Wednesday, June 29, 2005

One Consequence of Medical Progress: The Rise of Health Care-Related Infections
By Julie McKeel

The DCRI’s Dr. Vance Fowler, Dr. Chris Cabell, Dr. Ralph Corey, Dr. Kevin Anstrom, and Mr. Paul Pappas were the American co-authors for this international study.

S aureus infects the skin and mucous membranes, while infective endocarditis is an inflammation of the lining of the heart and its valves. According to the study authors, S aureus endocarditis caused by or associated with health care treatment is emerging as the most common form of infective endocarditis. Methicillin-resistant S aureus (MRSA) IE is now diagnosed in patients all over the world as a relatively common cause of IE.

The rate of S aureus infection has increased due to recent changes in health care delivery and antibiotic resistance patterns. Bacterial S aureus infections associated with health care contact have increased among inpatients and outpatients. MRSA infection rates have also increased in both hospital and clinic settings. In addition, the number of patients with implanted medical devices (e.g., prosthetic heart valves, grafts, catheters, pacemakers) has also risen over the past 20 years. This particular patient population is at high risk for S aureus bacteremia and endocarditis. While it is not clear just how these findings might influence recommended clinical practice, the authors stress that more research is critical to finding ways to identify and block these infection pathways.

Yet S aureus IE is relatively rare at any single institution. Because no large, geographically diverse group of patients with IE existed before now, the impact of regional variations on the characteristics, treatment, and outcome of S aureus IE was unknown.

In this particular observational study, patients were diagnosed with IE as defined by Duke criteria and were enrolled in the International Collaboration on Endocarditis-Prospective Cohort Study (ICE-PCS) from June 2000 to December 2003. The study included 1779 patients from 39 medical centers in 16 countries, including the United States (9 sites), South America (2 sites each from Brazil, Argentina, and Chile), Australia/New Zealand (7 sites), and Europe/Middle East (17 sites). The rate of in-hospital death was the defined primary endpoint for this study.

The researchers sought to document the characteristics of IE caused by S aureus, including IE associated with health care contact and IE due to MRSA, in different parts of the world; and to assess the regional differences among patients with S aureus IE.

During the 48-month study period of the 1779 patients with definite IE, S aureus was the most commonly identified pathogen and was present in 558 patients (31.4%).

The study confirmed that health care contact is emerging as a critical risk factor for S aureus IE. Health care-associated infection accounted for one quarter to one half of S aureus IE cases reported in the represented regions. In a large number of these patients, an intravascular device was the presumed source of bacteria. Prosthetic cardiac devices (such as pacemakers, defibrillators, and prosthetic cardiac valves) were present in almost one quarter of the patients in this study. S aureus IE was also linked with the suppression of natural immune responses which may be due to the health care for underlying diseases that are being treated with immunosuppressive drugs. The findings confirm that the development of S aureus IE is a consequence of medical progress.

The study authors emphasize that additional research is necessary to identify better treatment and prevention strategies for this unintentional but serious consequence of clinical advances. These findings underscore the need to improve infection control compliance in order to reduce the number of health care–associated infections, as well as the need for new prevention and treatment options.

According to the DCRI’s Director, Dr. Rob Califf, this study is also important because of the network of collaborators created to produce the research. "This international team gathered critical data from regions around the world, and their collaborative efforts help to establish a practical and vital research model for future investigations,” said Califf.

"In fact, this effort by Drs. Fowler and Cabell represents an approach I hope we see more of in the future at the DCRI," added Califf. "They have been dedicated to understanding an important medical problem that wasn't getting enough attention. Through their persistent efforts, their research is now receiving international attention."

The ICE Coordinating Center team at the DCRI for this study included Dr. Chris Cabell (director), Tina Harding (project leader), Dr. Kevin Anstrom, Khaula Baloch, Paul Pappas, and Judith Stafford (from Outcomes), Mary Molina (from CDI), and Lisa Clevenger and Christy Dixon.

This study was supported by the following grants from the National Institutes of Health: AI-059111 (Dr Fowler), HL-70861 (Dr Cabell), and AI-39108 (Dr Bayer); the Red Española de Investigación en Patología Infecciosa (V-2003-REDC14A-O) (Dr Miro); the Fundación Privada Máximo Soriano Jiménez (Barcelona, Spain) (Dr Miro); the Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS, Barcelona Spain) (Dr Miro); Fondo de Investigaciones Sanitarias de la Seguridad Social (FIS 00-0475) (Dr Miro); and the Ministry of Science, Republic of Croatia (0108309) (Dr Barsic).

Vance Fowler, MD

Chris Cabell, MD

Ralph Corey, MD

Kevin Anstrom, PhD

Not pictured: Paul Pappas