Differential survival of non-O157 Shiga-toxigenic Escherichia coli serotypes in manure-impacted water

Authors: Durso, Lisa; Miller, Daniel; Gilley, John

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2021
Publication Date: 7/9/2021
Citation: Durso, L.M., Miller, D.N., Gilley, J.E. 2021. Differential survival of non-O157 Shiga-toxigenic Escherichia coli serotypes in manure-impacted water. Foodborne Pathogens and Disease. 2021. https://doi.org/10.1089/fpd.2021.0024.
DOI: https://doi.org/10.1089/fpd.2021.0024

Interpretive Summary: There are many factors that impact whether or not pathogenic Shiga-toxigenic Escherichia coli (STEC) from animals can make people sick. One main consideration is that the bacteria has to be transported in some way from the animal, into a human. For STEC this happens often by consuming contaminated food, or by ingesting contaminated water. The second consideration is that the bacteria must survive outside of the animal long enough to make the journey via food or water. If the bacteria dies before it is ingested, then it no longer poses a threat. As part of their natural life-cycle, Shiga toxigenic Escherichia coli (STEC) that are excreted in the feces of wildlife or grazing food animals persist in the environment until they die, or they recolonize a new host. Surface waters contaminated with manure-borne STEC can infect humans via drinking and recreational water use, or when used to irrigate crops that are consumed raw or minimally cooked. Environmental survival time is an important element when evaluating the potential risk of adverse health outcomes from foodborne pathogens. The is a solid body of literature examining the survival of STEC O157 under various conditions in the natural environment outside of the host. While early STEC outbreaks were primarily associated with STEC O157 and with beef and cattle production systems, today non-O157 STEC outbreak cases in the U.S. outnumber STEC O157 cases, and in 2018 -2019 CDC reported twice as many lettuce-associated STEC outbreaks as beef-associated STEC outbreaks. However, data characterizing non-O157 STEC survival and survival potential is sparse and inconsistent. Using manure-impacted water microcosms, the survival of individual STEC strains representing seven serotypes was assessed, along with persistence of target genes. Serotype-specific survival results were observed. STEC O26 and O45 initially grew following inoculation into the manure-impacted water microcosms and remained culturable at the month twelve sampling point. Triplicate samples from the year one replicate remained culturable at 24 months. In contrast, STEC O111, O121 and O145 decreased immediately upon inoculation into the simulated runoff and culturable populations declined below enumerable levels before the end of the study. Microcosm results from this study showed that some STEC serotypes have the biological potential to survive in manure-impacted waters for extended periods of time. There appears to be non-random, serotype-specific differences in survival of target bacteria and persistence of target genes in this set of samples, with STEC O26 and O45 strains appearing to be the most environmentally robust. Results presented here from manure-impacted water microcosms support conclusions from studies in soils and food, indicating that there are serotype-specific differences in survival of STEC cells and persistence of STEC-specific genes in the natural environment.

Technical Abstract: As part of their natural life-cycle, Shiga toxigenic Escherichia coli (STEC) that are excreted in feces persist in the environment until they die, or they recolonize a new host. Surface waters contaminated with manure-borne STEC can infect humans via drinking and recreational water use, or when used to irrigate crops that are consumed raw or minimally cooked. Environmental survival time is an important element when evaluating the potential risk of adverse health outcomes from foodborne pathogens. The is a solid body of literature examining the survival of STEC O157 under various conditions in the natural environment outside of the host. However, data characterizing non-O157 STEC survival and survival potential is sparse and inconsistent. Using manure-impacted water microcosms, the survival of individual STEC strains representing seven serotypes was assessed, along with persistence of target genes. Serotype-specific survival results were observed. STEC O26 and O45 initially grew following inoculation into the manure-impacted water microcosms and remained culturable at the month twelve sampling point. Triplicate samples from the year one replicate remained culturable at 24 months. In contrast, STEC O111, O121 and O145 decreased immediately upon inoculation into the simulated runoff and culturable populations declined below enumerable levels before the end of the study. Microcosm results from this study showed that some STEC serotypes have the biological potential to survive in manure-impacted waters for extended periods of time. There appears to be non-random, serotype-specific differences in survival of target bacteria and persistence of target genes in this set of samples, with STEC O26 and O45 strains appearing to be the most environmentally robust. Results presented here from manure-impacted water microcosms support conclusions from studies in soils and food, indicating that there are serotype-specific differences in survival of STEC cells and persistence of STEC-specific genes in the natural environment.