Irrigation water quality and microbial safety of leafy greens in different vegetable production systems: A review

Abstract

Access to large sources of quality water for irrigation is fundamental to the hygienic cultivation of fresh produce. However, due to factors such as contamination of water bodies, access to clean uncontaminated water is fast becoming an ever increasing global challenge. The unavailability of quality source water increases the risk of contamination of fresh produce with human pathogenic microorganisms, which may compromise public health. Over the past few years, there has been a decline in the microbiological quality of surface water and other sources used for irrigation. This is mainly due to upstream faecal contamination. Therefore, the assessment and subsequent suitability of alternative water sources for irrigation such as roof harvested rainwater should be considered. Contrasting views regarding the quality of roof harvested rainwater (RHRW) have been published. Pathogens such as Salmonella and Campylobacter species and Listeria monocytogenes have been reported in RHRW. Leafy green vegetables such as cabbage, spinach and lettuce are produced across a wide range of farming systems from 2 regulated formal (commercial farms) to informal (small-scale and homestead gardens) setups. This review will discuss global water challenges associated with irrigation water, microbial quality of source water for irrigation, crop contamination, and pathogen detection and characterization methodologies.

Microbial Contamination of Fresh Produce: What, Where, and How?

“…Contamination of fresh produce with E. coli strains as a result of splash dispersal from contaminated soil surface or manure‐amended soil, mediated by either rain or irrigation water droplets, has been demonstrated (Cevallos‐Cevallos, Danyluk, Gu, Vallad, & van Bruggen, ; Girardin et al., ; Monaghan & Hutchison, ). Contaminated irrigation water is also a possible vector for crop contamination (Jongman & Korsten, ). Microbial internalization into edible portions of RTE foodstuffs, such as tomato, sprouts, and lettuce, has been reported (Franz & van Bruggen, ; Murphy et al., ) and poses a serious health threat as internalized pathogens will most likely not be removed by sanitation processes, either at postharvest or at the final consumption stage.…”

“…Water can be an important source of microbial contamination. Water used for irrigation of produce, as well as pesticide application, cooling, or protection of crops from frost, can be sourced from municipal water supplies, groundwater, recovered rainwater, surface water, or reutilized wastewater (Jongman & Korsten, ). Water sources of poorer microbiological quality (surface water and reutilized wastewater) can be a source of contamination of fresh crops.…”

Shiga-Toxin Producing Escherichia Coli in Brazil: A Systematic Review

“…Contaminated water is increasingly linked to STEC outbreaks associated with fruits and vegetables in Europe [56]. Although STEC contamination is usually related to products of animal-origin, contamination of plant products occurs as a result of cross-contamination [57]. In Brazil, STEC prevalence rates in water ranged from 0.65 to 5.93% with only a single sample testing positive for O157:H7.…”

Preharvest Transmission Routes of Fresh Produce Associated Bacterial Pathogens with Outbreak Potentials: A Review

“…An alternative source of irrigation water is municipal water. Though it is believed to have a high microbiological standard because of the treatment processes it undergoes, its usage for irrigation purposes is discouraged in many countries because it is expensive and not generally available [15]. Agricultural soil also serves as a natural reservoir of enteric pathogens.…”