Risk Factors for Infection of Staphylococcus aureus: Nasal Carriage, Skin Carriage and Multi-antibiotic Resistance in Healthy Individuals

Aims: The study investigated the nasal and skin carriage of Staphylococcus aureus in healthy individuals and the antibiotic resistance profile.

Study Design: A descriptive laboratory based surveillance study.

Place and Duration of Study: Department of Biological Sciences, Ondo State University of Science and Technology, Okitipupa, between May and November 2016.

Methodology: Eighty samples were obtained from anterior nares and skin of 40 healthy volunteers aged 19 to 35 years. Isolates were identified by cultural characteristics on Mannitol Salt Agar, biochemical tests. Percentage carriage of S. aureus was calculated separately for nasal and skin samples. Antibiotic susceptibility testing was performed by the disk diffusion method to determine the multi-antibiotic resistance (MAR) profile.

Results: From 40 nasal samples, 17 (42.5%) yielded S. aureus from 12 (30.0%) female and 5 (12.5%) male volunteers. Out of 40 skin samples, 17 (42.5%) samples yielded S. aureus from 8 (20.0%) female and 9 (22.5%) male volunteers. There were no differences in the number/percentage of nasal and skin samples yielding S. aureus; but there were differences in the number/percentage of nasal samples of male and female volunteers colonized by S. aureus, while little difference was found in the number/percentage of skin samples of male and female volunteers colonized by S. aureus. MAR for nasal isolates was 66.7% to 77.8%, and for skin isolates 66.7% to 88.9%. The isolates showed 100% resistance to six antibiotics; but zero resistance to ofloxacin. MAR index for nasal and skin isolates ranged from 0.67 to 0.89.

Conclusion: S. aureus carriage of 42.5% in the nasal cavity and skin, combined with high MAR index of 0.67 to 0.89 are serious risk factors for infection when the immune system is compromised. Nasal decolonization, proper hand washing, use of hand gloves and appropriate use of antibiotics will reduce the risk of S. aureus colonization, transfer and infection, and the consequent high morbidity and mortality.