Location: Produce Safety and Microbiology ResearchTitle: The Prevalence of Bacteriophages Lytic against Shiga Toxin-Producing Escherichia coli (STEC) and its Correlation with STEC Bacterial Hosts in an Organic Farm
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2019
Publication Date: N/A
Technical Abstract: Lytic bacteriophages are increasingly considered as alternative biocontrol agents of bacterial pathogens due to their killing effect. The majority of the phages specific to enteropathogenic bacteria, such as Shiga toxin-producing E. coli (STEC), have been frequently isolated from animal-associated environments, such as feedlots. However, the information regarding the prevalence of STEC-specific phages in different types of produce farms is scarce. The purpose of this research was to evaluate the prevalence of lytic bacteriophages specific to STEC strains and its correlation with STEC bacterial hosts in an organic farm. Between August 2017 and September 2018, a total of 370 samples, including water, soil, sediment and animal feces, were collected monthly from an organic farm in Northern California containing two separate farming areas: one with and one without animal activity. Cocktails of 3 non-pathogenic E. coli and 14 STEC strains (top six non-O157 and O157 serogroups) were used for phage isolation and host range tests. Culture methods and PCR were used to isolate STEC strains. Information regarding temperature, rain precipitation and solar radiation was also collected. The results showed that 31 (8.4%) of the samples were positive for lytic bacteriophage active against STEC strains. Most bacteriophage-positive samples (n=26) were collected from the areas with animal activity. Spring season, particularly April, had relatively high prevalence of bacteriophages, which was likely due to high rain precipitation. Additionally, the 3 most frequently isolated bacteriophages were lytic against STEC O103, O45, and O121. No phages harbored stx genes in this study. One STEC O103 was isolated; however, no phages specific to the serogroup were isolated from the particular sample. The findings indicate that the prevalence of STEC-specific phages is highly associated with samples collected from the animal-involved areas. Additionally, the presence of these bacteriophages is attributed to the negative correlation with the presence of their STEC hosts.