The problem may be even more acute in hospitals. In the United States, nosocomial infections affect more than two million patients annually at a cost in excess of $4.5 billion. (7) Patients hospitalized in ICU's are up to 10 times more likely to acquire nosocomial infections than other patients are.

And the problem is not confined to North America. Results of the European Prevalence of Infection in Intensive Care Study concluded that ICU-acquired infection is common and often is associated with resistant organisms. (8) Data from that study, in which 1,417 Western European ICU's provided 10, 038 patient case reports, indicated that almost 21 percent of patients developed ICU-acquired infections, many of which were gram-positive (34 percent Enterobacteriaceae and 30 percent S. aureus; 60 percent of the S. aureus isolates were methicillin-resistant). And resistance is more prevalent in nosocomial bacterial strains than in those from the community. (9)

Three factors relate to the increased risk of nosocomial infection: intrinsic elements, such as severe underlying disease, multiple illnesses, extremes of age and immunosuppression; invasive medical devices; crowding and the presence of patients who have been colonized or infected.

Controlling nosocomial infections in the ICU has proved difficult - not only are many patients already colonized with these pathogens when admitted to the ICU, but the use of antibiotics in this environment favors the rise of resistant subpopulations. Other practices that also favor this evolution are: lapses in aseptic care during a crisis, spread on hands of personnel caring for ventilator-dependent patients whose respiratory tracts are heavily colonized or infected, and unrecognized environmental reservoirs. (9)

Nosocomial infections acquired in the ICU for which patients receive inadequate antimicrobial therapy also influence the likelihood of mortality. In one recent study, researchers found that patients who developed such infections and who also received inadequate antimicrobial therapy had a more than fourfold increased risk of death compared to patients whose infections were treated effectively. (10) Thus, the scientists recommend the early use of antimicrobial therapy for maximum efficacy, especially before sepsis and septic shock appear. They also suggest that most critically ill patients should be given empiric antimicrobial therapy when infection is first suspected.

S. aureus is the most common cause of surgical wound infections and is a leading cause of nosocomial bloodstream infections. Until the 1980's, many of these infections could be treated with methicillin and other semisynthetic penicillins. But the emergence of methicillin-resistant S. aureus (MRSA) strains led to a reliance on vancomycin as therapy for staphylococcal infection.

However, 1997 saw the emergence of S. aureus with reduced susceptibility to vancomycin. (11) Treatment for one of these patients required seven weeks of combination antimicrobial therapy and removal of a peritoneal catheter. Another patient also received prolonged antimicrobial therapy, which was complicated by kidney dysfunction that necessitated continuous ambulatory peritoneal dialysis.

Although the Centers for Disease Control and Prevention later issued specific recommendations to reduce the spread of these organisms (11), imagine how much simpler treatment would have been if physicians could have turned to an alternative agent that had a completely novel mode of action.

Next: What can be Done?