New epidemiology for postoperative nosocomial infections

Changes in health care delivery systems over the last decade have resulted in a major increase in outpatient surgery and a higher severity of illness for inpatients. We sought to determine the effects of this change on the epidemiology of postoperative surgical infections. Historical data on incidence and epidemiology of infection were obtained from peer-reviewed articles published between 1960 and 1999 (MEDLINE). All nosocomial infections in 5035 patients admitted to a tertiary-care university hospital surgical intensive care unit between January 1994 and December 1997 were prospectively identified and classified as wound, urinary tract, bloodstream, or pneumonia. Incidence of bacterial isolates at each site was also recorded. From these data we determined infection rates per 100 admissions. We also identified all device-related nosocomial infections and calculated infection rates. Comparisons between time periods were made. In the 1960s wound infections constituted the predominant postoperative infection at 46 per cent. This was replaced by urinary tract infection in the 1970s (44%) and 1980s (32%) and closely followed by bloodstream infections (25%). In the 1990s nosocomial pneumonia became the most common postoperative infection, comprising 43 per cent of surgical intensive care unit infections. Analysis of the bacteriology also revealed changing trends with primarily gram-positive organisms in the 1960s followed by an increase in methicillin-resistant Staphylococcus in the 1970 to 1980s, and currently resistant gram-negative bacteria predominate. The incidence of fungal infections has steadily increased. This survey identified a new epidemiology for postoperative surgical infections. Over the last several decades the reported wound infections have been markedly decreased and there is little change in urinary tract infection. Nosocomial pneumonia with resistant gram-negative bacteria now predominates along with increased incidence of fungal infections. Currently, postoperative infections are now more severe, involve critical organs, and require close monitoring of the changing patterns of pathogens.