MOLECULAR CHARACTERIZATION AND TETRACYCLINE RESISTANCE DETERMINANTS OF STOOL-DERIVED SALMONELLA ENTERICA FROM SELECTED TERTIARY HOSPITALS IN KANO, NIGERIA

Abstract

Enteric bacterial infections, especially those caused by Salmonella species, remain a significant public health concern in sub-Saharan Africa, particularly amid rising antimicrobial resistance. This study investigated enteric bacteria specifically Salmonella enterica isolated from 300 stool samples collected from three tertiary hospitals in Kano, Nigeria (AKTH, MAWTH and MMSH), with emphasis on molecular characterisation and tetracycline resistance in Salmonella enterica. Escherichia coli was the predominant isolate, 27.7% (83/300), followed by Proteus mirabilis 5.7 % (17/300), Citrobacter species 5.3% (16/300), Enterobacter species 4.0% (12/300), Yersinia species 1.7% (5/300), and Salmonella enterica 1.3% (4/300), reflecting pathogen distributions commonly reported across African settings. Four Salmonella isolates (1.3%) were confirmed as Salmonella enterica by 16S rRNA gene sequencing, with sequence similarity ranging from 96.05–97.64% to reference strains. Phylogenetic analysis demonstrated clustering with internationally reported serovars from South Africa, China, and India, indicating global lineage relatedness. The sequences were deposited in GenBank (PP857911.1–PP857914.1), contributing to global surveillance datasets. PCR screening of tetracycline-resistant isolates revealed universal detection of the tetD gene (4/4) and tetB in one isolate, while tetA, tetC, tetO, and tetS were not detected. The predominance of tetD contrasts with many global reports in which tetA and tetB are more common, suggesting a distinct local resistance profile, potentially driven by regional antibiotic selection pressures and mobile genetic elements. The presence of efflux-mediated resistance determinants highlights the risk of horizontal gene transfer and the possible emergence of multidrug-resistant strains. These findings underscore the need for strengthened antimicrobial stewardship, expanded molecular surveillance, and broader profiling of resistance genes to mitigate the spread of resistant Salmonella enterica in northern Nigeria.