Bacteriophages Are Good Estimators of Human Viruses Present in Water.

Elisenda Ballesté,Javier Mendez,Leena Maunula,Andreas H Farnleitner,Joan Jofre,Andreas Tiehm,Laura Sala-Comorera,Silvia Monteiro,Cristina García-Aljaro,Anicet R Blanch

doi:10.3389/fmicb.2021.619495

Abstract

The detection of fecal viral pathogens in water is hampered by their great variety and complex analysis. As traditional bacterial indicators are poor viral indicators, there is a need for alternative methods, such as the use of somatic coliphages, which have been included in water safety regulations in recent years. Some researchers have also recommended the use of reference viral pathogens such as noroviruses or other enteric viruses to improve the prediction of fecal viral pollution of human origin. In this work, phages previously tested in microbial source tracking studies were compared with norovirus and adenovirus for their suitability as indicators of human fecal viruses. The phages, namely those infecting human-associated Bacteroides thetaiotaomicron strain GA17 (GA17PH) and porcine-associated Bacteroides strain PG76 (PGPH), and the human-associated crAssphage marker (crAssPH), were evaluated in sewage samples and fecal mixtures obtained from different animals in five European countries, along with norovirus GI + GII (NoV) and human adenovirus (HAdV). GA17PH had an overall sensitivity of ≥83% and the highest specificity (>88%) for human pollution source detection. crAssPH showed the highest sensitivity (100%) and specificity (100%) in northern European countries but a much lower specificity in Spain and Portugal (10 and 30%, respectively), being detected in animal wastewater samples with a high concentration of fecal indicators. The correlations between GA17PH, crAssPH, or the sum of both (BACPH) and HAdV or NoV were higher than between the two human viruses, indicating that bacteriophages are feasible indicators of human viral pathogens of fecal origin and constitute a promising, easy to use and affordable alternative to human viruses for routine water safety monitoring.

Highlights

To date, over 150 human enteric viruses have been detected in water bodies (Rodríguez-Lázaro et al, 2012; Tran et al, 2015; Farkas et al, 2019), including adenoviruses, noroviruses, enteroviruses, sapoviruses, rotaviruses, and polyomaviruses, among others
We assessed the suitability of human viruses (NoV and HadV) as markers of fecal viral pollution
human adenovirus (HAdV) was detected in 60% of the human sewage samples, norovirus GI + GII (NoV) in 80%, GA17PH in 91%, and crAssphage marker (crAssPH) in 100%, indicating that the bacteriophage markers were more sensitive than the enteric viruses

Summary

Introduction

Over 150 human enteric viruses have been detected in water bodies (Rodríguez-Lázaro et al, 2012; Tran et al, 2015; Farkas et al, 2019), including adenoviruses, noroviruses, enteroviruses, sapoviruses, rotaviruses, and polyomaviruses, among others. The monitoring of reference viruses such as NoV and human adenovirus (HAdV) has been proposed (Hundesa et al, 2006; Ahmed et al, 2010; Rusiñol et al, 2014; Mayer et al, 2016). Enteroviruses are the most detectable enteric viruses by cell culture, and have been considered as potential indicators of the human enteric viruses (Grabow, 2007). Since the advent of genomic techniques, genome fragments of enteric viruses excreted by humans and animals have been proposed as potential viral indicators (Hot et al, 2003; Albinana-Gimenez et al, 2009; Hunt et al, 2010; Silva et al, 2011; Wong et al, 2012). Viruses that exclusively infect humans, such as HAdV, have been postulated as microbial source tracking (MST) markers (Hundesa et al, 2006; Ahmed et al, 2010; Rusiñol et al, 2014)

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