Prospective Evaluation of Colonization with Extended-Spectrum β-Lactamase (ESBL)–Producing Enterobacteriaceae Among Patients at Hospital Admission and of Subsequent Colonization with ESBL-Producing Enterobacteriaceae Among Patients During Hospitalization

Abstract

Objective.: To determine the rates of and risk factors for carriage and acquisition of extended-spectrum (β-lactamase (ESBL)-producing Enterobacteriaceae during hospitalization.Design.: Cohort study.Setting.: Shaare Zedek Medical Center, a 550-bed teaching hospital.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, andStaphylococcus aureusisolates were tested for methicillin resistance.Results.: Of the 167 patients enrolled in our study, 15 (9%) were identified as nasal carriers of methicillin-resistantS. 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.Conclusions.: Rectal carriage of ESBL-producing Enterobacteriaceae occurred in 13 (8%) of 167 patients at admission to the medical departments of our hospital and in 4 (33%) of 12 patients still remaining in our hospital after 2 weeks.