Efficacy of ceftazidime-avibactam plus aztreonam in patients with bloodstream infections caused by MBL- producing Enterobacterales.

BACKGROUND: In vitro data support the use of combination of aztreonam (ATM) with ceftazidime-avibactam (CAZ-AVI), but clinical studies are lacking. The aim of our study was to compare the outcome of patients with bloodstream infections (BSIs) due to MBLs-producing Enterobacterales treated either with CAZ-AVI plus ATM or other active antibiotics (OAAs). METHODS: Prospective observational study including patients admitted to three hospitals in Italy and Greece. The primary outcome measure was the 30-day all-cause mortality. Secondary outcomes were clinical failure at day 14 and length of stay (LOS) after BSI diagnosis. Cox regression analysis including a propensity score (PS) for receiving CAZ-AVI plus ATM was performed to evaluate primary and secondary outcomes. A PS-based matched analysis was also performed. RESULTS: We enrolled 102 pts with BSI, 82 had infections caused by NDM-producing (79 K.pneumoniae and 3 E.coli) and 20 by VIM-producing (14 K.pneumoniae, 5 Enterobacter spp, 1 M.morganii) strains. The 30-day mortality rate was 19.2% in CAZ-AVI/ATM group vs 44% in OAAs group (p=0.007). The PS-adjusted analysis showed that the use of CAZ-AVI/ATM was associated with lower 30-day mortality (HR 0.37, 95% CI 0.13-0.74, p=0.01), lower clinical failure at day 14 (HR 0.30, 95% CI 0.14-0.65, p=0.002) and shorter LOS (sHR 0.49, 95% CI 0.30-0.82, p=0.007). The PS-matched analysis confirmed these findings. CONCLUSIONS: CAZ-AVI/ATM combination offers therapeutic advantage compared to OAAs for patients with BSI due to MBL-producing Enterobacterales. Further studies are warranted.