Molecular detection of salmonella species from selected vegetables sold in a north-central Nigerian setting

Abstract

It is vital to study and understand the genetic basis to the virulence of different Salmonella strains in other to fully grasp the facts behind the unique capabilities of these pathogenic agents to causing diseases in both humans and animals. In this study, the conventional microbiological culture methods were used to isolate pure Salmonella strains from 120 vegetable samples of five different types; which were all obtained at seven different popular markets in the Jos Metropolis of North Central Nigeria. 25 (20.8%) pure isolates were obtained from 120 samples after initial culture and sub-cultures; with 24 (20%) of the pure isolates testing positive as being pathogenic after biochemical analysis. From the 25 pure isolates, the same 24 which tested positive for biochemical tests were also successfully amplified by PCR technique with the Salmonella invA virulence gene. The result shows that 96% of the pure isolates were positive for the Salmonella invA gene. The PCR product which was very specific is a 250bp fragment of DNA which was visualized in 1.5% agarose gel. This finding shows that virulent Salmonella strains pose a major health hazard and public health concern to the affected population. Our study shows that there is a high prevalence rate of virulent Salmonella strains in North-Central Nigeria. It is thus concluded that although both the conventional culture and biochemical methods of isolating Salmonella species are most useful for obtaining pure isolates and identifying pathogenic strains, however, the PCR technique remains the most specific and sensitive; especially when the rapid identification and detection of virulent strains of Salmonella species are of utmost importance.

Keywords: Virulence, invA gene, PCR, North Central Nigeria