Temocillin efficacy against AmpC β-lactamase-producing Enterobacterales: a relevant alternative to cefepime?

Introduction: Temocillin is a semi-synthetic β-lactam with a narrow spectrum but high stability against hydrolysis by β-lactamases, including AmpC. Despite its favourable properties, data regarding its clinical value in the treatment of AmpC β-lactamase-producing Enterobacterales (ABPE) infections are scarce. Most recent guidelines do not include temocillin in the therapeutic strategy for ABPE infection.

Objectives: This study investigated (i) the proportion of ABPE isolates susceptible to temocillin and (ii) the clinical outcomes of patients treated with temocillin for ABPE infections.

Materials and methods: This retrospective multicentre (Bordeaux and Reunion Island) study was performed in two parts. First, all the antimicrobial susceptibility test (AST) results of ABPE isolated from May 2021 to August 2023 were included in the analysis. Second, all patients who had received at least one dose of temocillin for ABPE infection between 2017 and 2023 were analysed. The electronic clinical records of these patients were reviewed to determine their treatment outcomes. Therapeutic success was defined as the absence of relapse one month after the end of temocillin treatment (3 months in the case of bone and joint infection) and the absence of treatment modification following an unfavourable outcome.

Results: During the microbiologic period of investigation (2021-23), 5166 ABPE strains were included. Of these, 4253 (82%) were susceptible to temocillin, whereas 4564 (88%) were susceptible to cefepime. After restriction to third-generation cephalosporin-resistant (3GCR) ABPE strains (n = 1446), the proportion of strains susceptible to temocillin was 66% (n = 1227) versus 59% (n = 1092) for cefepime. Temocillin treatment was initiated in 67 patients with ABPE infection during the study period (2017-23). The main infections were complicated urinary tract infections (n = 32, 48%) and bone and joint infections (n = 15, 22%). The estimated overall success rate for patients who underwent complete follow-up was 89% (n = 56/63).

Conclusions: Temocillin appears to be reliable for ABPE infections. Our data showed a high therapeutic success rate. Its high tolerability, narrow spectrum and ease of administration could make temocillin a relevant alternative to cefepime, the current standard for ABPE infection.