Epidemiology of Nosocomial Infections Due to Gram-Negative Bacilli: Aspects Relevant to Development and Use of Vaccines

Abstract

As part of an epidemiological study of nosocomial infections due to gram-negative bacilli, 5,457 such infections reported to the Center for Disease Control from eight hospitals participating in a collaborative surveillance system were analyzed to determine (1) which infections most often resulted in bacteremia or fatality, and in which patients; (2) when, during hospitalization or in relation to selected procedures, each type of infection occurred; (3) which patients were at greater risk of developing each specific gram-negative infection; and (4) whether rates of infection, bacteremia, or fatality differed by infecting organism. The results of these analyses for four sites of infection (urinary tract, lower respiratory tract, surgical wounds, and bloodstream) and six gram-negative pathogens (Escherichia coli, Proteus, Pseudomonas aeruginosa, Enterobacter, Serratia, and Klebsiella) are presented. Only minor differences among the six study strains were noted with respect to the likelihood of each genus causing specific infections, secondary bacteremia, or death. Pseudomonas and Serratia were particularly important as causes of infection in patients who were hospitalized for a long time. In conclusion, immunotherapy (with a vaccine or hyperimmune serum) effective against these six common nosocomial pathogens would probably have a major impact on morbidity and fatality due to hospital-acquired infections that are not preventable by currently available measures.