Longitudinal Assessment of Colonization With Staphylococcus aureus in Healthy Collegiate Athletes

Background. Staphylococcus aureus is the leading cause of skin and soft tissue infections in the United States, and S. aureus colonization increases the risk of infection. Although athletes have a higher risk of infection with S. aureus than the general population, most studies in athletes have not assessed colonization. Methods. We conducted a prospective cohort study of Vanderbilt University varsity athletes from August 2008 to April 2010. We assessed nasal and oropharyngeal colonization with methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains by obtaining swabs at enrollment and monthly thereafter until the end of the study. The athletes were also monitored for skin and soft tissue infections. Results. We enrolled 377 athletes and trainers (224 in contact sports and 153 in noncontact sports). The total S. aureus colonization prevalence ranged from 34% to 62%, and for MRSA it ranged from 8% to 29%. The colonization rate in the summer was significantly higher than that in the winter (odds ratio for MRSA [ORMRSA], 1.70 [95% confidence interval (CI), 1.23-2.35]; ORMSSA, 1.38 [95% CI, 1.05-1.82]). Of 603 MRSA isolates, 75% carried the staphylococcal cassette chromosome mec (SCCmec) type IV, and 5% carried the genes encoding Panton-Valentine leukocidin. Nine symptomatic S. aureus infections occurred, 7 of which were between July and September. Conclusions. The S. aureus colonization rate is higher than previously reported and fluctuated over time in this prospective cohort of athletes. The higher colonization prevalence during summer might explain the infectious outbreak during the summer months and may represent a key intervention time for preventing S. aureus disease in athletes.