Molecular Characterisation of Salmonella Serotypes Causing Enteric Fever in Children Across North West Nigerian States

Enteric fever caused by Salmonella enterica serovars Typhi and Paratyphi continues to impose significant morbidity on Nigerian children, yet serotype diversity, antimicrobial resistance profiles, and molecular epidemiology across the North West zone are inadequately characterised. This study molecularly characterises Salmonella serotypes causing enteric fever in children at tertiary hospitals in Kano, Kebbi, and Sokoto States. Blood and bone marrow culture samples from 180 children with clinical enteric fever were processed by standard culture on blood and CLED agar. Salmonella serotyping was performed by slide agglutination with Kauffmann-White scheme antisera and confirmed by multiplex PCR. Whole genome sequencing was performed on 40 representative isolates. Antimicrobial susceptibility testing covered 14 antibiotics. Salmonella Typhi accounted for 79 percent of isolates, with H58 haplotype dominating the sequenced subset. Multidrug resistance to ampicillin, chloramphenicol, and cotrimoxazole was present in 68 percent. Azithromycin-resistant isolates were identified in 11 percent, signalling an emerging treatment threat. Sequencing identified qnr plasmid-mediated fluoroquinolone resistance in five isolates. The study establishes the first molecular epidemiology dataset for enteric fever Salmonella in the North West zone and informs empirical treatment guidelines and typhoid conjugate vaccine priority. Keywords: Salmonella Typhi, enteric fever, molecular epidemiology, North West Nigeria, antimicrobial resistance