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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 #381940
Research Project: Characterization and Mitigation of Bacterial Pathogens in the Fresh Produce Production and Processing Continuum

Location: Environmental Microbial & Food Safety Laboratory

Title: Pre-harvest biocontrol of Listeria and Escherichia coli O157 on lettuce by lactic acid bacteria

Author
item CHEN, CHI-HUNG - US Department Of Agriculture (USDA)
item YIN, HSINBAI - US Department Of Agriculture (USDA)
item MAYER, CHRISTINE - Wilson College
item Patel, Jitu

Submitted to: International Association for Food Protection Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/26/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Introduction: Recent outbreaks linked to the contaminated lettuce highlight the need for identifying effective natural approaches to improve produce safety at pre-harvest level. Purpose: Efficacy of lactic acid bacteria (LAB) including Lactococcus lactis, Lactobacillus plantarum, Lactobacillus johnsonii, and Lactobacillus acidophilus, as pre-harvest biocontrol against Listeria and E. coli O157 on lettuce grown in field and growth chamber was investigated. Methods: Field grown lettuce cultivars “Green Star” and “New Red Fire” were spray-inoculated with Listeria innocua or E. coli O157:H12 (5 log CFU/g) as non-pathogenic surrogates for Listeria monocytogenes and E. coli O157:H7 a week prior to harvest. Inoculated lettuce plants were spray-treated with water (control) or a mixture of LAB (8 log CFU/g). On 0, 3, and 5 days-post-inoculation (dpi), four samples (20 g/sample) from each group were collected and bacterial populations were determined by spiral plating on selective agars. The experiment was repeated in a growth chamber with “Green Star” lettuce using pathogenic L. monocytogenes and E. coli O157:H7. Results: In field study, LAB significantly reduced E. coli O157:H12 by up to 2.5 log CFU/g on lettuce cultivars on 0 dpi as compared to the control. On 5 dpi, ~ 1 log CFU/g of E. coli O157:H12 were recovered from both LAB-treated lettuce cultivars compared to ~2 log CFU/g recovered from the control (P<0.05). Similarly, LAB reduced ~ 1 log CFU/g of L. innocua populations on “Green Star” lettuce on 3 dpi (P<0.05). Further, 1.5 and 1.0 log CFU/g reductions in L. monocytogenes populations were observed on lettuce grown in growth chamber following LAB treatment on 3 and 5 dpi, respectively (P<0.05). LAB significantly reduced E. coli O157:H7 by 2.2 log CFU/g on 0 dpi. Significance: LAB can be potentially used as pre-harvest biocontrol agents against Listeria and E. coli on lettuce.