Nasal colonization by methicillin-sensitive and methicillin-resistant Staphylococcus aureus among medical students

Nasal carriers of methicillin-resistant Staphylococcus aureus (MRSA) are common and play an important role in nosocomial infections. The prevalence rate and characterization of nasal carriers of MRSA among medical students in Jordan has not been investigated before.

The resistance of S. aureus to several antibiotics was tested using disc diffusion method, automatic Vitek 2, and penicillin binding protein (PBP) 2 slide test. Bacterial species and resistance genes were confirmed using molecular analysis of three relevant genes by real-time PCR. Two hundred ninety nasal swabs were collected from medical students at Hashemite University from June 2015 to August 2016. All participants signed a voluntary consent form and filled a predesigned questionnaire.

The mean age of participants was 19.7 ± 2 years and 61.7% of them were males. 63 out of the 290 (21.7%) samples were identified to have S. aureus, 56 (19.3%) were methicillin-sensitive S. aureus (MSSA) and 7 (2.4%) were MRSA. S. aureus nasal colonization significantly associates with male gender (OR = 1.7, CI = 0.94-3.18, P = 0.049) and chronic illnesses (OR = 4.0, CI = 1.52-10.65, P = 0.006). Consistency between disc diffusion, Vitek 2, and PBP 2 methods for MRSA screening were satisfactory compared to molecular analysis. All MRSA samples were positive for SCCmec:orfx junction gene (MRSA-specific), nuc gene (S. aureus- specific), mecA gene (PBP-mediated resistant), and PBP2 production. All MRSA isolates were multi-drug resistant and were sensitive to Linezolid, Vancomycin, and Tigecycline.

This study confirms that nasal colonization by MRSA among medical students necessitates further attention to prevent nosocomial infections.