Endocarditis infection is increasing due to staphylococcal infection

An international study reveals that infective endocarditis, infection and inflammation involving the heart valves is commonly associated with health care factors and is increasingly due to staphylococcal infection, according to a study in the June 22/29 issue of JAMA.

For decades, infective endocarditis (IE) caused by Staphylococcus aureus has been viewed primarily as a community-acquired disease, especially associated with injection drug use, according to background information in the article. Because no large, prospectively collected, and geographically diverse cohort of patients with IE existed before now, the global significance and impact of regional variations on the characteristics, treatment, and outcome of S aureus IE has not been known.

Vance G. Fowler, Jr., M.D., M.H.S., of Duke University Medical Center, Durham, N.C., and colleagues conducted a study to document the characteristics of IE caused by S aureus, including IE associated with health care contact and IE due to methicillin-resistant S aureus (MRSA), in different parts of the world; and assessed regional differences and the effect of these differences on clinical outcomes among patients with S aureus IE. The study included 1,779 patients with IE from 39 medical centers in 16 countries. The patients were enrolled in the International Collaboration on Endocarditis-Prospective Cohort Study from June 2000 to December 2003.

The researchers found that S aureus was the most common pathogen among the 1779 cases (558 patients, 31.4 percent). Health care-associated infection was the most common form of S aureus IE (218 patients, 39.1 percent), accounting for 25.9 percent (Australia/New Zealand) to 54.2 percent (Brazil) of cases. Most patients with health care-associated S aureus IE (131 patients, 60.1 percent) acquired the infection outside of the hospital. MRSA IE was more common in the United States (37.2 percent) and Brazil (37.5 percent) than in Europe/Middle East (23.7 percent) and Australia/New Zealand (15.5 percent). Patients in the United States were most likely to be hemodialysis dependent, to have diabetes, to have a presumed intravascular device source, to receive vancomycin, to be infected with MRSA, and to have persistent bacteremia.

"The finding of S aureus as the leading cause of IE differs from previous reports and may be due in part to increasing rates of staphylococcal bacteremia related to health care contact in industrialized nations," the authors write.

"S aureus is now the most common cause of IE in many areas of the developed world. Patients with IE due to S aureus exhibit distinct characteristics compared with patients with IE due to other pathogens. Health care–associated IE is emerging as the most common form of S aureus IE and has distinct features compared with more familiar forms of S aureus IE, such as community-acquired injection drug use-associated infection. MRSA is now encountered internationally as a relatively common cause of IE and is associated with persistent bacteremia. Future investigations are required to identify better treatment and prevention strategies for this serious and common consequence of medical progress," the authors conclude.