Prevalence of methicillin-resistant staphylococcus epidermidis in new hospital residents: A cohort study of new resident physicians in a university-affiliated hospital

Methicillin-resistant Staphylococcus epidermidis (MRSE) is known to cause various nosocomial infections. However, there is limited data available regarding its prevalence, especially among the cohorts of new resident physicians. Our aim in this study was to describe the carriage rate of MRSE in the anterior nares of new resident physicians in the hospital over a 12-month period. We used a prospective cohort design that examined the relationship between duration of work and the MRSE carriage rate. The volunteer participants consisted of 64 new resident physicians working full time in the hospital with no previous work experience and without anterior nares infections. Of the 64 participants, 45 completed the data collection at 12 months. Nasal swabs were obtained from the residents at 0, 6, and 12 months, yielding a total of 517 strains. All S. epidermidis strains were examined for the minimum inhibitory concentration (MIC). For MRSE strains, staphylococcal cassette chromosome mec (SCCmec) typing was performed. Strains that were only resistant to oxacillin were analyzed using multilocus variable-number tandem repeat analysis (MLVA) for genetic testing. MRSE prevalence was 56.2％, 70.6％, and 82.2％ at 0, 6, and 12 months, respectively. Data related to the drug-resistance profile and SCCmec type revealed a possible dominant strain among the isolated MRSE strains. Moreover, the prevalence of MRSE increased over time, and MLVA analysis verified that there was a dominant strain among the isolated MRSE strains. In addition, the duration of work directly correlated with the MRSE carriage rate, suggesting that the duration of the work is related to MRSE acquisition.