Bacteremia complicating gram-negative urinary tract infections: A population-based study

Summary 

Background

Urinary tract infection (UTI) is common and bacteremia complicating this infection is frequently seen. There has been limited data published that characterize bacteremic UTI in a population-based setting over an extended period. We therefore examined the incidence rate, microbiology, outcome, and in vitro antimicrobial resistance trends of bacteremic UTI due to gram-negative bacilli in Olmsted County, Minnesota, from 1/1/1998 to 12/31/2007.

Methods

We used Kaplan–Meier method to estimate mortality rates, Cox proportional hazard regression to determine risk factors for mortality, and logistic regression to examine temporal changes in antimicrobial resistance rates.

Results

We identified 542 episodes of bacteremic gram-negative UTI among Olmsted County residents during the study period. The median age of patients was 71 years and 65.1% were females. The age-adjusted incidence rate per 100,000 person-years was 55.3 (95% confidence interval [CI]: 49.5–61.2) in females and 44.6 (95% CI: 38.1–51.1) in males. Escherichia coli was the most common pathogen (74.9%). The 28-day and 1-year all-cause mortality rates were 4.9% (95% CI: 3.0–6.8) and 15.6% (95% CI: 12.4–18.8), respectively. Older age was associated with higher mortality; community-acquired infection acquisition and E. coli UTI were both independently associated with lower mortality. During the study period, resistance rates increased linearly from 10% to 24% for trimethoprim-sulfamethoxazole and from 1% to 8% for ciprofloxacin.

Conclusions

To our knowledge, this is the first population-based study of bacteremic gram-negative UTI. The linear trend of increasing antimicrobial resistance among gram-negative isolates should be considered when empiric therapy is selected.

Keywords: Gram-negative, Bloodstream infection, Urinary tract infection, Epidemiology, Mortality, Antimicrobial resistance, Fluoroquinolones, Incidence