The emergence of bla _NDM / mcr-1 -positive Escherichia coli poses a huge challenge to infection control. The purpose of this study was to investigate the plasmid and genomic characteristics of bla _NDM / mcr-1 -positive E. coli isolates from the gut of healthy individuals. This study performed drug susceptibility testing, whole-genome sequencing (WGS), analysis of resistance genes, characterization of plasmids, and single-nucleotide polymorphism (SNP) analysis on bla _NDM / mcr-1 -positive E. coli isolates collected from the gut of 628 healthy individuals. Our results showed that all seven isolates were extensively drug-resistant, with susceptibility only to tigecycline and streptomycin. Notably, WGS revealed that bla _NDM and mcr-1 were located on transferable plasmids, and SNP analysis placed the isolates in five distinct clades. These findings underscore the need for surveillance to monitor dissemination among healthy populations. IMPORTANCE: This study reports isolation of Escherichia coli strains coharboring the critical resistance genes bla _NDM (carbapenemase) and mcr-1 (colistin resistance) from the guts of healthy individuals (rural China). All seven isolates were extensively drug resistant, susceptible only to tigecycline and streptomycin. Crucially, both resistance genes were located on transferable plasmids, demonstrating potential for horizontal spread. Genomic analysis revealed diverse strains and plasmid types carrying these genes within mobile genetic contexts. This discovery identifies healthy human carriers as a significant reservoir for pan-resistant bacteria, posing severe public health challenges and necessitating urgent surveillance in endemic areas.

This study aimed to investigate the prevalence, genomic features, and plasmid characteristics of carbapenem-resistant Escherichia coli (CR-EC) harboring bla_NDM within a "One Health" framework in rural communities of western Shandong Province, China, to assess potential public health risks. A cross-sectional sampling of human, animal, and environmental sources was conducted. Recovered CR-EC isolates underwent antimicrobial susceptibility testing, whole-genome sequencing, and phylogenetic analysis. Plasmid genetic structure was characterized, and conjugation assays were performed to evaluate the transferability of bla_NDM-carrying plasmids. Among 26 CR-EC isolates, bla_NDM-5 was predominant (84.6%). All strains were extensively drug-resistant. Notably, 10 of 11 isolates belonging to the high-risk global clone ST167 originated from asymptomatic human carriers, suggesting community transmission. Genomic analysis identified IncF-type plasmids carrying bla_NDM with >99% identity to plasmids from clinical strains in Australia and Germany. Conjugation confirmed plasmid transferability. Phylogenetic clustering among human isolates indicated clonal spread, with potential zoonotic links. Multiple virulence genes (e.g., astA, iuc, fim) were detected. The presence of bla_NDM in wastewater highlighted environmental dissemination. The findings reveal the concerning emergence and dissemination of high-risk CR-EC clones in a rural setting, facilitated by mobile genetic elements across human, animal, and environmental reservoirs. This underscores an urgent need for integrated genomic surveillance and targeted interventions to mitigate the spread of CR-EC in community ecosystems.

Escherichia coli sequence type 1193 (ST1193) is an emerging global high-risk clone, but its mother–infant gut carriage remains poorly characterized. Using selective culture, antimicrobial susceptibility testing, and whole-genome sequencing, we analyzed 244 samples collected twice, 6 months apart, from 61 mother–infant dyads in Jinan, China, in 2025. Ciprofloxacin-resistant Enterobacterales were recovered from 55 samples (35/122 maternal [28.69%]; 20/122 infant [16.39%]), yielding 58 isolates because three samples contained two species; 54 were E. coli, and 57 were multidrug resistant. ST1193 was most frequent (17/54, 31.48%); all harbored GyrA S83L/D87N and ParC S80I substitutions, whereas none carried screened plasmid-mediated quinolone resistance (PMQR) determinants. Core-genome multilocus sequence typing identified 11 related clusters among 25 E. coli, involving four of eight positive dyads and seven of 13 longitudinally positive individuals, suggesting sharing or repeated detection without proving transmission or continuous carriage. PMQR genes occurred in 15 non-ST1193 isolates. Five closed circular PMQR-positive plasmids had diverse replicons and resistance cargoes; all contained IS26. Four donors yielded target-gene-positive J53 recipient-background colonies at apparent endpoint frequencies of 4.46 × 10⁻⁷–3.69 × 10⁻⁶. These findings distinguish QRDR-mediated resistance in ST1193 from PMQR-positive non-ST1193 backgrounds; selected PMQR elements showed in vitro transfer potential in this selectively cultured mother–infant cohort.