To elucidate new risk factors for MRSA carriers without known risk factors (MRSA of unknown origin; MUO). These MUO carriers are neither pre-emptively screened nor isolated as normally dictated by the Dutch Search & Destroy policy, thus resulting in policy failure.
We performed a prospective case control study to determine risk factors for MUO acquisition/carriage (Dutch Trial Register: NTR2041).
Cases were MUO carriers reported by participating medical microbiological laboratories to the RIVM from September 1 st 2011 until September 1 st 2013. Controls were randomly selected from the community during this period.
Significant risk factors for MUO in logistic multivariate analysis were antibiotic use in the last twelve months, aOR 8.1 (5.6 - 11.7), screened as contact in a contact tracing but not detected as a MRSA carrier at that time, aOR 4.3 (2.1 - 8.8), having at least one foreign parent, aOR 2.4 (1.4 - 3.9) and receiving ambulatory care, aOR 2.3 (1.4 - 3.7). Our found risk factors explained 83% of the MUO carriage.
Identifying new risk factors for MRSA carriers remains crucial for countries that apply a targeted screening approach as a Search and Destroy policy or as vertical infection prevention measure.