Predictors of in-hospital mortality for bloodstream infections caused by Enterobacter species or Citrobacter freundii

Study Objective. To identify predictors of in-hospital mortality among patients with bacteremia caused by Enterobacter cloacae, Enterobacter aerogenes, or Citrobacter freundii. Design. Retrospective cohort study. Setting. 1300-bed tertiary academic medical center. Patients. One hundred twenty-four patients who had bloodstream infections caused by E. cloacae (3), E. aerogenes (71), or C. freundii (50) between 1998 and 2004. Measurements and Main Results. Data from patients with bloodstream infections caused by Enterobacter sp or C. freundii were retrospectively segregated according to hospital survival (98 survivors, 26 nonsurvivors). Multiple patient characteristics and processes of care were evaluated to identify factors contributing to in-hospital mortality. Multiple logistic regression was performed based on univariate comparisons to determine independent risk factors for in-hospital mortality. Among the 124 cases of bacteremia, the crude in-hospital mortality rate was 21% (26 cases). Univariate analysis revealed that survivors were more likely to receive an aminoglycoside as part of their empiric antimicrobial regimen (40% [39/98]) compared with nonsurvivors (19% [5/26], p=0.05). Other factors related to antimicrobial therapy including choice and number of agents used did not differ between survivors and nonsurvivors (p>0.05). Vasopressor use (31% [30/98] vs 62% [16/26]), care in an intensive care unit (19% [19/98] vs 54% [14/26]), and acute renal failure (13% [13/98] vs 31% [8/26]) occurred more frequently in nonsurvivors (p<0.05). Multiple logistic regression identified resistance to second- or third-generation cephalosporins (adjusted odds ratio [OR] 5.16, 95% confidence interval [CI] 2.66-10.0, p=0.013), trimethoprim-sulfamethoxazole resistance (adjusted OR 5.44, 95% CI 2.53-11.7, p=0.027), and mechanical ventilation (adjusted OR 12.2, 95% CI 5.99-24.5, p<0.001) as independent determinants of mortality. Conclusion. Among patients with Enterobacter sp or C. freundii bloodstream infections, those with trimethoprim-sulfamethoxazole- resistant or second-or third-generation cephalosporin-resistant strains or those who required mechanical ventilation had an increased risk of mortality.