Nasal carriage and antimicrobial susceptibility of Staphylococcus aureus among medical students at the HRH Princess Maha Chakri Sirindhorn Medical Center, Thailand: a follow-up study.

OBJECTIVE: The objective of this study is to evaluate the patterns of nasal colonization of Staphylococcus aureus and its susceptibility patterns among medical students before and after their rotations in the hospital. METHODS: Nasal swabs were obtained from 128 medical students for microbiological study and susceptibility testing prior to working in the hospital (the first), following the first rotation (the second) and at the end of the rotation schedule in the hospital (the last). The probable risk factors for nasal carriage were recorded for assessment. RESULTS: S. aureus was isolated at the first, second and last swabs with colonization rates of 29.7%, 30.5% and 39.4%, respectively. The prevalence rate of colonization of S. aureus showed a statistically significant increase (P<0.05). There was a persistent colonization of S. aureus at the rate of 20.3%. No participants showed methicillin-resistant S. aureus. The susceptibility of S. aureus to erythromycin and clindamycin was 36.8%, 41% and 34% at the first, second and last swabs, respectively. There was no significant correlation between nasal carriage of S. aureus and its potential risk factors. CONCLUSIONS: After clinical rotation in the hospital, the prevalence rate of asymptomatic nasal carriage of S. aureus increased and the S. aureus isolated has shown a relatively high resistance to erythromycin and clindamycin.

Nasal carriage and antimicrobial susceptibility of Staphylococcus aureus among medical students at the HRH Princess Maha Chakri Sirindhorn Medical Center, Thailand: a cross sectional study.

OBJECTIVE: To determine the epidemiology of the nasal carriage of Staphylococcus aureus and its susceptibility pattern among preclinical medical students at the HRH Princess Maha Chakri Sirindhorn Medical Center, Srinakharinwirot University. METHODS: Nasal swabs were taken from 128 preclinical medical students prior to working at the hospital. Susceptibility testing of S. aureus was performed using Kirby Bauer's disc diffusion method. RESULTS: Of the 128 participants, 38/128 (29.7%; 95% confidence interval [CI]=21.8%, 37.6%) were carriers of S. aureus. No methicillin-resistant S. aureus was detected by the cefoxitin disk diffusion test. Resistance of S. aureus to erythromycin, clindamycin, tetracycline, chloramphenicol and fusidic acid was observed at the following rates: 63.2% (95% CI; 47.8%, 78.5%), 63.2% (95% CI; 47.8%, 78.5%), 34.2% (95% CI; 19.1%, 49.3%), 2.6% (95% CI; -2.5%, 7.7%) and 2.6% (95% CI; -2.5%, 7.7%), respectively. There was no statistically significant correlation between nasal carriage of S. aureus and possible risk factors. CONCLUSIONS: The prevalence of asymptomatic nasal carriage of S. aureus was higher than reported by previous literature in Thailand, and S. aureus isolates exhibited relatively high resistance to erythromycin and clindamycin.