[Source: PLoS One, full page: (LINK). Abstract, edited.]
OPEN ACCESS / PEER-REVIEWED / RESEARCH ARTICLE
Investigation of prevalence of free Shiga toxin-producing Escherichia coli (STEC)-specific bacteriophages and its correlation with STEC bacterial hosts in a produce-growing area in Salinas, California
Yen-Te Liao, Irwin A. Quintela, Kimberly Nguyen, Alexandra Salvador, Michael B. Cooley, Vivian C. H. Wu
Published: January 4, 2018 / DOI: https://doi.org/10.1371/journal.pone.0190534
Shiga toxin-producing E. coli (STEC) causes approximately 265,000 illnesses and 3,600 hospitalizations annually and is highly associated with animal contamination due to the natural reservoir of ruminant gastrointestinal tracts. Free STEC-specific bacteriophages against STEC strains are also commonly isolated from fecal-contaminated environment. Previous studies have evaluated the correlation between the prevalence of STEC-specific bacteriophages and STEC strains to improve animal-associated environment. However, the similar information regarding free STEC-specific bacteriophages prevalence in produce growing area is lacking. Thus, the objectives of this research were to determine the prevalence of STEC-specific phages, analyze potential effects of environmental factors on the prevalence of the phages, and study correlations between STEC-specific bacteriophages and the bacterial hosts in pre-harvest produce environment. Surface water from 20 samples sites was subjected to free bacteriophage isolation using host strains of both generic E. coli and STEC (O157, six non-O157 and one O179 strains) cocktails, and isolation of O157 and non-O157 STEC strains by use of culture methods combined with PCR-based confirmation. The weather data were obtained from weather station website. Free O145- and O179-specific bacteriophages were the two most frequently isolated bacteriophages among all (O45, O145, O157 and O179) in this study. The results showed June and July had relatively high prevalence of overall STEC-specific bacteriophages with minimum isolation of STEC strains. In addition, the bacteriophages were likely isolated in the area—around or within city—with predominant human impact, whereas the STEC bacterial isolates were commonly found in agriculture impact environment. Furthermore, there was a trend that the sample sites with positive of free STEC bacteriophage did not have the specific STEC bacterial hosts. The findings of the study enable us to understand the ecology between free STEC-specific phages and STEC bacteria for further pre-harvest food safety management in produce environment.
Citation: Liao Y-T, Quintela IA, Nguyen K, Salvador A, Cooley MB, Wu VCH (2018) Investigation of prevalence of free Shiga toxin-producing Escherichia coli (STEC)-specific bacteriophages and its correlation with STEC bacterial hosts in a produce-growing area in Salinas, California. PLoS ONE 13(1): e0190534. https://doi.org/10.1371/journal.pone.0190534
Editor: A. Mark Ibekwe, USDA-ARS Salinity Laboratory, UNITED STATES
Received: September 12, 2017; Accepted: December 11, 2017; Published: January 4, 2018
This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
Data Availability: The raw data used for both Fig 2 and Fig 3 are within the Supporting Information files. In addition, our findings indicate the isolation of STEC strains, and some sample sites may be in close proximity to farms. Since the data were only used for research purpose and the isolation of STEC strains were likely derived from wild animals, we have requested not to reveal the geographical information. Data queries can be made to the authors, who may be contacted at email@example.com.
Funding: This work was supported by USDA-ARS CRIS projects 2030-42000-050-00D.
Competing interests: The authors have declared that no competing interests exist.
Keywords: Food Safety; STEC; E. Coli; Environmental Pollution; USA; California; Bacteriophages.