Retrospective Resistance Pattern of Clinical Isolates In Vitro Against Imipenem and Other Antimicrobial Agents Between 1986 and 1989

Summary

The in vitro activity of imipenem and several other antibacterial agents (including broad spectrum penicillins, expanded spectrum cephalosporins, and fluoroquinolones) was assessed against 130 033 clinical isolates of Gram-negative aerobic bacteria, Gram-positive aerobic bacteria, and anaerobic bacteria, collected in Germany between 1986 and 1989. Overall, 97.4% of the isolates were inhibited by an imipenem concentration of 4 mg/L. Most isolates of Xanthomonas maltophilia and Pseudomonas cepacia were resistant to imipenem between 1986 and 1989. However, when these 2 species are excluded, the frequency of resistance of the remaining isolates is < 1% each for Gram-negative, Gram-positive, and anaerobic species, indicating a level of activity of imipenem greater than that of any of the 18 comparative antibacterial agents.

Despite extensive clinical use in Germany between 1986 and 1989, the activity of imipenem against all bacterial species remained virtually unchanged. Of particular note is the maintenance of activity against P. aeruginosa, with only 1% of 1197 isolates being resistant in 1989. In contrast, a trend to an increasing incidence of resistance of some species was seen with a few of the other antimicrobials: the aminoglycosides and mezlocillin (X. maltophilia and P. cepacia); mezlocillin, piperacillin, and cefoperazone (Serratia spp.); cefuroxime (Serratia spp, Morganella morganii, and Proteus vulgaris); flucloxacillin and ofloxacin (coagulase-negative staphylococci); and the fluoroquinolones (Bacteroides fragilis). However, the clinical significance of some of these trends is negligible.