IN-VITRO ACTIVITIES OF QUINOLONES, BETA-LACTAMS, TOBRAMYCIN, AND TRIMETHOPRIM-SULFAMETHOXAZOLE AGAINST NONFERMENTATIVE GRAM-NEGATIVE BACILLI

From 1991 to 1995, 8,975 nonfermentative gram-negative bacilli were is olated from patients at The Ohio State University Medical Center: 71% Pseudomonas aeruginosa, 14% Stenotrophomonas maltophilia, 7.6% Acineto bacter baumannii, and < 2% each of 25 other species. The MICs of trova floxacin (CP-99,219), ciprofloxacin, ofloxacin, ampicillin-sulbactam, piperacillin, piperacillin-tazobactam, ceftazidime, cefoperazone, ceft riaxone, imipenem, tobramycin, and trimethoprim-sulfamethoxazole (TMP- SMZ), were determined for 308 isolates, representing 13 species, by a standardized broth microdilution method, The activities of all drugs w ere species dependent, The fluoroquinolones had inconsistent activity against most species, although several relatively uncommon nonfermente rs were consistently susceptible or resistant, Trovafloxacin was consi derably more active than ciprofloxacin and ofloxacin against S. maltop hilia, A, baumannii, and several less common species, Among the beta-l actams, relative activities varied considerably; overall, imipenem had the broadest spectrum of activity but was inactive against S. maltoph ilia and Burkholderia cepacia isolates, Tobramycin and TMP-SMZ had ste reotypic spectra of activity. Tobramycin was active against most speci es except S, maltophilia, Alcaligenes xylosoxidans subsp, xylosoxidans , Burkholderia spp,, and Weeksella virosa, TMP-SMZ, was active against most species except P. aeruginosa and Pseudomonas fluorescens-putida. A review of laboratory records indicated few changes in susceptibilit y patterns from 1991 to 1995; the only clear trend was toward increasi ng P. aeruginosa resistance to all classes of drugs.