Risk factors for acquisition of gentamicin-resistant enterococci. A multivariate analysis.

High-level gentamicin resistance in enterococci is an increasing problem in hospitalized patients. Multiple risk factors for the acquisition of these organisms have been identified, but these risk factors are highly interrelated, and it has been unclear which of them are truly important. We performed a case-control study comparing 37 patients colonized or infected with resistant enterococci with 84 patients with susceptible strains. Crude odds ratios were significant for nosocomial acquisition, duration of hospitalization, hospitalization on the medical service or in an intensive care unit, number and duration of antibiotics received, and receipt of several individual antibiotics. By logistic regression, hospitalization longer than 2 weeks (odds ratio, 5.4; 95% confidence interval, 1.7 to 17) and receipt of five or more antibiotics (odds ratio, 26; 95% confidence interval, 2.8 to 250) were significantly associated with colonization or infection with resistant enterococci. Patients with these latter two risk factors may be targeted in infection control efforts.