Elucidating the Role of Virulence Traits in the Survival of Pathogenic E. coli PI-7 Following Disinfection.

Krishnakumar Sivakumar,Nicolas Augsburger,Jesper Tegner,Andri Taruna Rachmadi,Pei-Ying Hong,Robert Lehmann,Noor Zaouri

doi:10.3389/fbioe.2020.614186

Krishnakumar Sivakumar, Nicolas Augsburger + Show 5 more

Open Access

https://doi.org/10.3389/fbioe.2020.614186

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Abstract

Reuse and discharge of treated wastewater can result in dissemination of microorganisms into the environment. Deployment of disinfection strategies is typically proposed as a last stage remediation effort to further inactivate viable microorganisms. In this study, we hypothesize that virulence traits, including biofilm formation, motility, siderophore, and curli production along with the capability to internalize into mammalian cells play a role in survival against disinfectants. Pathogenic E. coli PI-7 strain was used as a model bacterium that was exposed to diverse disinfection strategies such as chlorination, UV and solar irradiation. To this end, we used a random transposon mutagenesis library screening approach to generate 14 mutants that exhibited varying levels of virulence traits. In these 14 isolated mutants, we observed that an increase in virulence traits such as biofilm formation, motility, curli production, and internalization capability, increased the inactivation half-lives of mutants compared to wild-type E. coli PI-7. In addition, oxidative stress response and EPS production contributed to lengthening the lag phase duration (defined as the time required for exposure to disinfectant prior to decay). However, traits related to siderophore production did not help with survival against the tested disinfection strategies. Taken together, the findings suggested that selected virulence traits facilitate survival of pathogenic E. coli PI-7, which in turn could account for the selective enrichment of pathogens over the non-pathogenic ones after wastewater treatment. Further, the study also reflected on the effectiveness of UV as a more viable disinfection strategy for inactivation of pathogens.

Highlights

Bacterial pathogens can be discharged into raw wastewater through fecal material, and despite going through the wastewater treatment processes, some tend to persist in treated wastewater effluent (Crockett, 2007; Shannon et al, 2007; Naidoo and Olaniran, 2014)
We demonstrated the ability of opportunistic pathogen E. coli PI-7 to survive solar irradiationimposed inactivation more effectively than commercial strain E. coli DSM1103 (Al-Jassim et al, 2017)
Transcriptomic analysis confirmed the upregulation of genes associated with virulence factors, cellular repair and oxidative stress response that facilitated enhanced survival under solar radiation but did not confirm whether virulence factors were playing a role in facilitating persistence (Al-Jassim et al, 2017)

Summary

Introduction

Bacterial pathogens can be discharged into raw wastewater through fecal material, and despite going through the wastewater treatment processes, some tend to persist in treated wastewater effluent (Crockett, 2007; Shannon et al, 2007; Naidoo and Olaniran, 2014). Virulence Influence Persistence Against Disinfection (Blasco et al, 2008; Munir et al, 2011) and are disseminated into the environment to potentially cause infection of living hosts (Naidoo and Olaniran, 2014; Adefisoye and Okoh, 2016). This highlights the requirement for effective strategies to mitigate the dissemination of fecal-borne pathogenic strains from wastewater to the natural environment. Few hours of exposure to simulated sunlight has resulted in rapid inactivation of fecal indicator organisms and waterborne pathogens (Wegelin et al, 1994; McGuigan et al, 1998; Boyle et al, 2008; Ubomba-Jaswa et al, 2009)

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