ml) and ticarcillin (MIC90s, 0.5 to > 32 micrograms/ml) were least active among the cephalosporins and penicillins, respectively. When 25% pooled serum was added to the reference test medium, ceftriaxone activity decreased fourfold, and cefotaxime remained highly active. As penicillin/beta-lactam-resistant streptococci with altered penicillin-binding protein target sites become more prevalent, only a few "third-generation" cephems seem to have sustained activity when used alone or possibly with a carefully selected co-drug. Routine testing of these species against beta-lactams and alternative drugs should be encouraged to detect emerging resistance patterns.
Pfaller
M A
MA
Department of Pathology, University of Iowa College of Medicine, Iowa City 52242, USA.
Jones
R N
RN
D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002439:Cefotaxime / Q000494:pharmacology; D002442:Ceftazidime / Q000494:pharmacology; D002443:Ceftriaxone / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D008826:Microbial Sensitivity Tests; D010406:Penicillins / Q000494:pharmacology; D013290:Streptococcal Infections / Q000188:drug therapy; D013291:Streptococcus / Q000187:drug effects* / Q000302:isolation & purification; D013982:Ticarcillin / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D010406:Penicillins; D002443:Ceftriaxone; D000667:Ampicillin; D002442:Ceftazidime; D013982:Ticarcillin; D002439:Cefotaxime