Wild-Type AmpC Beta-Lactamase-Producing Enterobacterales Are a Risk Factor for Empirical Treatment Failure in Patients with Bloodstream Infection.

Introduction: Beta-lactamases are frequently prescribed for Gram-negative bloodstream infections (BSIs). However, chromosomally encoded AmpC-producing Enterobacterales (AE) could overproduce beta-lactamases when exposed to third-generation cephalosporins (3GCs), with a risk of clinical failure. There are few available in vivo data on the subject. Our goal was to assess the potential role of AE as a predictive factor for clinical failure in patients with BSIs. Materials and Methods: We retrospectively analyzed patients admitted to Cannes hospital between 2021 and 2022 for BSIs due to Enterobacterales . Patient demographics, comorbidities, and main clinical and laboratory parameters during hospitalization were collected. The risk factors for clinical instability after 48 h or death, as well as for ineffective initial empirical therapy, were assessed using univariate and multivariate analyses. Results: From January 2021 to December 2022, 101 subjects were included (mean age 79 years, 60% men, 97% with comorbidities, 17% with healthcare-associated infection, 13% with septic shock, 82% with qPitt severity score < 2, 58% with urinary tract infection, and 18% with AE). Septic shock [adjusted odds ratio (OR adj ) = 5.30, 95% confidence interval (CI): 1.47-22.19, p = 0.014] and ineffective initial empirical therapy [OR adj 5.54, 95% CI: 1.95-17.01, p = 0.002] were independent predictive factors for clinical instability or death. Extended-spectrum beta-lactamases [OR adj 9.40, 95% CI: 1.70-62.14, p = 0.012], AE group [OR adj 5.89, 95% CI: 1.70-21.40, p = 0.006], and clinical instability or death [OR adj 4.71, 95% CI: 1.44-17.08, p = 0.012] were independently associated with ineffective empirical therapy. Conclusions : Infection with AE was associated with treatment failure. Empirical therapy may result in failure if restricted to 3GC.