Development of a Robust Method for Isolation of Shiga Toxin-Positive Escherichia coli (STEC) from Fecal, Plant, Soil and Water Samples from a Leafy Greens Production Region in California

Michael B. Cooley, Michele T Jay-Russell, Edward R Atwill, Diana Carychao, Kimberly Nguyen, Beatriz Quiñones, Ronak Patel, Samarpita Walker, Michelle Swimley, Edith Pierre-Jerome, Andrew G. Gordus, Robert E. Mandrell

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58 Scopus citations

Abstract

During a 2.5-year survey of 33 farms and ranches in a major leafy greens production region in California, 13,650 produce, soil, livestock, wildlife, and water samples were tested for Shiga toxin (stx)-producing Escherichia coli (STEC). Overall, 357 and 1,912 samples were positive for E. coli O157:H7 (2.6%) or non-O157 STEC (14.0%), respectively. Isolates differentiated by O-typing ELISA and multilocus variable number tandem repeat analysis (MLVA) resulted in 697 O157:H7 and 3,256 non-O157 STEC isolates saved for further analysis. Cattle (7.1%), feral swine (4.7%), sediment (4.4%), and water (3.3%) samples were positive for E. coli O157:H7; 7/32 birds, 2/145 coyotes, 3/88 samples from elk also were positive. Non-O157 STEC were at approximately 5-fold higher incidence compared to O157 STEC: cattle (37.9%), feral swine (21.4%), birds (2.4%), small mammals (3.5%), deer or elk (8.3%), water (14.0%), sediment (12.3%), produce (0.3%) and soil adjacent to produce (0.6%). stx1, stx2 and stx1/stx2 genes were detected in 63%, 74% and 35% of STEC isolates, respectively. Subtilase, intimin and hemolysin genes were present in 28%, 25% and 79% of non-O157 STEC, respectively; 23% were of the "Top 6″ O-types. The initial method was modified twice during the study revealing evidence of culture bias based on differences in virulence and O-antigen profiles. MLVA typing revealed a diverse collection of O157 and non-O157 STEC strains isolated from multiple locations and sources and O157 STEC strains matching outbreak strains. These results emphasize the importance of multiple approaches for isolation of non-O157 STEC, that livestock and wildlife are common sources of potentially virulent STEC, and evidence of STEC persistence and movement in a leafy greens production environment.

Original languageEnglish (US)
Article numbere65716
JournalPLoS One
Volume8
Issue number6
DOIs
StatePublished - Jun 6 2013

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

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    Cooley, M. B., Jay-Russell, M. T., Atwill, E. R., Carychao, D., Nguyen, K., Quiñones, B., Patel, R., Walker, S., Swimley, M., Pierre-Jerome, E., Gordus, A. G., & Mandrell, R. E. (2013). Development of a Robust Method for Isolation of Shiga Toxin-Positive Escherichia coli (STEC) from Fecal, Plant, Soil and Water Samples from a Leafy Greens Production Region in California. PLoS One, 8(6), [e65716]. https://doi.org/10.1371/journal.pone.0065716