Microbes in Irrigation Water and Fresh Vegetables

Irrigated fresh vegetables are a potential portal for dissemination of human pathogens that may be associated with irrigation water source. This study investigated the quality of irrigation water and the fresh vegetables produced in regard to pathogenic bacteria found at a selected vegetable farm in southwestern Nigeria. Enumeration and characterization of total heterotrophic bacteria and potential pathogens (mostly enteric bacteria) were done with international procedures. Susceptibility of the potential pathogens to antibiotics was by disk diffusion techniques, while plasmid profile was by polymerase chain reaction–based DNA fingerprinting. The mean values for total heterotrophic bacteria in irrigation water and fresh vegetable samples were, however, statistically comparable (P = .86). The corresponding comparison for coliform also showed no significant difference (P = .07). The isolated pathogenic bacteria genera from the irrigation water and fresh vegetable samples include Citrobacter, Enterobacter, Escherichia, Klebsiella, Pseudomonas, and Salmonella. In sum, 67.2% of the isolates were obtained from irrigation water samples, compared with 32.8% in the vegetable samples; 54.1% of the isolates were resistant to >1 antibiotic with a multiple antibiotic resistance index >0.2, suggesting an antibiotic pressurized environment. Resistance to ampicillin was very high (98.36%), whereas resistance to ciprofloxacin was very low (0.0%); 27.9% of the multiresistant enteric isolates harbored ≥1 plasmids. There is a possibility of increased numbers of pathogens on irrigated vegetables as a direct consequence of poor irrigation water quality in the study site. The use of pathogen-free irrigation water and good agricultural practices has the potential to eliminate microbial hazards in fresh vegetables.