Prevalence of extended-spectrum β-lactamase-producing Enterobacterales and carbapenemase-resistant Enterobacterales in British military cohorts.

Introduction: Travel to resource-limited settings is a known risk for acquisition of extended-spectrum β-lactamase-producing Enterobacterales (ESBL-PE) and carbapenem-resistant Enterobacterales (CRE), which are both associated with increased morbidity and mortality. We investigated the ESBL-PE and CRE baseline prevalence in British service personnel (SP).

Methods: SP provided faecal samples for research projects in several different settings, between September 2021 and April 2022. Bacterial colonies from faecal isolates were recovered from incubated ChromID ESBL plates (bioMérieux, Marcy-l'Étoile, France) and DNA extracted using Qiagen DNeasy extraction kits (Qiagen, UK). PCR to identify β-lactamase and CRE encoding genes was performed using the Rotor-Gene Q (RGQ) (Qiagen, UK), with positivity detected by RGQ software. Phenotypic assessment of antimicrobial susceptibility was not performed.

Results: Out of 250 personnel approached, 239 (85.5% men, median (IQR) age 31 (26-37) years) provided faecal samples suitable for analysis. The ESBL prevalence was 40/239 (16.7%), with ESBL-producing Escherichia coli detected in 39 (16.3%) samples and ESBL-producing Klebsiella pneumoniae in 1 (0.4%) sample. Combinations including Temoniera, sulfhydryl reagent variable (SHV), cefotaxime hydrolysing β-lactamase (Munich) (CTX-M) 1 and CTX-M 9 genes were detected in 18 (7.5%), 33 (13.8%) 16 (6.7%) and 8 (3.3%) samples, respectively. E. coli samples had mixtures of all four genotypes with SHV predominating. One (0.4%) sample carried all four gene types and the only K. pneumoniae sample carried a single SHV gene. No CRE were detected.

Conclusions: The prevalence of ESBL-PE in cohorts of SP closely matches that of civilian populations in England; however, we noted differences in ESBL genotype distribution. Potential exposure risks for SP from international travel and occupational trauma emphasise the need for repeated surveillance to characterise and detect changes in acquisition epidemiology and carriage of ESBL. Such prospective data have important antimicrobial stewardship implications in optimising clinical outcomes, controlling resistance and guiding empirical antibiotic formulary policy recommendations.