Abstract
Treated wastewater (TW) and roof-collected rain water (RW) that meet the required microbial quality as per Food Safety Modernization Act (FSMA) regulation may serve as alternative irrigation water sources to decrease the pressure on the current water scarcity. Alternative water sources may have different water characteristics that influence the survival and transfer of microorganisms to the irrigated produce. Further, these water sources may contain pathogenic bacteria such as Shiga-toxigenicEscherichia coli. To evaluate the risk associated with TW and RW irrigation on the fresh produce safety, the effect of TW and RW irrigation on the transfer of two non-pathogenicE. colistrains as surrogates forE. coliO157:H7 to different lettuce cultivars grown in the field was investigated. Lettuce cultivars “Annapolis,” “Celinet,” and “Coastline” were grown in the field at the Fulton farm (Chambersburg, PA). Approximately 10 days before harvest, lettuce plants were spray-irrigated with groundwater (GW), TW, or RW containing 6 log CFU ml−1of a mixture of nalidixic acid-resistantE. coliO157:H12 and chloramphenicol-resistantE. coliK12 in fecal slurry as non-pathogenic surrogates forE. coliO157:H7. On 0, 1, 3, 7, and 10 days post-irrigation, four replicate lettuce leaf samples (30 g per sample) from each group were collected and pummeled in 120 ml of buffered peptone water for 2 min, followed by spiral plating on MacConkey agars with antibiotics. Results showed that the recovery ofE. coliO157:H12 was significantly greater than the populations ofE. coliK12 recovered from the irrigated lettuce regardless of the water sources and the lettuce cultivars. The TW irrigation resulted in the lowest recovery of theE. colisurrogates on the lettuce compared to the populations of these bacteria recovered from the lettuce with RW and GW irrigation on day 0. The difference in leaf characteristics of lettuce cultivars significantly influenced the recovery of these surrogates on lettuce leaves. Populations ofE. coliO157:H12 recovered from the RW-irrigated “Annapolis” lettuce were significantly lower than the recovery of this bacterium from the “Celinet” and “Coastline” lettuce (P< 0.05). Overall, the recovery of specificE. colisurrogates from the RW and TW irrigated lettuce was comparable to the lettuce with the GW irrigation, where GW served as a baseline water source.E. coliO157:H12 could be a more suitable surrogate compared toE. coliK12 because it is an environmental watershed isolate. The findings of this study provide critical information in risk assessment evaluation of RW and TW irrigation on lettuce in Mid-Atlantic area.
Highlights
The World Health Organization encourages people to consume at least 400 g of fresh produce such as fruits and vegetables per day to prevent chronic disease including heart disease, diabetes, and obesity (World Health Organization, 2018)
The current study investigated the applicability of rain water (RW) and treated wastewater (TW) as alternative agricultural water sources for fresh produce irrigation
The transfer of two non-pathogenic E. coli surrogates from GW, RW, and TW to “Annapolis,” “Celinet,” and “Coastline” cultivars of lettuce grown in the field was examined
Summary
The World Health Organization encourages people to consume at least 400 g of fresh produce such as fruits and vegetables per day to prevent chronic disease including heart disease, diabetes, and obesity (World Health Organization, 2018). Attachment of human bacterial pathogens on fresh produce during spray irrigation can be affected by the bacterial strains, bacterial population, stress tolerance, and their biofilm formation ability (Carey et al, 2009; Ge et al, 2012; Yaron and Römling, 2014; Kljujev et al, 2018). Other factors such as produce growing conditions, plant development stage, and the leaf characteristics of cultivars affect bacterial attachment on the fresh produce leaf (Barak et al, 2011; Ge et al, 2012; Hirneisen et al, 2012; Quilliam et al, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
