Antimicrobial activity of sultamicillin against clinical isolates from upper respiratory tract infections II

Abstract

In an attempt to examine the effect of sulbactam (SBT) on beta-lactamase activity, three hundred clinical isolates from the infected upper respiratory tract were tested for MICs and disk sensitivities of ampicillin (ABPC) and sultamicillin (SBTPC). beta-lactamase production was tested using the acidometry disk method (beta-Check, Taito Pfizer Co.). For strains such as Klebsiella spp. which form mucoid type colonies, we used the SS culture medium which, by reducing the influence of huge amounts of capsular material, allows a better reaction to the acidometry disk. Penicillinase, produced by Branhamella catarrhalis, Haemophilus influenzae, Neisseria spp., etc. was detected clearly by direct application of portions of colonies onto acidometry disks. For cephalosporinase, however, a direct application of such fractions resulted in weak reactions. We, therefore, used fractions which had undergone the enzyme induction, and obtained better reactions. Sensitivities of tested bacteria to ABPC and SBTPC were inversely related to MIC values. beta-Lactamase-producing strains showed weaker sensitivity to ABPC than non-producing strains. To SBTPC, however, beta-lactamase-producing strains and non-producing strains showed very similar sensitivity. We thus confirmed that the inhibitory action of SBT to beta-lactamase can well be demonstrated using the disk sensitivity method.