Interaction between Fungal Communities, Soil Properties, and the Survival of Invading E. coli O157:H7 in Soils.

Guannan Huang,Lu Lu,Liyue Zhu,Jiafen Liao,Jincai Ma,Yuang Xie,Ziming Han,Jiahang Li,Guangze Lyu

doi:10.3390/ijerph17103516

Abstract

Pathogens that invade into the soil cancontaminate food and water, andinfect animals and human beings. It is well documented that individual bacterial phyla are well correlated with the survival of E. coliO157 (EcO157), while the interaction betweenthe fungal communities and EcO157 survival remains largely unknown. In this study, soil samples from Tongliao, Siping, and Yanji in northeast China were collected and characterized. Total DNA was extracted for fungal and bacterial community characterization. EcO157 cells were spiked into the soils, and their survival behavior was investigated. Results showed that both fungal and bacterial communities were significantly correlated (p < 0.01) with the survival of EcO157 in soils, and the relative abundances of fungal groups (Dothideomycetes and Sordariomycetes) and some bacterial phyla (Acidobacteria, Firmicutes, gamma- and delta-Proteobacteria)weresignificantly correlated with ttds (p < 0.01). Soil pH, EC (electric conductance) salinity, and water-soluble nitrate nitrogen were significantly correlated with survival time (time to reach the detection limit, ttd) (p < 0.05). The structural equation model indicated that fungal communities could directly influence ttds, and soil properties could indirectly influence the ttds through fungal communities. The first log reduction time (δ) was mainly correlated with soil properties, while the shape parameter (p) was largely correlated with fungal communities. Our data indicated that both fungal and bacterial communities were closely correlated (p < 0.05)with the survival of EcO157 in soils, and different fungal and bacterial groups might play different roles. Fungal communities and bacterial communities explained 5.87% and 17.32% of the overall variation of survival parameters, respectively. Soil properties explained about one-third of the overall variation of survival parameters. These findings expand our current understanding of the environmental behavior of human pathogens in soils.

Highlights

Concerns about E. coli O157:H7 (EcO157) began with an outbreak of food-borne illness in the United States in 1982 [1].In the following years, more cases of E. coliO157 (EcO157) infectionshave been reported worldwide [2]
Our results showed that the soil fungal communitymatrixwas significantly correlated with the survival behavior matrix of EcO157 in soil (Table 2), and different fungal groups exerted different influences on the survival parameters of EcO157 (Figure 6), indicating that overall fungal community has a direct effect on the survival of
Our results show that overall fungal communitiesare significantly correlated with the overall survival of EcO157 in soils, they only explain a relatively small fraction of the overall variation of survival parameters of EcO157 in soils compared with bacterial communities

Summary

Introduction

Concerns about E. coli O157:H7 (EcO157) began with an outbreak of food-borne illness in the United States in 1982 [1].In the following years, more cases of EcO157 infectionshave been reported worldwide [2]. It was suggested that undercooked beef was the main cause of EcO157 infection [3]. Res. Public Health 2020, 17, 3516; doi:10.3390/ijerph17103516 www.mdpi.com/journal/ijerph

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Conclusion