Two-year prospective evaluation of colonization with extended-spectrum beta-lactamase-producing Enterobacteriaceae: time course and risk factors.

BACKGROUND: We wanted to determine the time course of colonization with extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae (EPE), sites of colonization and risk factors for prolonged colonization with EPE to obtain information for successful infection control measures. METHODS: Rectal swab, urine, throat swab and other clinically relevant samples (wound swab, tracheal aspirate and sputum) were obtained from each participant. Sets of follow-up samples and data about potential risk factors for prolonged colonization with EPE were collected every 3 months for 2 years. Multivariate analysis using a logistic regression model was performed to identify risk factors for prolonged colonization. RESULTS: A total of 114 patients were included in the study, 49 completed the 2-year follow-up. In all, 611 sample sets were collected, 309 (50.6%) of which were positive for ESBL. Of the positive sample sets, 90% had a rectal swab positive for ESBL, the throat swab was positive for ESBL in 17.2% of cases and urine in 36.2% of cases; 10% of positive sample sets had negative rectal swabs with EPE isolated from other sites, most often from urine. Immobility was found to be associated with prolonged carriage (≥ 12 months) of EPE. After 2 years, 15/49 (30.6%) patients were colonized with EPE. In 12/49 (24.5%) patients, transient negativity was observed. CONCLUSIONS: We found that prolonged colonization with EPE was common, especially in bedridden patients. Transient negative samples were often observed during the course of colonization. In some patients, urine can be the only positive site from which EPE are isolated.