Prevalence of Nasal Carriage of Methicillin-Resistant Staphylococcus Aureus in Patients at Hospital Admission in the Netherlands, 2010 - 2017: An Observational Study

Background: The MRSA Search and Destroy strategy relies on active screening of high-risk groups. However, a substantial proportion of MRSA carriers found do not belong to the known risk groups, pointing to a reservoir of MRSA carriers in the community. Methods: We conducted an observational study to determine the prevalence of MRSA nasal carriage upon hospital admission, among patients who were screened preoperatively for nasal S. aureus carriage between 2010 and 2017. Samples of cardiothoracic patients were tested by PCR, other samples were cultured using chromogenic agar plates. A Poisson regression model with robust error variance was used to assess whether there was a trend in the prevalence of MRSA over time. Findings: In total, 31,093 nasal swabs were obtained from 25,660 patients. Three hundred seventy-five swabs (1.2%) had an invalid result . Therefore, 30,718 swabs (98.8%) were included in our analysis. Overall, S. aureus was detected in 7,981/30,718 patients (26,0% 95%CI 25.5 - 26.5%) of whom 41 were MRSA (0.13% 95%CI 0.10 - 0.18%). The MRSA prevalence varied from 0.03% to 0.17% over the years without evidence of a changing trend over time (p=0.40). Results of the questionnaire revealed that 30 of the 41 patients (73.2%) had no known risk factors for MRSA carriage (0.10%; 95% CI 0.07 - 0.14%). Interpretation: Our study revealed a sustained low prevalence of MRSA carriage upon hospital admission over 7 years. This supports the effectiveness of the Dutch Search and Destroy policy, in combination with a restrictive antibiotic prescription policy. Funding: None. Declaration of Interest: We declare no competing interests. Ethical Approval: The data used in this study were part of routine practices in The Netherlands and do not require approval from an ethics committee. The data were anonymized and analysed according to the local regulations and laws that apply for medical information.