MOLECULAR CHARACTERISATION AND DISTRIBUTION OF ANTIBIOTIC-RESISTANCE GENES AMONG MULTIDRUG-RESISTANT ESCHERICHIA COLI FROM CLINICAL SAMPLES IN NIGERIA

Background: Antimicrobial resistance in Escherichia coli is an important clinical and public-health problem in Nigeria.Published reports describe extended-spectrum β-lactamases (ESBLs), carbapenemases, plasmid-mediated quinolone resistance, aminoglycoside-modifying enzymes, tetracycline determinants and folate-pathway resistance genes, but the evidence is geographically uneven and methodologically heterogeneous.Objective: To critically synthesise the molecular characteristics, clinical distribution and surveillance implications of antibiotic-resistance genes reported in multidrug-resistant E. coli from human clinical specimens in Nigeria.Methods: A structured narrative review with transparent evidence mapping was undertaken.Searches and citation checks were updated to 27 July 2026 using multidisciplinary scholarly indexes, biomedical publication records, PubMed-indexed pages, reference chaining and authoritative WHO sources.Eligible evidence concerned human clinical E. coli obtained in Nigeria and reported phenotypic antimicrobial susceptibility, PCR-based resistance determinants, whole-genome sequencing (WGS), or a combination.Animal, food and environmental studies were used only for contextual One Health interpretation.Because sampling frames, specimen mixes, isolate-selection rules, susceptibility standards and gene panels differed substantially, results were synthesised narratively and no national pooled prevalence was calculated.Results: Across the evidence base, blaCTX-M-especially blaCTX-M-15-was the most consistently reported ESBL family, frequently co-occurring with blaTEM, blaSHV and non-β-lactam determinants.Clinical genomic studies identified globally disseminated and locally important lineages including ST131, ST410, ST648 and diverse bloodstream-associated clones.blaNDM variants and OXA-48-like enzymes, including OXA-181, were reported in selected clinical settings, but their frequencies cannot be generalised nationally.WGS studies demonstrated extensive lineage diversity, mobile genetic elements and occasional closely related isolate clusters.Major limitations were single-centre designs, selection of resistant subsets, inconsistent denominators, narrow PCR panels, limited allele confirmation and sparse linkage to clinical outcomes.Conclusion: Nigeria has clear evidence of diverse, mobile and clinically consequential resistance determinants in E. coli, but not a representative national molecular prevalence estimate.Master's-level inference requires study-specific denominators, phenotype-genotype reconciliation and explicit separation of infection, colonisation and One Health contextual evidence.Priorities are harmonised sentinel surveillance, diagnostic stewardship, quality-assured AST, representative genomic sampling, shared minimum metadata and sustainable bioinformatics capacity.