Methods.During a 5-month period (February 1-June 30, 2004), 167 (8%) of 1,985 newly admitted general medical patients were enrolled in our study. Nasal, oropharyngeal, and rectal swab specimens were obtained at admission and every 2-3 days until hospital discharge or death. Enterobacteriaceae isolates were tested for ESBL, and Staphylococcus aureus isolates were tested for methicillin resistance.
Results.Of the 167 patients enrolled in our study, 15 (9%) were identified as nasal carriers of methicillin-resistant S. aureus (MRSA) at admission, and 13 (8%) were rectal carriers of ESBL-producing Enterobacteriaceae at admission. Univariate risk factors for rectal carriage of ESBL-producing Enterobacteriaceae included female sex (odds ratio [OR], 11 [95% confidence interval {CI}, 1.4—238]; P < .05), nursing home residence (OR, 6.9 [95% CI, 1.8-27]; P < .01), recent antibiotic treatment (OR, 9.8 [95% CI, 1.7-74]; P < .05), and concomitant nasal carriage of MRSA and/or ESBL-producing Enterobacteriaceae (OR, 5.8 [95% CI, 1.2-26]; P < .01). Multivariate risk factors were female sex and recent antibiotic treatment. During hospitalization, 35 (21%) of 167 patients had acquired rectal carriage of ESBL-producing Enterobacteriaceae (P = .002, for trend analysis). Of the 12 patients who were still in the hospital 2 weeks after admission, 4 (33%) were carriers of ESBL-producing Enterobacteriaceae. Univariate risk factors for acquisition included an age of older than 65 years (P < .005), nursing home residence (OR 2.6, [95% CI, 0.98-2.6]), impaired cognition (OR, 4.8 [95% CI, 1.9-12]), recent antibiotic treatment (OR, 2.7 [95% CI, 0.9-8.3]), respiratory assistance (OR, 4.2 [95% CI, 1.2-14]), and prolonged hospitalization. Multivariate risk factors were an age of older than 65 years and broad-spectrum antibiotic therapy.