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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 #337463
Research Project: Characterization and Mitigation of Bacterial Pathogens in the Fresh Produce Production and Processing Continuum

Location: Environmental Microbial & Food Safety Laboratory

Title: Persistence of non-O157 Shiga Toxin-producing Escherichia coli on fresh produce surfaces

Author
item Green, Jennifer
item Patel, Jitu

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: 3/16/2017
Publication Date: 7/6/2017
Citation: Green, J.A., Patel, J.R. 2017. Persistence of non-O157 Shiga Toxin-producing Escherichia coli on fresh produce surfaces. International Association for Food Protection. p.03-67. July 9-12, 2017.

Interpretive Summary:

Technical Abstract: Introduction: The illnesses attributed to non-O157 Shiga toxin-producing Escherichia coli (STEC) have increased in the past decade with 22 foodborne outbreaks associated with non-O157 STEC. Lettuce and salad bars have been implicated in those outbreaks. Prevalence of the six major non-O157 STEC serotypes in agriculture soil and close association with fresh produce requires investigation on their persistence on fresh produce. Purpose: The purpose of this study was to evaluate the persistence of non-O157 STEC on fresh produce surfaces. Methods: Twelve strains of six non-O157 serotypes (O26, O45, O103, O111, O121, O145) were evaluated for curli expression, hydrophobicity, and attachment to fresh produce (cabbage, Romaine lettuce, spinach) leaves. Fresh produce leaves were cut to disc shaped pieces (22-mm dia) and inoculated with 50 µL (10 micro-droplets of 5 µL each) of actively growing cultures. Inoculated fresh produce discs were incubated at 4, 10, and 22°C for 48 h and bacterial populations were analyzed at 0, 1, 4, 24, and 48 h by spiral plating on selective media. Curli expression and cell hydrophobicity was analyzed by Congo red (CR) dye and Bacterial attachment to hydrocarbon (BATH) assay, respectively. Results: Persistence of non-O157 serotypes varied with produce surface and incubation temperature. Recovery of attached STEC was 2-3 log CFU/g lower from their initial populations (~6.5 log CFU/g) when fresh produce was incubated for 24-48 h. Significant reductions in STEC populations were observed when spinach was incubated at 22 °C for 48 h. E. coli O26:H11strain 5711 was recovered at significantly higher level than E. coli O121:H19 strain 5705 on cabbage and Romaine lettuce following 48 h incubation at 4°C. In general, curli-expressing ability of STEC strains didn't influence bacterial attachment. Significance: Persistence of non-O157 serotypes varies among STEC serotypes, produce surface, and incubation temperature. Bacterial attachment on produce surface is a quite complex phenomenon and its knowledge will be helpful in the evaluation of contamination risk during processing and storage of fresh produce.