Prevalence and antimicrobial susceptibility of Staphylococcus aureus methicilin resistant isolated from medical students

Objective: To establish the prevalence and identify the level of resistance to methicillin, vancomycin and alternative antibiotics in Staphylococcus aureus isolates from medical students in clinical training. Materials and methods: A cross-sectional observational design with non-random sampling was used in medical students during clinical training in a tertiary healthcare facility. Samples were taken from nasal and hands swabs and cultured on blood agar. For beta-hemolytic gram-positive cocci, catalase and coagulase tests were performed and then cultured on mannitol salt agar. Susceptibility to cefoxitin, oxacillin, linezolid, clindamycin and trimethoprim sulfamethoxazole was assessed by using the Kirby-Bauer technique, and for vancomycin, an E-test was performed (Biomerieux®). Results: 72 strains of S. aureus were isolated from 82 medical students. 72.2 % were identified as methicillin-sensitive (MSSA) and 27.8 % as methicillin-resistant (MRSA). Four MRSA strains (20 %) showed vancomycin intermediate (VISA 4-8 µg/mL) profile, 65 % of MRSA isolates was resistant to clindamycin, 40 % to linezolid and 45 % to trimethoprim sulfamethoxazole. Conclusions: MSSA, MRSA and VISA strains are present in nostrils and hands of our medical students, with MRSA showing high resistance levels to clindamycin, TMP-SMX and linezolid, and MSSA levels up to 45 %. These findings reiterate the need to accomplish good hands hygiene in order to minimize the spread of S. aureus in community and healthcare facilities.