Microbiological and chemical quality of leafy green vegetables in Accra, Ghana
Quansah, Joycelyn Kwansima
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The study was undertaken to determine vegetable farming and selling practices in Accra, Ghana; microbial quality of leafy green vegetables grown or sold in the area; antibiotic resistance profiles of Salmonella isolated from the vegetables; and the effectiveness of sanitation methods commonly used by Ghanaian households in inactivating Salmonella. Questionnaires were administered to vegetable farmers (n = 102) and sellers (n =37), and a total of 328 exotic (lettuce and cabbage) and indigenous (Amaranthus, Solanum macrocarpon, Hibiscus sabdariffa, and Corchorus olitorius) leafy green vegetables were subsequently collected. Microbial quality of collected samples was determined. Lettuce and cabbage inoculated with Salmonella were treated with sterile water or sanitizers commonly used by Ghanaian households. The effectiveness of the treatments was compared and consumer preference on treated vegetables evaluated. Survey results revealed that water from waste drains and poultry manure were commonly used in vegetable farming. Vegetables were transported in sacks (87%) and stored under non-refrigerated conditions. Results of microbial analysis revealed mean aerobic bacteria, yeast and mold, fecal coliform, and enterococcus counts on collected vegetables were 8.80, 4.95, 4.90, and 3.67 log CFU/g, respectively. Salmonella was isolated from 10% of the vegetables. The Salmonella isolates (n = 33) were resistant to at least one antibiotic and approximately 30% of the isolates were multidrug resistant. One (3%) Salmonella isolate tested positive for integrase gene and class 1 integron gene cassette (800 kb in size) with a single gene, dfrA7. Results of the sanitation study suggest that treatments of cabbage with chlorine, citric acid, peracetic acid, and vinegar and lettuce with citric acid were significantly (p≤0.05) effective in reducing Salmonella counts compared to the other evaluated sanitizers. A 97-member consumer panel preferred (p≤0.05) cabbage treated with citric acid, vinegar, and water and lettuce treated with citric acid and water. In conclusion, vegetable farmers and sellers in the area need additional trainings on food safety. The sampled leafy green vegetables had poor microbial quality, therefore consumption without sanitizing or heat treatment should be discouraged. Sanitizing vegetables with vinegar or citric acid at homes is an effective approach to prevent vegetable transmitted infectious diarrheal diseases.