S. aureus is an infrequent pulmonary pathogen, but it is important to detect since it is associated with severe disease and is usually resistant to standard antibiotics for CAP. Prior studies emphasized the importance of methicillin-resistant strains (MRSA) that are most common in association with influenza [77-80]. S. aureus continues to be an uncommon, but often highly lethal, cause of CAP in patients with influenza [81].
S. aureus should be suspected in patients with influenza and a bacterial superinfection, especially those with the clinical characteristics of staphylococcal toxic shock syndrome. S. aureus should also be suspected in a previously healthy young adult or child with a rapidly progressive lung infection that is often accompanied by pulmonary necrosis, shock, and neutropenia; these features have been associated with the USA 300 strain of S. aureus that causes community-acquired MRSA infection.
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