Population-based study of the epidemiology and the risk factors for Pseudomonas aeruginosa bloodstream infection

Detailed population-based data on the epidemiology of Pseudomonas aeruginosa bloodstream infections are sparse. We sought to describe the incidence rate, risk factors, and outcomes associated with P. aeruginosa bacteremia in a large Canadian health region.

A retrospective population-based surveillance for P. aeruginosa bacteremia was conducted in the Calgary Health Region (CHR, population:approx. 1.2 million) during the period from 2000 to 2006.

A total of 284 incident cases of P. aeruginosa bacteremia were identified in CHR residents, corresponding to an annual incidence rate of 3.6/100,000.Nosocomial acquisition accounted for 45% of cases,healthcare-associated community onset for 34% of cases,and community-acquired (CA) cases for 21%. Relative to the general population, risk factors for blood stream infection included male sex, increasing age, hemodialysis,solid organ transplant, diagnosis of cancer, heart disease, HIV infection, diabetes mellitus, and/or chronic obstructive airway disease (COPD). Overall mortality was 29%. Factors associated with mortality in univariate analysis included pulmonary focus of infection and co-morbidities, including chronic liver disease, substance abuse, heart disease, COPD, and cancer, and increased with the burden of co-morbidities. Despite those patients with CA disease having fewer co-morbidities,they had a significantly higher mortality rate than either healthcare-associated cases or nosocomial cases(RR 1.88, p = 0.05).

This study documents that P. aeruginosa bacteremic disease is responsible for a significant burden of illness in general populations and identifies those groups at increased risk of infection and subsequent mortality. This information can be used to identify those individuals likely to benefit from empiric anti-pseudomonal therapies.