Temporal Surveillance of Multidrug-Resistant Salmonella Typhi in Niger State, Nigeria: A 10-Year Phenotypic and Cross-Sectional Study (2014–2024)

The global threat of antimicrobial-resistant Salmonella enterica serovar Typhi (S. Typhi) is intensifying. Yet, long-term surveillance data from regions where it is endemic remain limited. In Nigeria, the crisis has been worsened by fragmented diagnostics and the unregulated use of antibiotics. This study investigated the temporal evolution of phenotypic resistance in S. Typhi across Niger State, Nigeria, over a ten-year period by integrating retrospective and prospective epidemiological data. We conducted a hybrid observational study (2014–2024) that retrospectively analyzed hospital records and performed prospective microbiological surveillance across nine communities. The isolates were confirmed by biochemical and serological tests. Antimicrobial susceptibility testing followed the CLSI guidelines. Logistic regression identified predictors of multidrug resistance (MDR). Among the 624 participants, 228 (36.5%) tested positive for S. Typhi. MDR was observed in 75.9% of isolates, while 5.7% met the strict MDR criteria. Resistance to amoxicillin-clavulanate, cotrimoxazole, and tetracycline reached 100%, 73.5%, and 79.5%, respectively. Levofloxacin and netilmicin retained >80% efficacy. Young adults and semi-urban residents were disproportionately affected. Hospitalization and recent antibiotic use were significant predictors of MDR (p < 0.05). S. Typhi in Niger State shows escalating resistance with narrowing treatment options. Without urgent interventions, revised empirical protocols, vaccine rollouts, and antimicrobial regulations, Nigeria risks entering a post-antibiotic era of typhoid treatment.