In vitro effect on group A streptococci of loracarbef versus cefadroxil, cefaclor and penicillin V.
The in vitro activity of loracarbef, penicillin V, cefaclor and cefadroxil against log and stationary phase cultures of group A streptococci was compared. MICs and MBCs were determined with the broth dilution method and by a modified agar plate dilution technique where the beta-lactams were inactivated after the MICs were determined allowing inhibited but not killed organisms to grow on further incubation. The MICs of loracarbef and the two cephalosporins were 16-32 times higher than those of penicillin V. In plate dilution the MBC/MIC ratios of all agents were < or = 2 for log phase cultures. With stationary phase cultures, especially in the broth dilution test, the MBC/MIC ratios of loracarbef and the two cephalosporins were > or = 32 for a large number of strains. The phenotype response of stationary phase cultures to beta-lactam antibiotics may not only be related to the physiological status of the streptococci, to the culture conditions and to the beta-lactam under test. The present investigation indicated that the phenotypic response was also an intrinsic property of certain strains.
Kamme
C
C
Department of Medical Microbiology, University Hospital of Lund, Sweden.
Petersson
A C
AC
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002433:Cefaclor / Q000494:pharmacology; D002434:Cefadroxil / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D008826:Microbial Sensitivity Tests / Q000379:methods*; D010404:Penicillin V / Q000494:pharmacology; D010612:Pharyngitis / Q000188:drug therapy / Q000382:microbiology; D013290:Streptococcal Infections / Q000188:drug therapy / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D002434:Cefadroxil; C054920:loracarbef; D002433:Cefaclor; D010404:Penicillin V