Genetic relatedness of resistant toxigenic Vibrio cholerae from wastewater Irrigated vegetables from two major produce regions.

Abstract

Nigeria suffers episodes of cholera outbreak every year often starting from the northern part of the country. The infection is often linked to contaminated food, water and poor hygiene. Vegetables are often irrigated with untreated wastewater in the country. This study aimed at assessing the presence of Vibrio cholerae, their virulence, resistant gene profiles and further elucidated their genetic relationships using PCR-based fingerprinting method; Enterobacterial repetitive intragenic consensus Polymerase Chain Reaction (ERIC-PCR) from two major produce regions in Nigeria. Four hundred and forty samples including wastewater used for irrigation, irrigated vegetables and manure treated soils were analyzed. Isolates were characterized using conventional and molecular techniques. Strains were serotyped, assayed for their toxigenic potentials and resistance to antimicrobial agents. Twenty-five of the samples (5.7%) were positive for Vibrio cholerae, of which 10.2% were detected from soil/manure samples. All strains were found to possess the ctxA gene and exhibited multiple drug resistance. Genotyping by ERIC-PCR of genomic DNA from 15 representative strains obtained resulted in the amplification of multiple fragments of DNA in sizes ranging from 150bp to 1kb. Cluster analysis at a coefficient of 0.62 grouped the strains into six different groups; five clusters and one singleton in simple-match (Sm) similarity group. Strains from vegetables and environmental samples were found clustered together. To the best of our knowledge it is the first report of microbial source tracking and genotypic relatedness of Vibrio cholerae from irrigated vegetables in the country. The need for continuous monitoring and surveillance of potential risk routes in the environment cannot be over emphasized.