SCIENCE

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Browsing SCIENCE by Author "ABAKPA, Grace Onyukwo"

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    HAZARDS ASSOCIATED WITH ENTERIC AGENTS ON VEGETABLES GROWN IN IRRIGATED FIELDS TREATED WITH MANURE IN PARTS OF KANO AND PLATEAU STATES, NIGER
    (2014-03) ABAKPA, Grace Onyukwo
    With increased consumption of vegetables and the number of documented outbreaks of human infections associated with it, this study was instituted. The study assessed the hazards of the presence of enteric agents on vegetables grown in irrigated fields treated with manure in parts of Kano and Plateau States, Nigeria. Semi structured questionnaires were administered to farmers in the study area to ascertain their farm management practices. Four hundred and forty (440) samples comprising vegetables and some environmental samples (water, soil and manure) were obtained from vegetable producing regions in Kano and Plateau States, Nigeria, between May, 2010 and March, 2011. All samples were examined using standard procedures to determine physicochemical characteristics, enumeration of faecal coliform and detection of E.coli O157: H7, Salmonella spp and Vibrio cholerae during the dry and wet seasons. Isolated pathogens were characterized conventionally and molecularly, assayed for toxin production, virulence determinants, and mobile genetic elements by Polymerase Chain Reaction (PCR). Representative isolates were further analysed for genetic relatedness and determination of diversity by Deoxyribonucleic Acid (DNA) Fingerprinting. Farm management practices which include use of untreated wastewater and untreated manure were observed to have contributed greatly to preharvest contamination of vegetables in the study areas. Significant difference (P <0.05) was observed in the level of counts of faecal coliform on vegetables, with vegetables irrigated with untreated water having higher counts than those irrigated with treated water. Vegetables obtained from sites which received contamination from livestock waste had higher (7.79 ± 7.53) faecal coliform counts than other point sources of contamination to irrigation water in Kano State while in Plateau State, higher (7.74 ± 7.67) counts were obtained from vegetables that received contamination from domestic waste. Generally, significantly higher counts (P<0.05) were obtained from vegetables in the wet season than in the dry season. Physicochemical parameters of irrigation water exceeded acceptable limits for irrigation of vegetables for human consumption. Faecal coliform counts (FCC) exceeded World Health Organisation guidelines acceptable limits (1000fcc/100ml) for vegetables and irrigation water. Counts were significantly (P< 0.05) higher in the wet season than in the dry season in Kano State, while in Plateau there was no observed significant difference in counts of coliform between the two seasons. Salmonella spp had the highest prevalence rate of 13.2% in the study with its highest detection rate in vegetables. E. coli O157:H7 had a prevalence of 7.3%, while Vibrio cholerae had 5.7% prevalence in the study. Seasonal distribution of pathogens by odds ratio showed that E.coli O157:H7 was more likely to be detected in the wet season while Salmonella spp and Vibrio cholerae were more likely to be detected in the dry season. Isolates were assayed for toxin production and their virulence potential was ascertained. Escherichia coli O157:H7 produced verocytotoxins (VT), 57.9% of isolates tested produced both VT1 and VT2 while, 61.5% Vibrio cholerae isolates produced cholera toxin (ctx). Antibiogram of isolates obtained showed multiple antibiotic resistance profiles of pathogens to eight commonly used antibiotics in Nigeria. Polymerase Chain Reaction (PCR) amplified some housekeeping genes (uidA), virulence gene markers (rfbo157, invA, stn and ctxA), antibiotic resistance genes and some mobile genetic elements in the pathogens. Enterorepititive Intergenic Concensus DNA Fingerprinting successfully genotyped isolates in the study. Fingerprints revealed genetic similarity among some isolates from vegetables and environmental sources and showed diversity among some. Cluster analysis of Escherichia coli O157:H7 fingerprints at a coefficient of similarity of 0.53 grouped strains into 6 different groups; five clusters and one singleton. Salmonella strains were grouped into five groups; two clusters and three singletons while, Vibrio cholerae strains were grouped into six groups at a coefficient of similarity of 0.62. Sequence analysis of pathogens obtained in the study gave an insight on the prevailing strains of each bacterial type studied in the study locations and probably in Nigeria as a whole. These sequences have been deposited into the Genebank and assigned accession number (Salmonella invA gene KF026356) for reference. We recommend continuous monitoring of these vehicles of pathogen transmission from the environment to the foodchain. The need for proper washing and cooking of vegetables before consumption cannot be overemphasized.