Antimicrobial resistance of Pseudomonas aeruginosa strains isolated from surgical infections in a 7-year period at a general hospital in Venezuela

Background: By definition, the term "surgical infection" implies that surgery plays the major role in therapy, whereas antimicrobial chemotherapy is only supplementary. Despite this view, the efficacy of such drugs is relevant, and for this reason, drug activity surveillance is necessary, especially for opportunistic and nosocomial pathogens such as Pseudomonas aeruginosa. We evaluated bacterial isolates from patients with suspected surgical infections in a hospital of Caracas, Venezuela (West General Hospital) between 1997 and 2003. Methods: Clinical samples were processed and identified with standard cultures and biochemical tests. The antimicrobial susceptibility of the isolates in vitro was assessed by an agar disk diffusion method using Mueller-Hinton agar, as recommended by the National Committee for Clinical Laboratory Standards (now the Clinical and Laboratory Standards Institute). Isolates were tested against 22 drugs, including piperacillin, ceftazidime, cefoperazone, amikacin, gentamicin, ciprofloxacin, meropenem, and imipenem. Results: From a total of 16,287 bacterial strains isolated from surgical infections during the study period, 243 (1.5%) were P. aeruginosa. Of this total, 30.9% were resistant to gentamicin, 26.3% to tobramicin, 23.0% to cefoperazone, 22.8% to piperacillin, 22.5% to ciprofloxacin, 17.6% to amikacin, 13.6% to imipenem, and 12.9% to meropenem. The best antimicrobial activity was observed with cefepime (90.1% susceptible strains, 1.9% intermediate resistance, and 8.0% resistant strains) and aztreonam (77.7% susceptible strains, 15.2% intermediate resistance, and 7.1% resistant strains). Conclusions: In our setting, cefepime is most active against strains of P. aeruginosa. In comparison with third-generation cephalosporins, cefepime may be less likely to induce resistance. Surveillance of antimicrobial activity should be done periodically to guide therapy of surgical infections.