Many infections tied to medical settings.

More than one-fourth of skin or muscle infections that require hospitalization originate from microbes acquired in a clinic, hospital, or other medical-care setting, researchers find.

Using data from 134 hospitals in the northeastern United States, scientists identified 7,329 cases of infection caused by no more than one microbe. The infections typically followed trauma, surgery, or an invasive medical procedure such as kidney dialysis. The researchers excluded infections of the lungs and urinary tract. Staphylococcus aureus accounted for 55 percent of all infections.

The scientists found that 27 percent of the infections arose from microbial strains acquired in hospitals. People with such infections were three times as likely to die in the hospital as were patients whose infections originated outside the medical setting, says physician Benjamin A. Lipsky of the University of Washington School of Medicine in Seattle.

People with infections acquired in medical settings "have a different prognosis" because the microbe involved is more likely to be resistant to some drugs, so doctors should treat those infections with targeted drugs rather than broad-spectrum antibiotics, Lipsky says.