Low-level colonization and infection with ciprofloxacin-resistant gram-negative bacilli in a skilled nursing facility

Background: We report a 1-year surveillance study that evaluates colonizati on and infection with ciprofloxacin-resistant gram-negative bacilli (CR GNB ) and the relation to quinolone use and other possible risk factors in a pr oprietary skilled nursing facility (SNF) with no history of outbreaks. Methods: Rectal swabs obtained quarterly were streaked on MacConkey agar wi th ciprofloxacin discs (5 mu g) to screen fur CR GNB and later were speciat ed and the antimicrobial susceptibilities were confirmed by standardized di sc-diffusion tests. Results: The mean prevalence of CR GNB colonization was 2.6% (range 0.9% to 5.3%). The colonization frequency was higher in the last survey than it wa s in the first survey. CR GNB-colonized strains included Pseudomonas specie s (21%), but more than hall were non-Pseudomonas enteries such as Acinetoba cter baumannii (25%), Proteus mirabilis (17%), and Plovidencia stuartii (13 %). None of the patients who had colonization with CR GNB had subsequent in fections with the same species. Patients with colonization had more exposur e to ciprofloxacin and they were more likely to have been recently admitted from an acute-care hospital and have decubitus ulcers. During the study pe riod, of 336 patients surveyed, 98 (29%) patients developed suspected infec tions and cultures were done; the infection rate was 4.7 per 1000 patient d ays. Of these infected patients, 59 (60%) were infected by GNBs; the infect ion rate was 2.3 per 1000 patient days. Nineteen percent of the GNB infecti ons were treated with a quinolone. (Overall. quinolones constituted about 1 7% of antibiotic usage in the SNF). Only 3 (5%) of the patients infected wi th GNB were infected with CR GNB, including Pseudomonas and Providencia spe cies. The CR GNB infections involved multiple sites, multiple organisms, an d long length of stay in the SNF. Conclusions: The Findings indicate that in this community SNF, a low freque ncy of colonization or infection with CR GNB Existed. Whether continued mod erate use of quinolones will lend to increasing levels of CR GNB will requi re further study.