MRSA associated with worse survival in patients with cystic fibrosis

Presence of methicillin-resistant Staphylococcus aureus (MRSA) in the respiratory tract is associated with worse survival in patients with cystic fibrosis, a new study has shown.

Researchers performed a cohort study of patients with cystic fibrosis seen at U.S. Cystic Fibrosis Foundation-accredited centers from January 1996 to December 2006. Patients were 6 to 45 years of age at study entry and were followed until December 2008. Data were obtained from the Cystic Fibrosis Foundation Patient Registry, which began specifically collecting information on the presence or absence of respiratory-tract MRSA in 1996. The main outcome measure was time from age at study entry to age at death from any cause. Study results appeared in the June 16 Journal of the American Medical Association.

Overall, 19,833 patients were included, accounting for 137,819 patient-years of observation (median, 7.3 years per patient). During this time, 2,537 patients died and 5,759 were found to have respiratory-tract MRSA. Patients with MRSA had a higher mortality rate (27.7 deaths per 1,000 patient-years; 95% CI, 25.3 to 30.4) than those without (18.3 deaths per 1,000 patient-years; 95% CI, 17.5 to 19.1), and a 34.0% (95% CI, 26.7% to 40.4%) attributable risk percentage of death associated with MRSA. MRSA was associated with a higher risk for death in unadjusted analysis (hazard ratio, 1.47; 95% CI, 1.32 to 1.62) and after adjustment for illness severity (hazard ratio, 1.27; 95% CI, 1.11 to 1.45). The median estimated age of survival was higher in the non-MRSA group than in the MRSA group (36.9 years vs. 30.7 years).

The authors noted that their study had several important potential limitations, including misclassification of patients, sampling bias, and lack of analysis of whether MRSA treatment would have affected outcome. However, they concluded that patients with cystic fibrosis and respiratory-tract MRSA are at greater risk for death than cystic fibrosis patients without MRSA. Their study, taken together with previous data, "further establish MRSA as a significant CF pathogen and provide impetus for more aggressive treatment of CF patients who are persistently MRSA positive," they wrote. They also noted the need to emphasize infection control guidelines in patients with cystic fibrosis to minimize MRSA transmission.