Conjugative Transfer of Antibiotic Resistance Genes among Enterobacteriaceae in Nigeria: A Systematic Review, Meta-analysis and Molecular Validation

Background: Horizontal gene transfer (HGT), particularly through plasmid-mediated conjugation, is the principal mechanism driving the dissemination of antimicrobial resistance (AMR) genes among Enterobacteriaceae. In Nigeria, numerous studies have reported the conjugative transfer of clinically important resistance determinants, including extended-spectrum β-lactamase (ESBL) genes, colistin resistance genes, and aminoglycoside-modifying enzymes. However, the available evidence remains fragmented, with considerable variation in reported transfer frequencies, bacterial species, resistance genes, and laboratory methodologies. No systematic review or meta-analysis has previously synthesised these data quantitatively, and few studies have validated pooled epidemiological findings through independent laboratory experiments. Aim: This study aimed to systematically evaluate the prevalence of horizontal gene transfer of antimicrobial resistance genes among Enterobacteriaceae in Nigeria through random-effects meta-analysis and to experimentally validate the conjugative transfer of the blaCTX-M gene. Methods: A systematic review and meta-analysis were conducted in accordance with the PRISMA 2020 guidelines. Six electronic databases (PubMed/MEDLINE, Scopus, Web of Science, ScienceDirect, African Journals Online, and Google Scholar) were searched from inception to December 2025. Studies reporting quantitative conjugation experiments involving Enterobacteriaceae in Nigeria were included. The primary outcome was the HGT frequency, expressed as the proportion of successful transfer events. Pooled estimates were calculated using a random-effects model (DerSimonian and Laird method) in Comprehensive Meta-Analysis software, Version 4. Heterogeneity was assessed using Cochran's Q, I², and τ² statistics. Predefined subgroup analyses were performed by resistance gene type, gene family, confirmation method, and donor–recipient relationship. Publication bias was evaluated using funnel plot inspection and Begg and Mazumdar's rank correlation test. A leave-one-out sensitivity analysis assessed the robustness of the pooled estimate. For experimental validation, broth mating conjugation assays were performed using Escherichia coli donor isolates harbouring blaCTX-M genes and an azide-resistant E. coli J53 recipient. Putative transconjugants were screened by polymerase chain reaction (PCR) and confirmed by agarose gel electrophoresis.