Clinical features and outcomes of infections caused by metallo-β-lactamases producing Enterobacterales: a 3-year prospective study from an endemic area

Background: Metallo-β-lactamases (MBL)-producing Enterobacterales are increasing worldwide. Our aim was to describe clinical features, treatments and outcomes of infections by MBL-Enterobacterales.

Methods: Prospective observational study conducted in the Pisa University Hospital (Jan 2019-Oct 2022) including patients with MBL-producing Enterobacterales infections. The primary outcome measure was 30-day mortality. A multivariable Cox regression analysis was performed to identify factors associated with 30-day mortality. Adjusted hazard ratio (aHR) (95% confidence intervals, CI) were calculated.

Results: 343 patients were included: 15 VIM- and 328 NDM-producing Enterobacterales infections. Overall, 199 (58%) were bloodstream infections, 60 (17.5%) hospital-acquired/ventilator-associated pneumonias, 60 (17.5%) complicated urinary tract infections, 13 (3.8%) intra-abdominal infections, 11 (3.2%) skin and soft tissue infections. Thirty-day mortality was 29.7%. Thirty-two patients did not receive in vitro active antibiotic therapy, 215/343 (62.7%) received ceftazidime-avibactam (CZA) plus aztreonam (ATM), 33/343 (9.6%) cefiderocol-containing regimens, 26/343 (7.6%) colistin-containing regimens and 37 (10.8%) other active antibiotics. On multivariable analysis, septic shock (aHR 3.57, 95% CI 2.05-6.23, p<0.001) and age (aHR 1.05, 95% CI 1.03-1.08, p<0.001) were independently associated with 30-day mortality, while in vitro active antibiotic therapy within 48 hours from infection (aHR 0.48, 95% CI 0.26-0.8, p=0.007) and source control (aHR 0.43, 95% CI 0.26-0.72, p=0.001) were protective factors. Sensitivity analysis showed that CZA plus ATM compared to colistin was independently associated with reduced 30-day mortality (aHR 0.39, 95% CI 0.18-0.86, p=0.019). Propensity score analyses confirmed these findings.

Conclusions: MBL-CRE infections are associated with high 30-day mortality rates. Patients with MBL-producing Enterobacterales infections should received early active antibiotic therapy.