Abstract
<jats:p>Enteric fever remains a significant public health burden in sub-Saharan Africa, yet the phylogenetic diversity of circulating Salmonella serovars in Nigeria remains incompletely characterized. While typhoidal strains dominate clinical reports, emerging atypical lineages and non-typhoidal serovars may contribute substantially to febrile illness transmission. A health facility-based cross-sectional study enrolled 425 consecutive febrile patients (aged 1–65 years) with suspected enteric fever in Keffi Local Government Area, Nasarawa State, Nigeria. Blood cultures were processed using the BD Bactec™ automated system, followed by sub-culturing on selective media and presumptive phenotypic screening. Molecular confirmation employed PCR amplification of the 16S rRNA gene (27F/1492R) and Sanger sequencing. Sequence analysis utilized BLASTn against the NCBI GenBank database, and phylogenetic trees were constructed in MEGA 11 using the Maximum Likelihood method with 1,000 bootstrap replicates. Sixty-three (14.8%) blood cultures yielded microbial growth, of which 32 (7.5%) were phenotypically identified as Salmonella. Molecular characterization confirmed 25 isolates (5.9%) as Salmonella species. Phylogenetic analysis resolved four major clades dominated by closely related non-typhoidal Salmonella enterica serovars, particularly S. Typhimurium (n=11), with moderate to strong bootstrap support (68–89%). Emerging atypical lineages, including Salmonella bongori (n=1) and Salmonella enterica subsp. diarizonae (n=1), formed distinct divergent branches separate from the core S. enterica lineages. Additional serovars identified included S. Enteritidis (n=1), S. Typhi (n=1), S. Paratyphi B (n=1), S. Heidelberg (n=1), S. Infantis (n=1), S. Livingstone (n=1), and untyped S. enterica strains (n=6). Substantial phylogenetic diversity exists among Salmonella serovars circulating in suspected enteric fever cases in Keffi, with S. Typhimurium representing the predominant lineage and emerging atypical serovars (S. bongori and S. diarizonae) suggest potential zoonotic and environmental transmission pathways. These findings underscore the urgent need for routine molecular surveillance, enhanced diagnostic capacity, and One Health-based interventions for effective disease control in Nigeria.</jats:p>