Risk factors for fluoroquinolone resistance in nosocomial Escherichia coli and Klebsiella pneumoniae infections.

BACKGROUND The incidence of fluoroquinolone (FQ) resistance has increased markedly in recent years. Even in the common nosocomial pathogens Escherichia coli and Klebsiella pneumoniae, in which the emergence of FQ resistance was believed to be unlikely, increasing resistance to these agents has been noted. Risk factors for FQ resistance in these pathogens remain unknown. Although FQs are important components of the present antimicrobial arsenal, their continued usefulness is threatened by rising FQ resistance. OBJECTIVE To identify risk factors for nosocomial FQ resistance. METHODS A case-control study of hospitalized patients with infections due to FQ-resistant and FQ-susceptible E coli and K pneumoniae occurring between January 1, 1998, and June 30, 1999. RESULTS We included 123 patients with nosocomial FQ-resistant infections and 70 randomly selected patients with nosocomial FQ-susceptible infections. Independent risk factors (adjusted odds ratio [95% confidence interval]) for FQ resistance were (1) recent FQ use (5.25 [1.81-15.26]); (2) residence in a long-term care facility (3.65 [1.64-8.15]); (3) recent aminoglycoside use (8.86 [1.71-45.99]); and (4) older age (1.03 [1.01-1.06]). CONCLUSIONS Recent FQ use, residence in a long-term care facility, recent aminoglycoside use, and older age were all noted to be independent risk factors for FQ resistance among patients with nosocomial E coli and K pneumoniae infections. Efforts should be directed at recognition and modification of these risk factors to curb the rise in FQ resistance and preserve the utility of these agents in the treatment of common nosocomial gram-negative infections.