Multidrug-Resistant Gram-Negative Pathogens Multiple Approaches and Measures for Prevention

Abstract

Antimicrobial resistance continues to emerge in our hospitals. Despite the predominance of gram-positive healthcare-associated infections in the past 2 decades, gram-negative pathogens continue to be a concern because of the high mortality from these infections among seriously ill patients. 1,2 Although several alternative antimicrobials active against multidrug-resistant gram-positive pathogens are now available, multi-drug resistant gram-negative pathogens continue to emerge and new alternative therapies are not available. Preventive measures, then, become all the more important. Pseudomonas aeruginosa, Klebsiella pneumoniae, and Enterobacter species are among the most problematic gram-negative pathogens with emerging resistance. Four articles in this month's journal address important issues in the prevention of the emergence of resistance in these pathogens. Lautenbach et al. 3 and Fortaleza et al. 4 study risk factors associated with imipenem resistance 3 ' 4 and ceftazidime resistance 3 in P. aeruginosa. The setting of the study by Fortaleza et al. 4 was a 400-bed general teaching hospital in Campinas, Brazil. Cases in which imipenem-resistant P. aeruginosa strains were recovered (108 patients) and in which ceftazi-dime-resistant strains were recovered (56 patients) were selected during the years 1999-2002. Case-control studies showed that independent risk factors associated with imi-penem resistance in their hospital were transfer from another hospital (perhaps a marker for longer time at risk), receipt of hemodialysis, and use of imipenem, amikacin, or vanco-mycin. Only transfer from another hospital and amikacin use were independent risk factors for recovery of ceftazidime-resistant P. aeruginosa; ceftazidime use was not. The setting of the study by Lautenbach et al. 3 was a 625-bed tertiary care hospital in Philadelphia, Pennsylvania. Cases in which imipenem-resistant P. aeruginosa strains were recovered (142 patients) were identified during the years 1999-2000. Results of a case-control study showed that fluoro-quinolone use, and not imipenem use, was an independent risk factor for recovery of an imipenem-resistant strain. Why was imipenem use a risk factor in one study and not in the other? Both were case-control studies that evaluated imipenem resistance in P. aeruginosa at large teaching hospitals. There was a similar distribution of anatomical sites from which the clinical specimens were isolated and a similar amount of intensive care unit…