The Composition of Microbial Communities in Six Streams, and Its Association With Environmental Conditions, and Foodborne Pathogen Isolation.

Taejung Chung,Jasna Kovac,Daniel L Weller

doi:10.3389/fmicb.2020.01757

Taejung Chung, Jasna Kovac + Show 1 more

Open Access

https://doi.org/10.3389/fmicb.2020.01757

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Abstract

Surface water used for produce production is a potential source of pre-harvest contamination with foodborne pathogens. Decisions on how to mitigate food safety risks associated with pre-harvest water use currently rely on generic Escherichia coli-based water quality tests, although multiple studies have suggested that E. coli levels are not a suitable indicator of the food safety risks under all relevant environmental conditions. Hence, improved understanding of spatiotemporal variability in surface water microbiota composition is needed to facilitate identification of alternative or supplementary indicators that co-occur with pathogens. To this end, we aimed to characterize the composition of bacterial and fungal communities in the sediment and water fractions of 68 agricultural water samples collected from six New York streams. We investigated potential associations between the composition of microbial communities, environmental factors and Salmonella and/or Listeria monocytogenes isolation. We found significantly different composition of fungal and bacterial communities among sampled streams and among water fractions of collected samples. This indicates that geography and the amount of sediment in a collected water sample may affect its microbial composition, which was further supported by identified associations between the flow rate, turbidity, pH and conductivity, and microbial community composition. Lastly, we identified specific microbial families that were weakly associated with the presence of Salmonella or Listeria monocytogenes, however, further studies on samples from additional streams are needed to assess whether identified families may be used as indicators of pathogen presence.

Highlights

In 2015, United States agriculture used over 118 million gallons of water per day for irrigation, with more than half of all withdrawals originating from surface water sources (Dieter et al, 2018)
Insufficient amount of DNA was obtained from 22 water fraction samples, resulting in no PCR amplification
This study provides baseline data characterizing bacterial and fungal microbial communities in New York agricultural water

Summary

Introduction

In 2015, United States agriculture used over 118 million gallons of water per day for irrigation, with more than half of all withdrawals originating from surface water sources (Dieter et al, 2018). One of the examples is a high-profile E. coli O157:H7 outbreak in 2018 associated with romaine lettuce that resulted in 62 cases of foodborne illness, including 25 hospitalizations (FDA, 2019b) During this outbreak investigation, the outbreak strain was detected in a sediment sample from a reservoir that provided water to the implicated farms, suggesting that the agricultural water may have been a potential source of contamination (Gelting et al, 2011; Mody et al, 2011; FDA, 2019b). The outbreak strain was detected in a sediment sample from a reservoir that provided water to the implicated farms, suggesting that the agricultural water may have been a potential source of contamination (Gelting et al, 2011; Mody et al, 2011; FDA, 2019b) This and other multistate foodborne disease outbreaks associated with fresh produce have increased concerns related to the use of surface water for produce production and processing (Gelting et al, 2011)

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