The microbiology of multiple organ failure. The proximal gastrointestinal tract as an occult reservoir of pathogens.

The microbiology of infection acquired in the intensive care unit (ICU) was studied prospectively in 205 consecutive patients admitted to a surgical intensive care unit. A multiple organ failure (MOF) score was calculated for each admission. Susceptibility to ICU-acquired infection increased with increasing MOF scores. While Escherichia coli, Bacteroides fragilis, and enterococci were the most common isolates from infections present at the time of ICU admission, Staphylococcus epidermidis, Candida, and Pseudomonas dominated infections occurring in patients with high MOF scores. Mortality correlated highly with infection due to S epidermidis or Candida and only poorly with infection due to Pseudomonas or E coli; significant foci of invasive infection were frequently absent at autopsy. Quantitative cultures of proximal gastrointestinal fluid in 16 of these patients showed Candida, S epidermidis, and Pseudomonas to be the most common isolates, and all but one patient colonized with these organisms had invasive infection with the same organism. The proximal gastrointestinal tract appears to be an important occult reservoir of the predominant pathogens in MOF.