Genomic characterization of extended-spectrum β-lactamase-producing Enterobacterales isolated from abdominal surgical patients.

Rectal swabs of 104 patients who underwent abdominal surgery were screened for ESBL producers. Sequence types (STs) and resistance genes were identified by whole-genome sequencing of 46 isolates from 17 patients. All but seven isolates were assigned to recognized STs. While 18 ESBL-producing E. coli (EPEC) strains were of unique STs, ESBL-producing K. pneumoniae (EPKP) strains were mainly ST14 or ST15. Eight patients harboured strains of the same ST before and after abdominal surgery. The most prevalent resistant genes in E. coli were bla(EC) (69.57%), bla(CTX-M) (65.22%), and bla(TEM) (36.95%), while bla(SHV) was present in only K. pneumoniae (41.30%). Overall, genes encoding β-lactamases of classes A (bla(CTX-M), bla(TEM), bla(Z)), C (bla(SHV), bla(MIR), and bla(DHA)), and D (bla(OXA)) were identified, the most prevalent variants being bla(CTX-M-15), bla(TEM-1B), bla(SHV-28), and bla(OXA-1.) Interestingly, bla(CMY-2), the most common pAmpC β-lactamase genes reported worldwide, and mobile colistin resistance genes, mcr-10-1, were also identified. The presence of bla(CMY-2) and mcr-10-1 is concerning as they may constitute a potentially high risk of pan-resistant post-surgical infections. It is imperative that healthcare professionals monitor intra-abdominal surgical site infections rigorously to prevent transmission of faecal ESBL carriage in high-risk patients.