Drug-resistant staph causes more pneumonia.

Last winter, a recently discovered bacterial variant became a major cause of severe pneumonia among people who caught the flu.

Methicillin-resistant Staphylococcus aureus, or MRSA, has long been a menace in hospitals, where it can spread from one patient to another. Resistant to a class of penicillin-like antibiotics, MRSA causes difficult-to-treat pneumonias and infections of the skin, blood, and surgical sites.

In the past few years, new strains of MRSA have emerged that are not associated with health care facilities. In many U.S. cities, community-associated MRSA is now the main cause of skin infections among teams playing contact sports and in institutions, from daycare centers to jails, in which people pack closely together. However, S. aureus rarely causes pneumonia in healthy people.

To investigate reports of severe community-acquired pneumonia, researchers at the Centers for Disease Control and Prevention (CDC) in Atlanta and other institutions studied records of people who last winter developed influenza and then were hospitalized with S. aureus-caused pneumonia, The scientists studied bacteria from the patients, and found that of 17 cases, 15 involved methicillin-resistant bacteria. Genetically, the resistant bacteria matched known community strains of MRSA rather than hospital-associated strains, indicating that MRSA has become an important cause of pneumonia in otherwise-healthy people, says Jeffrey Hageman of the CDC.--B.H.