Characterization of some virulence genes in non-typhoidal Salmonella isolated from food animals and handlers in Lagos

BACKGROUND: Non-typhoidal Salmonella (NTS) serovars are the major cause of Salmonella gastroenteritis which is usually self-limiting; however, this could result in invasive systemic infection in infants, the elderly and immune-compromised people most especially in sub-Saharan Africa. The food chain plays a significant role in Salmonella infections thus several foods could serve as a vehicle of transmission. METHODS: Fifty previously well characterized non-typhoidal Salmonella (NTS) isolates isolated from humans and food animals were used in this study. Five virulence genes (invA, sipB, sitC, sifA and msgA), 4 efflux pumps (acrF, tetC, tetD and mdfA) and one biofilm encoding gene (spiC) were assayed for by polymerase chain reaction (PCR). RESULTS : All 50 (100%) Salmonella isolates harbored invA gene, while 49 (98%) of them possessed msgA gene, sipB sitC and sifA genes were detected in seven (14%), eight (16%) and 27 (54%) of the isolates, respectively. Forty-nine (98%) of the Salmonella isolates were positive for tetC gene. None of the isolates harbored tetD, mdfA and acrF efflux pump genes. SpiC, a biofilm encoding gene was detected in 21 (42%) of the isolates. CONCLUSIONS: Results of this study highlights important virulence factors of Salmonella enterica serovars circulating in the food chain. Continuous surveillance is recommended in order to have updated information on strains and pathogenicity that will help mitigate Salmonella infection outbreak.