Epidemiology and Risk Factors Associated With Mortality in Consecutive Patients With Bacterial Bloodstream Infection: Impact of MDR and XDR Bacteria

Background: Mortality related to bloodstream infections (BSIs) is high. The epidemiology of BSIs is changing due to the increase in multidrug resistance, and it is unclear whether the presence of multidrug-resistant (MDR) organisms, per se, is an independent risk factor for mortality. Our objectives were, first, to describe the epidemiology and outcome of BSIs and, second, to determine the risk factors associated with mortality among patients with BSI.

Methods: This research used a single-center retrospective observational study design. Patients were identified through microbiological reports. Data on medical history, clinical condition, bacteria, antimicrobial therapy, and mortality were collected. The primary outcome was crude mortality at 30 days. The relationships between mortality and demographic, clinical, and microbiological variables were analyzed by multivariate analysis.

Results: A total of 1049 inpatients were included. MDR bacteria were isolated in 27.83% of patients, where 2.14% corresponded to an extremely drug-resistant (XDR) isolate. The crude mortality rates at days 7, 30, and 90 were 12.11%, 25.17%, and 36.13%, respectively. Pitt score >2, lung and abdomen as site of infection, and XDR Pseudomonas aeruginosa were independent risk factors for 7-, 30-, and 90-day mortality. Charlson score >4, carbapenem-resistant Klebsiella pneumoniae, and XDR Acinetobacter baumannii were independent risk factors for 30- and 90-day mortality. Infection by XDR gram-negative bacteria, Charlson score >4, and immunosuppression were independent risk factors for mortality in patients who were stable at the time of BSI.

Conclusions: BSI is an event with an extreme impact on mortality. Patients with severe clinical condition are at higher risk of death. The presence of XDR gram-negative bacteria in blood is strongly and independently associated with patient death.