Cancer, heart, and neurologic disease are associated with significantly higher 30-day mortality from methicillin-resistant Staphylococcus aureus (MRSA), according to a study that also showed mortality rates have changed little in 9 years.

A retrospective study of 1,168 patients, who were admitted to four Michigan hospitals with MRSA over a period of 9 years, showed an overall 30-day mortality of 16% (Int J Infect Dis. 2017 May 19. doi: 10.1016/j.ijid.2017.05.010 ).

“Notably, with time, we found no improvement in overall mortality over time despite advancement in antimicrobial treatment,” wrote Pedro Ayau, MD, of the Universidad Francisco Marroquin in Guatemala City and his coauthors. “Thus far, the role of different antimicrobial agents against MRSA infection in clinical settings is uncertain.”

Patients with cancer showed the highest 30-day mortality risk from MRSA infection (odds ratio, 2.29; P = .001). Heart disease increased the mortality risk by 78%, neurologic disease by 65%, and nursing home residence by 66%. A Charlson index score greater than 3 was associated with an 88% increase in 30-day mortality.

Age was also an independent risk factor, with each additional year of age associated with a 2.9% increase in the odds of 30-day mortality, even after accounting for other variables.

The authors found evidence of a protective effect associated with diabetes and peripheral vascular disease, with a decrease in 30-day mortality of 40% and 47%, respectively. Although this was an unexpected finding, it was likely related to the source of the infection, they said.

“Patients with [peripheral vascular disease] and diabetes are usually less acutely ill and present with skin/wound infections, which are more easily managed, and started earlier on appropriate antibiotic treatment,” the investigators wrote.

Patients who were readmitted had an 88% lower risk of 30-day mortality. The authors suggested this may be because these patients would likely have received earlier and better management of the infection.

There was also a relationship between the source of infection and mortality. Patients infected from an indwelling central venous catheter had a 61% lower 30-day mortality. Those with skin or wound infections had a 52% lower mortality, and those with genitourinary infection had a 60% lower mortality.

In contrast to other studies, the researchers did not see any significant increase in 30-day mortality with persistent bacteremia.

Two authors declared research grants from the pharmaceutical industries.