Clinical, Microbiology Reviews, oct. 1993;6(4):428-42
Autores:

T. Grace Emori
Robert P. Gaynes
Hospital Infections Program, National Center for Infectious Diseases
Centers for Disease Control and Prevention
Atlanta, Georgia

Introducción: Scope and magnitude of the problem

Nosocomial infections are a major source of morbidity and mortality, affecting more than 2 million patients annually in the United States (64). In the most comprehensive study on nosocomial infections to date, 5.7% of the 169,526 patients in 338 randomly selected U.S. hospitals developed a nosocomial
infection (63). The annual economic burden of nosocomial infections in the United States is estimated to be more than $4.5 billion in 1992 dollars (97). The extra days, extra charges, and deaths attributed to nosocomial infections vary by infection site, but together, the adverse consequences of nosocomial infections and their associated costs are substantial (Table 1).

Hospitalized patients are at unusually high risk of infection for various reasons. They tend to be more susceptible to infection because of their underlying disease conditions, but their risk is compounded when they are exposed to certain invasive procedures. If the patient is immunocompromised,
microorganisms that are not normally pathogenic are capable of causing disease. Furthermore, the hospital environment supports the acquisition of resistance to antibiotic agents by pathogens, complicating the treatment of infections due to drug-resistant pathogens.

In this review, we will use data from the National Nosocomial Infections Surveillance (NNIS) system, which is conducted by the Centers for Disease Control and Prevention (CDC), and data published by others to describe the
epidemiology of nosocomial infections, including the sites of infection, etiologic agents, and antimicrobial agent resistance. The NNIS system is the only source of national data on nosocomial infections and currently consists of 149 hospitals that voluntarily report to CDC their nosocomial infection data, which are collected under standard surveillance protocols and infection definitions (37, 48, 70).

We will focus on endemic infections, i.e., those that occur in an ongoing fashion, rather than epidemic infections, i.e., those that occur in outbreaks, since epidemic infections are estimated to represent only 5% of all nosocomial infections (132). We will discuss current approaches to infection control,
particularly those that pertain to patients who are at highest risk of infection, and the essential role of the microbiology laboratory in infection control. We will not discuss in detail the infection control measures used to
protect workers in the hospital or laboratory from the risk of infection.
Emori, T. Grace; Gaynes, Robert P.