CORRELATION OF IN-VITRO SUSCEPTIBILITY TESTING RESULTS FOR AMOXICILLIN-CLAVULANATE AND AMPICILLIN-SULBACTAM USING A PANEL OF BETA-LACTAMASE-PRODUCING ENTEROBACTERIACEAE - BRIEF REPORT

Correlation between in vitro susceptibility results for amoxicillin-cl avulanate (AMC) and ampicillin-sulbactam (SAM) was studied using 136 c linical and control strains of Enterobacteriaceae harboring TEM-1, SHV -1 or OXA-1-like beta-lactamases. Determination of minimal inhibitory concentration of antibiotics was performed by agar dilution. The beta- lactamases were initially characterized using isoelectric focusing. Fu rther identification was done by DNA hybridization with or without pri or PCR amplification. All strains sensitive to SAM were found to be se nsitive also to AMC. In contrast, among those susceptible to AMC, only 50% were sensitive to SAM while 36% gave intermediate results and 14% were resistant. Major differences were found solely among SHV-produce rs while minor differences occurred mostly among TEM-producers. This p henomenon is probably related to the differential activities of clavul anate and sulbactam against various beta-lactamases. In conclusion, te sting of Enterobacteriaceae isolates for susceptibility to AMC and SAM should be performed and reported individually to avoid erroneous desi gnation of susceptibility.