Carbapenem-resistant Gram-negative bacilli bacteremia in Argentina (EMBARCAR): findings from a prospective, multicenter cohort study.

Background: Bloodstream infections (BSI) caused by carbapenem-resistant gram-negative bacilli (CR-GNB) are difficult-to-treat infections associated with high mortality. Outcomes of BSI due to CR-GNB may vary in different countries.

Methods: Prospective observational, multicentric study, including consecutive hospitalized index patients aged ≥18 years, with a positive blood culture for CR-GNB, between July-2020 and March-2022 in Argentina. Among patients with Klebsiella pneumoniae BSI logistic regressions adjusted by propensity score (PS) were used to identify variables associated with 30-day mortality.

Results: Overall, 466 patients with CR-GNB BSI were included. The mean age was 56.7 (SD ± 16) and most patients (75%) were in critical care units. The median INCREMENT-CPE mortality score was 10 (IQR 6-12). Most common microorganisms were K. pneumoniae (53%) and Acinetobacter baumannii (25%). Among Enterobacterales, resistance mechanisms included K. pneumoniae carbapenemase (KPC) 50%, metallo-beta-lactamase carbapenemases (MBL) 48%, OXA-carbapenemase in 6%, and combination of carbapenemases in 5% of patients. Overall, 30-day mortality was 52%.Among patients with BSI due to K. pneumoniae, the propensity score-adjusted multivariate analysis showed that an INCREMENT-CPE score of ≥8 points (OR 3.48; 95% CI 1.53, 7.93) was associated with increased 30-day mortality. In contrast, the use of regimens including ceftazidime-avibactam alone or in combination with aztreonam was associated with decreased 30-day mortality (OR 0.20; 95% CI 0.09, 0.47).

Conclusions: BSIs due to CR-GNB are associated with high mortality rates in Argentina. Among patients with CR-K. pneumoniae bacteremia the use of ceftazidime-avibactam alone or in combination with aztreonam was associated with a reduction in mortality.