Staphylococcal nasal colonisation amongst medical students

Abstract

Background: Staphylococcus aureus is a common cause of hospital-acquired infections. Medical undergraduates are frequently exposed to hospital-adapted bacterial strains especially S. aureus and therefore are always at risk of colonisation. Materials and Methods: A prospective study was conducted on 150 undergraduate students, of different semesters, to detect S. aureus nasal colonisation. A detailed history regarding attending the hospital ward teaching, hospitalisation, frequency of nose touching and immunocompromised condition was unequivocally obtained from all the participants. Anterior nares were swabbed and inoculated on mannitol salt and blood agar plates. S. aureus isolates were subsequently verified by conventional microbiological techniques. The antibiotic susceptibility testing was done by the modified Kirby–Bauer disc diffusion method. In addition, PCR-based detection of mecA gene and pvl gene was performed. Results: Out of 150 students, we found 18 students (3 of 1st, 10 of 5th and 5 of 9th semester, respectively) to be colonised by S. aureus. Of these 18 isolates, 8 were found to be methicillin-resistant. We observed a significant association (P < 0.05) of hospital exposure, ward teaching/hospitalisation with S. aureus colonisation. These S. aureus isolates exhibited varying susceptibility towards different antibiotics with multiple antibiotic resistance indexes ranging from 0.08 to 0.58. Interestingly, all eight methicillin-resistant S. aureus isolates displayed mecA positivity while all were found to be pvl negative. Conclusion: The results indicate the importance of imparting knowledge about infection control practices during the initial years of undergraduate training in medical schools, which may increase awareness amongst students before getting outpatient or ward postings.