Cumulative Incidence of Methicillin-Resistant Staphylococcus aureus Colonization in Resident Physicians Over Time

Background Methicillin-resistant Staphylococcus aureus (MRSA) can colonize up to 14.5% of healthcare workers (HCWs). The colonization rate of HCWs or the hospital setting that contributes most to MRSA colonization is less clear. In this study, we studied new resident physicians (PGY-1), as a model for HCWs, to measure their colonization rate and hypothesized that the incidence of colonization would increase during their first year. Methodology We prospectively enrolled PGY-1 residents of multiple specialties at three academic medical centers. After obtaining informed consent, PGY-1 residents were tested for MRSA in June 2019 before starting any clinical rotations and then retested every three to four months thereafter. The coronavirus disease 2019 pandemic forced us to end the study early. If MRSA-positive, residents were treated with 2% mupirocin and retested for a cure. For comparison, upper-level residents (PGY-2-5) were also enrolled to obtain a baseline prevalence of colonization. Results We enrolled 80 PGY-1 and 81 PGY-2-5 residents in the study. The baseline prevalence of MRSA colonization was 4.94% (4/81) in PGY-2-5 residents and 2.50% (2/80) for new PGY-1 residents; however, this was not statistically significant (p = 0.68). The cumulative yearly incidence of developing MRSA colonization in PGY-1 residents was 4.51%. MRSA colonization was successfully treated in 75% of cases. Conclusions PGY-1 residents had a lower MRSA colonization rate compared to PGY-2-5 residents, although this was not statistically significant. PGY-1 residents had a small incidence of developing MRSA colonization while working in the hospital. Further research is needed to determine if this is clinically relevant to HCWs or their patients.