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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Publications at this Location » Publication #361112
Research Project: Characterization and Mitigation of Bacterial Pathogens in the Fresh Produce Production and Processing Continuum

Location: Environmental Microbial & Food Safety Laboratory

Title: Impact of irrigation with wastewater and roof-harvested rainwater on the persistence of Escherichia coli surrogates on lettuce cultivars in the field

Author
item GUPTA, NIDHI - University Of Maryland
item YIN, HSIN-BAI - US Department Of Agriculture (USDA)
item BOOMER, ASHLEY - US Department Of Agriculture (USDA)
item CHEN, CHI-HUNG - US Department Of Agriculture (USDA)
item BYUN, SUYEUN - US Department Of Agriculture (USDA)
item Patel, Jitu

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: 3/19/2019
Publication Date: 7/21/2019
Citation: Gupta, N., Yin, H., Boomer, A., Chen, C., Byun, S., Patel, J.R. 2019. Impact of irrigation with wastewater and roof-harvested rainwater on the persistence of Escherichia coli surrogates on lettuce cultivars in the field. International Association for Food Protection. 2:200.

Interpretive Summary:

Technical Abstract: Introduction: Secondary-treated wastewater (STWW) and roof-harvested rainwater (RHW) may serve as alternative irrigation sources for small growers to decrease the pressure on freshwater. Further investigation is needed to evaluate microbiological safety of fresh produce irrigated with these waters. Purpose: The effect of STWW and RHW on the persistence of Escherichia coli surrogates on different cultivars of lettuce in the field was investigated. Methods: The 4-weeks old, field grown lettuce plants (Annapolis, Celinet, and Coastline cultivars) were spray-irrigated with well water (control), STWW, or RHW containing 5 log CFU/ml of a mixture of non-pathogenic surrogates nalidixic acid-resistant E. coli O157:H12 and chloramphenicol-resistant E. coli K12. On 0, 1, 3, 7 and 10 days-post-irrigation, four replicate lettuce samples (20 g/sample) from each group were collected and pummeled in 80 ml of buffered peptone water for 2 min, followed by plating on Sorbitol MacConkey agar with antibiotics. Results: E. coli H12 persisted at significantly higher level than E. coli K12 on lettuce regardless the water sources and lettuce cultivars. Recovery of H12 and K12 strains on STWW- and RHW-irrigated lettuce was not different from control-irrigated lettuce on day 10; however, H12 populations increased by 1.6 log CFU/g in the RHW- and STWW-irrigated Annapolis lettuce on day 7 compared to the control. The difference in leaf characteristics of lettuce cultivars influenced persistence of these surrogates on leaves. On day 3, the recovery of E. coli H12 on RHW-irrigated Celinet lettuce was significantly higher (3.0 log CFU/g) than E. coli H12 recovered from other two cultivars (1.0 log CFU/g). Listeria monocytogenes and E. coli O157:H7 were not detected in lettuce irrigated with STWW or RHW. Significance: Bacterial pathogens may persist at higher levels on lettuce irrigated with STWW and RHW. The bacterial strains and lettuce cultivars could influence the bacterial persistence on the irrigated lettuce.