Molecular Detection of Virulence Genes in Escherichia coli and Salmonella enterica Isolated from Minimally Processed Foods Sold within Kaduna Metropolis

Abstract

This study was aimed at detecting virulence genes in enteropathogenic bacteria associated with minimally processed foods sold within Kaduna metropolis. Samples of sliced watermelons, peeled sugarcanes, peeled and sliced pineapples and unshelled coconuts (n=140) were collected from Kaduna North, Kaduna South and Igabi LGAs. Upon enrichment, samples were inoculated onto Eosin-Methylene Blue (EMB) and Cefixime-Tellurite-Sorbitol MacConkey (CT-SMAC) agar and incubated for 18 hours at 35oC. Isolates were identified using MicrobactTM 24E Gram Negative Bacteria Identification System for Enterobacteriaceae. Thereafter, E. coli and Salmonella enterica isolates’ DNA was extracted and purified using AccuPrep Genomic DNA Extraction Kit; used as a template for the PCR amplification of the bundle forming pilus (bfpA) and invasion (invA) genes; and then the PCR products were visualised using agarose gel electrophoresis documentation system. The results of the MicrobactTM analyses showed widespread contamination of the samples with E. coli (22 isolates) and Salmonella enterica (3 isolates). There was no statistically significant difference in the bacterial contaminants isolated from the various sampling areas (one-way ANOVA: p = 0.577); similarly, the type of the minimally processed food samples had no influence on the prevalence of E. coli and Salmonella enterica isolates (p = 0.345). PCR result revealed that the invA virulence gene (284bp) was present in one Salmonella enterica isolate. The presence of invA gene in the Salmonella enterica isolate indicated that the isolate is a virulent strain, which can cause food-borne infections. These results indicated the contamination of the minimally processed fruits with enteropathogens, hence, standards of quality control should be enshrined, towards safer foods and enhanced health of the consuming populace. Keywords: E. coli; virulence gene; minimally processed foods; Salmonella enterica.