Characterization of Shiga toxin-producing Escherichia coli bacteriophages isolated from agricultural environments and examination of their prevalence with bacterial hosts

Authors: Quintela, Irwin; VALENTINE, DON - University Of Maine; HWANG, ANYA - Volunteer; VASSE, TYLER - Volunteer; HO, KAN-JU - Forest Service (FS); Wu, Vivian

Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2023
Publication Date: 8/30/2023
Citation: Quintela, I.A., Valentine, D.C., Hwang, A., Vasse, T., Ho, K., Wu, V.C. 2023. Characterization of Shiga toxin-producing Escherichia coli bacteriophages isolated from agricultural environments and examination of their prevalence with bacterial hosts. Journal of Food Safety. Article e13084. https://doi.org/10.1111/jfs.13084.
DOI: https://doi.org/10.1111/jfs.13084

Interpretive Summary: Bacteriophages are natural bacterial predators, thus can provide non-antibiotic options to reduce the incidence of foodborne pathogen contamination such as Shiga toxin-producing Escherichia coli (STEC) . In addition, rapid detection technologies can also take advantage of each bacteriophage-host recognition stage and infection pathway to cover a broader range of foodborne pathogen targets. Information specifically on the correlation of the prevalence of STEC bacteriophages with its bacterial hosts and the dynamics of its seasonal populations are currently limited. This study aimed to isolate STEC-specific bacteriophages from cow manure and water trough samples and determine its concurrent prevalence and distribution patterns with STEC serogroups hosts. It was found that the majority of the isolated bacteriophages did not possess virulence genes; therefore they did not pose threats of possible horizontal genes transfer to its host bacteria. In the natural environment, such as in the cattle farms, a heterogenous bacteriophage population is likely more effective in controlling and inhibiting its host population as compared to its homogenous counterpart. Last, purified bacteriophages were highly stable and infective for potential biocontrol and biosensor applications.

Technical Abstract: In the natural environment, ruminant livestock, including cattle, are the main reservoir of outbreak – causing strains of Shiga toxin-producing Escherichia coli (STEC), where bacteriophages sustainably thrive as well. This study focuses on the characterization of STEC-specific bacteriophages isolated from cow manure samples in Maine farms and examines their prevalence with STEC hosts. Phenotypic features of representative isolates were characterized by using a transmission electron microscope. Similarly, host range, one-step growth curve, thermal stability, lytic capability, and genomic analyses were performed to fully characterize selected representative isolates. Results showed that representative bacteriophage isolate belong to Myoviridae (S6P10 and S14P12) and Siphoviridae (S19). The most prevalent and common bacteriophages (46%) were specific to O26 serogroup. Farm C sampling site had highly heterogenous bacteriophage populations that were specific to six STEC serogroups. The most prevalent bacteriophage isolate (S1P5, Escherichia phage vB_EcoM-S1P5QW) was verified to have a double-stranded DNA genome (166,102 bp) with 266 CDs of which 130 have known functions. The majority of the diverse bacteriophage isolates had strong lytic capabilities and narrow host range that can withstand selected temperature conditions (-20°C, 37°C, and 62°C). Results of bacterial screening showed that STEC host strains were not detected in Farms A, C, and E, but were detected on Farms B and D. In conclusion, the highly-diverse bacteriophage ecology found in cow manure samples may have been an important element in shaping the population of STEC serogroups, specifically in its natural environment, which can provide useful tools for potential antibiotic-free therapeutics and diagnostic technologies.