THE INFLUENCE OF SULBACTAM ON THE IN-VITRO ACTIVITY OF MEZLOCILLIN, PIPERACILLIN AND CEFOTAXIME (REPRINTED FROM ARZNEIM FORSCH, VOL 41, PG 831, 1991)

In a multicentre study, the in-vitro activity of mezlocillin (MEZ, Che mical Abstract Service (CAS) 51481-65-3), piperacillin (PIP, CAS 61477 -96-1) and cefotaxime (CTX, CAS 63527-52-6) against mexlocillin-resist ant organisms was determined alone and in combination with the beta-la ctamase inhibitor sulbactam (SBT, CAS 68373-14-8). A total of 870 stra ins were investigated (481 Enterobacteriaceae, 57 Pseudomonas aerugino sa, 41 Acinetobacter spp., 194 Bacteroides fragilis and 97 Staphylococ cus spp.). MIC values were determined using the agar dilution test (ae robic organisms) or the microbroth dilution test (Bacteroides spp.) in accordance with Deutsche Industrie fur Normung 58 940. SBT was added in fixed concentrations of 5 mg/l and 10 mg/l. For all combination wit h SBT investigated, the geometric mean of the MIC and the MIC(50) and MIC(90) values were reduced as compared with the antibiotic alone (wit hout SBT). Consequently, the proportion of sensitive strains was appre ciably increased, for example in the Enterobacteriaceas:MEZ 1%, MEZ 10 mg/l SBT 53%: PIP 4%, PIP + 10 mg/l SBT 54%; CTX 52%, CTX + 10 mg/l SBT 68%. The effect of SBT was expecially pronounced on Bacteroides s pp. For this organism, the proportion of sensitive strains rose from 2 % to 97% (MEZ), 6% to 95% (PIP) and from 7% to 98% (CTX). The results show that adding SBT appreciably enhances the activity of MEZ, PIP and CTX against resistant strains of microorganisms, and extends the acti vity spectrum to include anaerobic organisms. Thus the availability of SBT as a single-agent preparation for use in combination with various beta-lactam antibiotics represents a worthwhile enlargement of the th erapeutic armamentarius for treating bacterial infections.