Irrigation Method Matters: Contamination and Die-off Rates of Escherichia coli on Dry Bulb Onions After Overhead and Drip Irrigation in Washington State (2022-2023)
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View abstract on PubMed
Summary
This summary is machine-generated.Field trials investigated Escherichia coli (E. coli) survival on dry bulb onions after contaminated irrigation. Drip irrigation posed a limited risk, while overhead irrigation showed higher contamination, decreasing significantly after curing.
Area Of Science
- Food safety
- Microbiology
- Agricultural science
Background
- Two U.S. outbreaks of salmonellosis in 2020 and 2021 were linked to red onions.
- Agricultural water was implicated as a potential contamination source in the 2020 outbreak.
Purpose Of The Study
- To investigate the prevalence and survival of Escherichia coli (E. coli), a surrogate for Salmonella, on dry bulb onions.
- To assess contamination risks associated with different irrigation methods (drip vs. overhead) using contaminated water at the end of the growing season.
Main Methods
- Field trials applied inoculated irrigation water (containing rifampin-resistant E. coli) to onions.
- Onion bulbs were sampled immediately after irrigation and during a 4-week field curing period.
- E. coli was enumerated using the most probable number (MPN) method.
Main Results
- Drip irrigation showed limited E. coli detection (13% at 24h with 3 log MPN/100mL), increasing with saturated soil (63% at 0h with 5 log MPN/100mL).
- Overhead irrigation resulted in high E. coli prevalence (98-100% at 0h).
- E. coli prevalence significantly decreased after 7 days of field curing for both irrigation methods.
Conclusions
- Drip irrigation presents a limited risk for onion contamination from agricultural water.
- Overhead irrigation poses a higher contamination risk, emphasizing the importance of water quality and curing practices.
- Field curing significantly reduces E. coli prevalence on onions, regardless of irrigation method.
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