Effect of cultivars and irrigation waters on persistence of indicator bacteria on lettuce grown in high tunnel

Yin, Hsin‐Bai; Chen, Chi‐Hung; Karanth, Shraddha; Byun, Suyeun; Mayer, Christine M.; Harriger, Dana; Pradhan, Abani K.; Patel, Jitendra

doi:10.1111/jfs.12795

Cited by 4 publications

(1 citation statement)

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“…Our previous reports investigated the impact of RW and TW irrigation on the microbiological quality of spinach and lettuce by monitoring the transfer of indicator bacteria including total coliforms, fecal coliforms, and generic E. coli from the irrigation water to the produce under different growing conditions (Yin et al, , 2019(Yin et al, , 2020, and the results of these studies support the use of alternative waters for fresh produce irrigation in the Mid-Atlantic area provided that these waters contained acceptable levels of bacterial indicator populations. In the current study, the potential usage of RW and TW as irrigation water sources for fresh produce was further investigated by inoculating known concentrations of E. coli surrogates to the irrigation water and then determining the transfer and persistence of these surrogates on the irrigated lettuce.…”

Section: Discussionmentioning

confidence: 90%

Persistence of Escherichia coli O157:H12 and Escherichia coli K12 as Non-pathogenic Surrogates for O157:H7 on Lettuce Cultivars Irrigated With Secondary-Treated Wastewater and Roof-Collected Rain Water in the Field

Yin

Gupta

Chen

et al. 2020

Front. Sustain. Food Syst.

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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-toxigenic Escherichia 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-pathogenic E. coli strains as surrogates for E. coli O157: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−1 of a mixture of nalidixic acid-resistant E. coli O157:H12 and chloramphenicol-resistant E. coli K12 in fecal slurry as non-pathogenic surrogates for E. coli O157: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 of E. coli O157:H12 was significantly greater than the populations of E. coli K12 recovered from the irrigated lettuce regardless of the water sources and the lettuce cultivars. The TW irrigation resulted in the lowest recovery of the E. coli surrogates 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 of E. coli O157: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 specific E. coli surrogates 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. coli O157:H12 could be a more suitable surrogate compared to E. coli K12 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.

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Section: Discussionmentioning

confidence: 90%