Five years of nosocomial Gram-negative bacteremia in a general intensive care unit: epidemiology, antimicrobial susceptibility patterns, and outcomes

Abstract

Objectives: Nosocomial Gram-negative bacteremia in the critically ill is associated with significant morbidity and mortality. This study provides epidemiological and antimicrobial susceptibility data for nosocomial Gram-negative bacteremia in a general intensive care unit (ICU) over a five-year period.

Methods: Positive blood cultures from January 1, 1999 to December 31, 2003 were reviewed for microbial etiology and susceptibilities. Patient charts were reviewed to determine the source of infection and outcome.

Results: Forty-five nosocomial Gram-negative bacteremias occurred in 44 patients. Infection rates of 6.9/1000 admissions and 11.3/10,000 patient days remained stable. Admitting diagnoses included respiratory failure, solid organ transplant, post-surgery, and multi-trauma. Seven bacterial species were identified; Pseudomonas aeruginosa and Enterobacter spp were most common. Sources of bacteremia included pneumonia (48.9%), and central venous catheterization (22.2%). Antimicrobial susceptibilities were highest for imipenem, gentamicin, tobramycin, ceftazidime, and piperacillin-tazobactam. Ciprofloxacin susceptibility was inferior to imipenem, gentamicin, and tobramycin (p < 0.05). Mortality rates were 53.3% in the ICU, and 60% for overall hospitalization. Average length of ICU stay was 50.5 days compared to 6.13 days for all-comers.

Conclusions: Nosocomial Gram-negative bacteremia is associated with marked morbidity and mortality in critically ill patients. Significant resistance to ciprofloxacin was demonstrated. Empiric treatment regimens should be based on unit-specific data.