Isolation and characterization of bacterial pathogens in fresh cut vegetables and the effectiveness of routinely used disinfectants
Abdulrehman, Fatma A.
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Vegetables are known to contribute immensely to humans both in terms of nutritive value and economically. Shoking findings now indicate that vegetables are heavily contaminated by various pathogenic bacteria. Hundreds of millions of people around the world have fallen sick after consuming contaminated vegetables, which contribute to increased health care costs, reduced workforce productivity and diminished quality of life. The risks associated with microbiological hazards of raw vegetables are not well documented in Kenya making this an important area for investigation. This study characterized common bacterial pathogens in fresh cut sanitized and un-sanitized vegetables from Nyeri, Nanyuki and Nairobi, assessed the effectiveness of commonly used disinfectants, determined antibiotic sensitivity profiles of the isolated bacterial pathogens and assessed the genetic relationships among these pathogenic bacteria. Five hundred are ten samples of which 53.2% were from Nyeri, 39.2% and 7.6% from Nairobi and Nanyuki respectively, from 30 different vegetable types were collected. Three hundred and ninety three different bacteria were isolated. This included 25.4% Faecal E. coli, 4.6% Listeria monocytogenes, 1.5% Staphylococcus aureus, 1.3% Shigella flexneri, 1.8% Aeromonas hydrophila, 1% Salmonella while Hafnia alvei, K. onithinolytica K. ozonae, X. maltophila, E. sakazakii, Rahnella aequatilis, Providencia rettgeri and Erwinia species were isolated only rarely, this prevalence significantly varied with vegetable type and location of isolation (P = 0.039). Pathogenic bacteria such as Bacillus cereus, Vibrio cholera and Yersinia enterocolitica were not detected. All the bacterial isolates were sensitive to ciprofloxacin and gentamicin (P = 0.018) however majority of bacterial isolate were resistant to ampicilin, chloramphenicol, sulphamethaxazole/ trimethroprim, cefotaxime and tetracycline ( P > 0.719). Sanitized vegetables with chlorine and QAC significantly reduced contamination (P = 0.0001). Out of 43 and 26 bacterial isolates analyzed using RAPD and ERIC 12 and 9 different loci that were all polymorphic were obtained. Moderate genetic diversity between RAPD and ERIC 0.3707 and 0.4721 respectively were observed however no genetic exchange between the bacterial isolates was observed Nm = 0 and two divisions at a large dissimilarity distance 0.43 and at 0.45 were obtained between isolates analysed using RAPD and ERIC respectively. This study showed that vegetables are easily contaminated with various pathogenic bacteria however sanitization significantly reduced the extent of contamination. Ciprofloxacin and gentamicin are the drugs of choice. Higher genetic diversity was obtained with ERIC than RAPD which also significantly differentiated different bacterial isolates into different clusters. The information of the data generated from this study will be useful in developing guidelines for reducing the risk of diseases caused by consumption of contaminated vegetables.