In vitro activity of antimicrobial agents against Acinetobacter calcoaceticus

The aim of this study was to evaluate the in vitro activity of several new microbial agents against 96 Acinetobacter calcoaceticus isolates. Among several new beta-lactams, imipenem, a new, broad-spectrum, highly potent penem, was the most active drug in vitro against these strains, with a geometric mean MIC of about 0.3 mg/l. Ceftazidime and ceftizoxime also demonstrated good in vitro activity with geometric mean MICs of 6 mg/l and 7 mg/l respectively. Among new quinolones, ciprofloxacin, ofloxacin and pefloxacin were substantially active in vitro: geometric means were 0.8, 0.9 and 1.5 mg/l respectively. A progressive increase in resistance to aminoglycosides has been observed and 80 to 90% of isolates were resistant to all but amikacin, tobramycin and habekacin, which showed geometric mean MICs of 7.0, 6.0 and 1.2 mg/l.