MULTICENTER EVALUATION OF ANTIMICROBIAL RESISTANCE TO 6 BROAD-SPECTRUM BETA-LACTAMS IN COLOMBIA USING THE ETEST METHOD

The need for comprehensive and quantitative accurate antimicrobial res istance surveillance systems has become acute as a guide to problem re cognition and to focus local interventions. A multilaboratory (10 medi cal centers) Colombia surveillance project was initiated in early 1997 to monitor the potency and spectrum of six (cefepime, cefotaxime, cef tazidime, cefoperazone/sulbactam, aztreonam, and imipenem) broad-spect rum antimicrobial agents tested against 100 organisms per participant center (802 strains). Ten groups of organisms were tested by a referen ce-quality method (Etest; AB BIODISK, Solna, Sweden) with results vali dated by concurrent quality control and additional challenge strain an alysis. Results from nine qualifying medical centers were tabulated, a nd 95.7 to 96.8% of quality assurance tests were within expected range s. Only cefepime (90.1-100.0% susceptible) and imipenem (96.3-100.0%) were active against all Enterobacteriaceae at >90% of susceptible isol ates using the breakpoint concentrations recommended by the National C ommittee for Clinical Laboratory Standards. Among ceftazidime- (or cef otaxime- or aztreonam-) resistant Enterobacter spp. and Citrobacter fr eundii, cefepime remained active, but not cefoperazone with sulbactam. Escherichia coli and Klebsiella spp. strains having resistance phenot ypes consistent with extended spectrum beta-lactamase production were discovered in approximately 5 to 10% of isolates. All tested drugs exc ept ceftazidime (31.8-57.7% susceptible) were active against >94% of o xacillin-susceptible staphylococci. Similar rates of resistance (9.1-1 4.8%) were observed in Pseudomonas aeruginosa for five of six drugs (n ot cefotaxime; 15.9% of strains were susceptible). Acinetobacter spp. isolates were most susceptible to imipenem (95.8%), cefepime (86.1%), and cefoperazone/sulbactam (83.3%). Overall for the 1997 order of anti microbial spectrums for these tested compounds was: imipenem (96.6%) > cefepime (93.6%) > cefoperazone/sulbactam (90.5%) > cefotaxime (74.9% ) > aztreonam (74.3% for Gram-negative bacilli only) > ceftazidime (73 .2%). These data should be used to guide empiric regimens in Colombia, and additionally will provide a resistance statistical baseline to wh ich future studies in this nation can be compared. (C) 1997 Elsevier S cience Inc.