Background: Case series have described severe lower respiratory tract infection (LRI) in healthy, community-dwelling persons caused by methicillin-resistant Staphylococcus aureus (MRSA). Evaluating populations at risk is needed.
Methods: Surveillance for patients aged 50 years or younger hospitalized with LRI who had S aureus isolated from blood or respiratory specimen during September 2008 to August 2010 was performed at 25 hospitals in 5 US metropolitan areas. Persons with recent health care exposure were excluded. Lower respiratory tract infection diagnosis required supporting radiographic or clinical evidence. Clinical characteristics of LRI were compared by methicillin resistance phenotype.
Results: In total, 94 hospitalized community-onset S aureus LRI cases were identified. Lower respiratory tract infection cases were identified in both young adults and children (60%, 35–50 years; and 19%, younger than 17 years), without any seasonality or association with influenza circulation. Among the 94 case patients with LRI, 34 patients (36%) had bacteremia, 36 patients (40%) required ICU admission, and 6 patients (6%) died; proportions were similar between cases with methicillin-susceptible S aureus and MRSA. Lower respiratory tract infection cases with MRSA had longer median length of stay compared with those with methicillin-susceptible S aureus (9 vs. 6 days; P = 0.04). Lower respiratory tract infection cases with evidence of influenza infection had higher mortality compared with LRI cases without influenza infection (31% vs. 2%; P = 0.003). During influenza circulation, 35 (55%) of 64 case patients with LRI were tested for influenza, and 9 (26%) of the 35 case patients tested positive.
Conclusions: S aureus LRI occurred in both adults and children, without any seasonality or association with MRSA and with and without evidence of influenza infection, although case fatality was higher among those with evidence of influenza infection.