Are infections due to resistant pathogens associated with a worse outcome in critically ill patients?

OBJECTIVES: To evaluate the outcome of critically ill patients infected with antimicrobial resistant microorganisms, and to analyse the factors involved in the development of antimicrobial resistance.

METHODS: All patients admitted to a 31-bed mixed medico-surgical intensive care unit who developed a nosocomial infection were prospectively followed until discharge or death.

RESULTS: Of 949 consecutive patients admitted, 186 developed a nosocomial infection: 79 with an antimicrobial-resistant pathogen and 107 with susceptible strains. The lungs were the main source of infections in both groups. The main resistant microorganisms were Enterobacter aerogenes, methicillin resistant Staphylococcus aureus (MRSA), and Enterobacter cloacae. The main susceptible microorganisms were Enterobacter spp., methicillin susceptible S. aureus (MSSA), and Proteus mirabilis. Patients infected with resistant strains had a longer length of stay prior to infection (9+/-4 vs. 5+/-3 days), longer total length of stay (18+/-16 vs. 11+/-7 days), longer duration of mechanical ventilation (12+/-15 vs. 6+/-7 days), and more severe coagulation, liver, and renal dysfunction (all p<0.05). The maximum degrees of organ failure during the ICU stay, and the respiratory dysfunction, but not infection with a resistant pathogen, were independent predictors for death. Multivariate logistic regression revealed previous use of multiple antibiotics, duration of length of stay prior to infection, and the degree of liver failure as independent factors for development of infection with resistant organisms.

CONCLUSIONS: Infection with antimicrobial resistant microorganisms is not an independent predictor for death. The development of antimicrobial resistance is related to the previous use of multiple antibiotics, the ICU length of stay, and the severity of hepatic dysfunction.