Emerging Infections in Intensive Care Units

[[author photo]]"Emerging infections" are those whose incidence in humans has been increasing over the past 2 decades or will likely increase in the near future. [1] This definition applies not only to infections that are newly discovered but also to those that have been long-recognized and are becoming more prevalent or problematic due to issues such as antimicrobial resistance. The United States and the global community are currently expending a great amount of effort and resources to study and limit the spread of many of these emerging infections.

The intensive care unit (ICU) has been an area within the hospital experiencing an impressive array of emerging infections. Factors contributing to this phenomenon include the severely ill and often immunocompromised ICU patient population and the widespread use of both broad-spectrum antibiotics and invasive devices in critically ill patients. Nosocomial ICU infections are a source of significant morbidity, mortality, and excess costs. This issue of Seminars in Respiratory and Critical Care Medicine reviews a variety of aspects of emerging ICU infections and explores options for their treatment and prevention.

The first article in this issue, coauthored by Dr. Michael Richards, the director of the Victorian Nosocomial Infection Surveillance System in Australia, defines the extent of antimicrobial resistance in ICUs and examines the differences in infection sites and rates among various types of ICUs. In addition, data are presented regarding the usual causative organisms for ICU infections, their associated antibiotic resistance profiles, and risk factors for their acquisition. The authors discuss the importance of molecular typing of organisms; such data can be extremely helpful in identifying reservoirs of organisms, particularly in outbreak settings.

Next, Drs. Dennis Maki and Christopher Crnich of the University of Wisconsin discuss line sepsis in the ICU. Dr. Maki has done extensive and widely read research on hospital-acquired infections, particularly with respect to bloodstream infections. As this article notes, intravascular device-related bloodstream infections are a common but largely preventable ICU event. The type of device, method of insertion, and care of the device all can impact infection risk, and methods for management and prevention are discussed.

Following this, a series of articles describes some of the most prevalent and deadly pathogens encountered in the ICU setting. Drs. Henry Chambers and Jose Eguia of the University of California at San Francisco discuss the epidemiology and pathogenesis of methicillin-resistant staphylococcal infections as well as treatment alternatives. Dr. Howard Gold of Beth Israel Deaconess Medical Center similarly details the problem of enterococcal infections, including infections caused by vancomycin-resistant enterococci, and Dr. John Quinn of Rush University in Chicago summarizes the important features of Pseudomonas infection in ICU patients. Dr. Jean Chastre of the Hôpital Pitié-Salpêtrière in Paris reports on the emergence of Acinetobacter as an ICU pathogen and its associated high mortality rate, particularly in ventilator-associated pneumonia.

Dr. Jan Patterson of the University of Texas Health Science Center at San Antonio explains the importance of extended-spectrum beta-lactamases (ESBLs), which have become widespread among certain organisms prevalent in ICU infections. ESBLs may be difficult to identify in the laboratory, and their presence limits treatment options. As Dr. Patterson notes, it is critical to contain the spread of organisms expressing ESBLs through infection control measures and limitation of antibiotic use.

Stenotrophononas is an additional emerging gram-negative ICU pathogen that often infects debilitated persons with underlying medical illnesses. Its manifestations and unique resistance patterns are summarized in the article by Anaissie et al from the Unviersity of Arkansas for Medical Sciences. Finally, Candida spp. are increasing in frequency as nosocomial pathogens, and this includes both C. albicans and non-albicans species. Certain non-albicans species of Candida may have intrinsic resistance to commonly used antifungals such as fluconazole and amphotericin B. The changing epidemiology of these fungal infections, their usual sites of disease, and appropriate treatments are detailed in the article by Drs. Jack Sobel and Jose Vazquez of Wayne State University.

The final two articles help summarize the problem of antimicrobial resistance among ICUs. Dr. Robert Weinstein of Cook County Hospital in Chicago stresses the importance of surveillance for drug-resistant pathogens and consistent application of the principles of infection control. Dr. Ronald Jones examines the global trends in resistance of nosocomial pathogens in ICUs using 5-year information obtained from the SENTRY database. Dr. Jones is lead investigator of the SENTRY Antimicrobial Surveillance Program that monitors trends in antimicrobial resistance among a global network of 72 medical centers. In his article, he notes the importance of using local patterns of resistance to guide empirical antimicrobial therapy in treatment of nosocomial infections.

The topics described here are ones encountered on a daily basis by practitioners caring for ICU patients. This issue of SRCCM is an excellent in-depth review of infectious ICU complications and provides a perspective on the extent of the problem of emerging ICU infections. The authors have done an outstanding job in making their articles clinically relevant and timely. We hope their contributions will aid in the management and prevention of such problems.

REFERENCE

• 1 Institute of Medicine (U.S.) Committee on Emerging Microbial Threats to Health. Emerging Infections: Microbial Threats to Health in the United States. Lederberg J, Shope R, Oaks S, eds. Washington, DC: National Academy Press; 1992.