Determination of an inoculum effect with various cephalosporins among clinical isolates of methicillin-susceptible Staphylococcus aureus.
Using 98 clinical methicillin-susceptible Staphylococcus aureus isolates of known beta-lactamase (Bla) type, we found a pronounced inoculum effect for cephalexin (mostly Bla type A and C strains), a mild inoculum effect for cephalothin (especially types B and C), and no inoculum effects for ceftriaxone and cefuroxime. Ceftobiprole showed the lowest MICs at a high inoculum but with a slight increase for Bla-positive versus Bla-negative strains. Since a potential therapeutic effect associated with a cephalosporin inoculum effect has been described, further studies are warranted.
Nannini
Esteban C
EC
Division of Infectious Diseases, Facultad de Ciencias Médicas, Universidad Nacional de Rosario, Rosario, Provincia de Santa Fe, Argentina. enannini@cimero.org.ar
Stryjewski
Martin E
ME
Singh
Kavindra V
KV
Rude
Tom H
TH
Corey
G Ralph
GR
Fowler
Vance G
VG
Murray
Barbara E
BE
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002443:Ceftriaxone / Q000494:pharmacology; D002444:Cefuroxime / Q000494:pharmacology; D002506:Cephalexin / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology*; D002512:Cephalothin / Q000494:pharmacology; D006801:Humans; D008712:Methicillin; D008826:Microbial Sensitivity Tests; D013203:Staphylococcal Infections / Q000188:drug therapy*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000254:growth & development*
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D002443:Ceftriaxone; D002444:Cefuroxime; D002506:Cephalexin; D008712:Methicillin; D002512:Cephalothin