The Journal of Medical Microbiology, Vol 38, Issue 2 114-117, Copyright © 1993 by Society for General Microbiology
Stability of cefdinir (C1-983, FK482) to extended-spectrum plasmid-mediated beta-lactamases
D. J. Payne and S. G. Amyes
Department of Medical Microbiology, Medical School, University of Edinburgh.
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.
