Stability of cefdinir (C1-983, FK482) to extended-spectrum plasmid-mediated beta-lactamases.
Fourteen plasmid-encoded extended-spectrum beta-lactamases were purified from Escherichia coli transconjugants of original clinical isolates. The Vmax, Km and Vmax/Km were each determined for ampicillin, carbenicillin, cephaloridine, cephalexin, cefuroxime, cefixime, cefdinir, ceftazidime and cefotaxime as substrates with eight of these enzymes and with the narrow-spectrum beta-lactamase, TEM-1. The relative rates of hydrolysis of ampicillin, cephaloridine, cephalexin, cefuroxime, cefixime, cefdinir, ceftazidime and cefotaxime were also determined for the remaining six enzymes. Cefdinir had Vmax/Km or relative rates of hydrolysis values either equal to or lower than ampicillin, cephaloridine, cephalexin and cefotaxime for all the enzymes tested. Overall, cefdinir was more stable to the 15 beta-lactamases tested than either cefuroxime or cefixime; however, ceftazidime was more stable than cefdinir to hydrolysis by eight of the enzymes tested.
Payne
D J
DJ
Department of Medical Microbiology, Medical School, University of Edinburgh.
Amyes
S G
SG
D000077525:Cefdinir; D002511:Cephalosporins / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology; D010957:Plasmids; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
D002511:Cephalosporins; D000077525:Cefdinir; D001618:beta-Lactamases