Staphylococcus aureus harbouring Enterotoxin A as a possible risk factor for multiple sclerosis exacerbations.

Background: Staphylococcus aureus may produce superantigens that can non-specifically activate CD4(+) cells to potentially target the myelin basic protein. Objective: This study examined the association between individuals with multiple sclerosis (MS) and colonization with S. aureus harbouring superantigens. Methods: Nasal swabs were collected from non-MS subjects and patients with MS who had not experienced a relapse in the past six months (MS stable group) and who had suffered a relapse within 30 days of study recruitment (MS exacerbation group). S. aureus was isolated from the anterior nares of participants following standard procedures and staphylococcal superantigen genes (sea, seb, and tsst-1) were detected using standard laboratory PCR techniques. Results: The study enrolled 204 patients, 80 in the non-MS and MS stable groups and 44 patients in the MS exacerbation group. Overall, 27.0% of patients were colonized with S. aureus with no significant differences identified between study groups. Amongst individuals colonized with S. aureus, the prevalence of sea was significantly greater in the MS exacerbation versus non-MS study group (p<0.05; odds ratio 7.9; 95% confidence interval 1.2-49.5). Conclusions: The ability to rapidly screen patients for the presence of S. aureus producing sea may serve as a useful marker of a potential MS exacerbation.