Preserving the antimicrobial arsenal: exploring alternatives to carbapenems in ESBL battles within the southeast of Ireland

<b>Introduction.</b> Carbapenems are usually employed as first-line antimicrobials against bacteria harbouring extended-spectrum beta-lactamases (ESBLs). These enzymes confer resistance often to multiple classes of antimicrobials.<b>Hypothesis/Gap Statement.</b> This indiscriminate use of carbapenems and the inevitable development of carbapenem resistance have prompted the need for carbapenem-sparing strategies.<b>Methodology.</b> The non-carbapenem antimicrobial susceptibility patterns of 60 ESBL-producing <i>Enterobacterales</i> (ESBL-PE) isolates responsible for bloodstream infections, in 2022-2023 inclusive, processed at our institution were reviewed.<b>Results.</b> The non-carbapenem antimicrobial susceptibility patterns of 60 ESBL-PE isolates from bloodstream infections during the study period were determined. <i>Escherichia coli</i> was the most common species isolated (87%, <i>n</i>=52), with the majority of cases (73.3%, <i>n</i>=44) originating from a presumed urinary source. Temocillin (TMC), mecillinam (MEC), cefiderocol (FDC), amikacin and fosfomycin (FOS) displayed excellent activity against all ESBL-PE isolates tested, with susceptibility rates of≥85%. Ciprofloxacin and amoxicillin-clavulanic acid were the least efficacious agents, with susceptibility rates≤20%.<b>Conclusions.</b> TMC, MEC, FDC and FOS offer promising alternatives to carbapenems, demonstrating efficacy against ESBL-PE. The use of these agents not only broadens the therapeutic arsenal against ESBL-PE but also mitigates the potential for escalating carbapenem resistance, especially in regions where the incidence of carbapenem resistance is increasing.