Carriage of antimicrobial-resistant commensal bacteria in Dutch long-term-care facilities

The objective of this study was to assess carriage of antimicrobial-resistant commensal microorganisms, i.e. Escherichia coli and Staphylococcus aureus, and its predictors in long-term-care facilities (LTCFs). Nasal swabs and/or urine or incontinence samples were collected from participating residents in 111 LTCFs and tested for the presence of S. aureus and/or E. coli, respectively. Antimicrobial resistance to eight antimicrobials was linked to antimicrobial usage in the year preceding sampling and to LTCF characteristics. Using multilevel logistic regression, predictors of carriage of ESBL-producing E. coli in LTCFs were identified. S. aureus was identified in 1269/4763 (26.6%) nasal swabs, including 13/4763 (0.3%) MRSA carriers in 9/107 (8%) LTCFs. Of the 5359 urine/incontinence samples, 2934 (55%) yielded E. coli, including 123 (4.2%) producing ESBL, which were found in 53/107 locations (range 1%-33%). For all but one antimicrobial (i.e. nitrofurantoin) >20% of isolated E. coli were resistant. Multilevel multivariable logistic regression identified two predictors of carriage of ESBL-producing E. coli: (i) antimicrobial usage (OR 1.8, 95% CI 1.1-3.0 for each extra 50 DDD/1000 residents/day); and (ii) presence of MRSA carriers in the LTCFs (OR 2.4, 95% CI 1.0-5.6). The low proportion of 4.2% ESBL-producing E. coli and the low prevalence of 0.3% MRSA carriage found in LTCF residents suggest that Dutch LTCFs are not yet an important reservoir of MDR potential pathogens. Nevertheless, the large variation between LTCFs warrants close monitoring of antimicrobial resistance in LTCFs. Integrated surveillance, i.e. linking data sources on antimicrobial usage, microbiological testing, clinical background data and epidemiological data, is needed.