Journal of Antimicrobial Chemotherapy, Vol 39, 89-93, Copyright © 1997 by The British Society for Antimicrobial Chemotherapy
AM Fornara, F Danel and DM Livermore
MICs of piperacillin with tazobactam or sulbactam (4 mg/L) were higher at
pH 6.5 than at pH 8.0 for Escherichia coli transconjugants with TEM- 1 or
TEM-2 enzymes, but not for those with TEM-3 or TEM-10 enzymes.
Investigation showed: (i) all four enzymes were less sensitive to sulphones
at pH 6.5 than at pH 8.0; (ii) pH effects on MICs arose also for the TEM-3
and TEM-10 producers at lower sulphone concentrations; (iii) the TEM-3 and
TEM-10 producers formed less enzyme than those with TEM-1 and TEM-2 and
(iv) pH effects on the MICs for TEM-1 producers depended on enzyme
quantity. We conclude that all four TEM enzymes have pH-dependent
susceptibility to sulphones, but whether this affects MICs depends on the
inhibitor:enzyme ratio achieved in the bacteria.
JOURNAL ARTICLE
pH effects on the inhibition of extended-spectrum and classical TEM beta-lactamases by penicillanic acid sulphones
Royal London School of Medicine and Dentistry, UK.
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