Treatment of Bacteremia Caused by Enterobacter spp. Should the Potential for AmpC Induction Dictate Therapy? A Retrospective Study

Objective: Carbapenems are considered treatment of choice for bacteremia caused by potential AmpC-producing bacteria, including Enterobacter spp. We aimed to compare mortality following carbapenem vs. alternative antibiotics for the treatment of Enterobacter spp. bacteremia. Patients and Methods: We conducted a retrospective study in two centers in Israel. We included hospitalized patients with Enterobacter bacteremia treated with third-generation cephalosporins (3GC), piperacillin/tazobactam, quinolones, or carbapenem monotherapy as the main antibiotic in the first week of treatment, between 2010 and 2017. Cefepime was excluded due to nonavailability during study years. The primary outcome was 30-day all-cause mortality. Univariate and multivariate analyses were conducted, introducing the main antibiotic as an independent variable. Results: Two hundred seventy-seven consecutive patients were included in the analyses. Of these, 73 were treated with 3GC, 39 with piperacillin/tazobactam, 104 with quinolones, and 61 with carbapenems. All-cause 30-day mortality was 16% (45 patients). The type of antibiotics was not significantly associated with mortality on univariate or multivariate analyses. With carbapenems as reference, adjusted odds ratios (ORs) for mortality were 0.708, 95% confidence interval (CI) 0.231-2.176 with 3GC; OR 1.172, 95% CI 0.388-3.537 with piperacillin/tazobactam; and OR 0.586, 95% CI 0.229-1.4 with quinolones. The main antibiotic was not associated with repeated growth of Entrobacter spp. in blood cultures or other clinical specimens. Resistance development was observed with 3GC and piperacillin/tazobactam. Conclusions: Carbapenem treatment was not advantageous to alternative antibiotics, including 3GC, among patients with Enterobacter spp. bacteremia in an observational study.