In vitro susceptibility of Staphylococcus aureus towards amoxycillin-clavulanic acid, penicillin-clavulanic acid, dicloxacillin and cefuroxime.
Sixty-three Staphylococcus aureus isolates with a wide distribution in quantitative beta-lactamase production were tested in vitro against amoxycillin and penicillin in combination with clavulanic acid to establish the influence of total amount of beta-lactamase present on the ability of clavulanic acid to protect against beta-lactamase degradation. The beta-lactamase stability of cefuroxime and dicloxacillin was also evaluated. MIC was determined by agar dilution using Mueller-Hinton agar with both a conventional as well as a 100 times higher inoculum. The strains were tested both with and without induction of the beta-lactamase production. Clavulanic acid was highly effective in protecting against beta-lactamase degradation of both penicillin and amoxycillin. Even when using a high inoculum of strains with induced beta-lactamase production, all strains had MICs below the NCCLS breakpoint of 4/2 mg/l for amoxycillin-clavulanic acid. Both cefuroxime and dicloxacillin were highly stable against staphylococcal beta-lactamase degradation. This study encourages further in vivo evaluation of amoxycillin-clavulanic acid for severe staphylococcal infections.
Skov
Robert
R
Department of Research and Development, Statens Serum Institut, Copenhagen, Denmark. rsk@ssi.dk
Frimodt-Møller
Niels
N
Espersen
Frank
F
D019980:Amoxicillin-Potassium Clavulanate Combination / Q000494:pharmacology*; D002444:Cefuroxime / Q000494:pharmacology; D004009:Dicloxacillin / Q000494:pharmacology; D004359:Drug Therapy, Combination / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D010406:Penicillins / Q000494:pharmacology*; D013203:Staphylococcal Infections / Q000188:drug therapy; D013211:Staphylococcus aureus / Q000187:drug effects*; D018709:Statistics, Nonparametric; D001618:beta-Lactamases / Q000378:metabolism
D010406:Penicillins; D019980:Amoxicillin-Potassium Clavulanate Combination; D004009:Dicloxacillin; D001618:beta-Lactamases; D002444:Cefuroxime