A prospective observational study of the prevalence and risk factors for colonization by antibiotic resistant bacteria in patients at admission to hospital in Singapore

Background: Drug resistant organisms pose an increasing threat to the successful treatment of common infections. Understanding colonization patterns of these bacteria is important for effective antibiotic treatment and infection control guidelines. Methods: A prospective observational study was performed to determine the prevalence of colonization with extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E), methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE) among patients admitted via the emergency department to a public tertiary hospital in Singapore. Anterior nares, groin, axillary and rectal swabs were collected at admission and cultured using standard bacteriological techniques. Clinical data including healthcare contact within the past 12 months and recent antibiotic use was collected and analyzed using a logistic regression model. Results: 1006 patients were screened. 124 (12.4%) were colonized by ESBL-E, 18 (1.8%) by MRSA while no VRE was detected. Antibiotic use within the past month was the only significant predictor for ESBL-E colonization in the regression model, with an adjusted odds ratio (AOR) of 2.58 (1.04 to 6.42). In participants recently prescribed antibiotics and hospitalized in the previous 3 months, 29.4% were colonized by ESBL-E. This represented 20.2% of the total ESBL-E burden, and ESBL-E was also detected in 6.3% of participants with no healthcare contact. Hospitalization and outpatient hospital visits predicted MRSA colonization in the univariate analysis. Neither was statistically significant in the logistic regression model, with AORs for MRSA colonization following hospitalization in the past 3 and 12 months of 3.81 [95% CI 0.84-17.28] and 3.48 [0.64-18.92] respectively. Conclusion: A high prevalence of colonization with ESBL-E was evident among patients at admission, even in the absence of recent antibiotic use or contact with healthcare.