Global Diffusion of IncC Plasmid Harboring blaNDM-1in the High-Risk Escherichia coli ST131 Clone

The global expansion of quinolone-resistant Escherichia coli (QR-EC) is increasingly associated with β-lactam resistance and mobile genetic elements that facilitate resistance dissemination. This study investigated the molecular mechanisms underlying fluoroquinolone and β-lactam resistance in clinical QR-EC isolates and explored the plasmid type associated.

A total of 123 non-duplicate QR-EC clinical isolates responsible mainly for gastrointestinal colonization were collected between 2019 and 2021. Plasmid-mediated quinolone resistance (PMQR), extended-spectrum β-lactamase (ESBL), and carbapenemase genes were screened by PCR. Mutations in the quinolone resistance-determining regions (QRDR) of gyrA and parC were analyzed using sequencing and mismatch amplification mutation assay PCR (MAMA-PCR). Selected isolates underwent multilocus sequence typing (MLST). Whole-genome sequencing (WGS) of a representative extensively drug-resistant strain carrying multiple quinolone resistance determinants, ESBL genes, and carbapenemase genes, was performed. PMQR genes were prevalent among QR-EC, dominated by aac(6')-Ib-cr (60.9% of isolates). ESBL genes were identified in 93.5% of isolates, predominantly blaCTX-M (95.7%). Among ertapenem-resistant isolates (QCR-EC) (n=18), blaNDM-1 and blaOXA-48 were detected in 13 and 11 isolates, respectively. QRDR mutations were highly frequent, particularly gyrA83 (98.4%) and parC80 (30.9%). Major QCR-EC genotypes belonged to sequence types ST167 (n=2), ST1196, ST469, and ST410. High-risk E. coli ST131 clone harboring IncC plasmid encoding blaNDM-1 was described for the first time in Africa, following its emergence, in two continents, Asia and America. Despite the very rare description of these strains worldwide, their description in three continents sign their global diffusion.

This finding highlights the ongoing spread of carbapenem resistance and underscores the urgent need for strengthened genomic surveillance.