FRNA Bacteriophages as Viral Indicators of Faecal Contamination in Mexican Tropical Aquatic Systems

Abstract

A particular challenge to water safety in populous intertropical regions is the lack of reliable faecal indicators to detect microbiological contamination of water, while the numerical relationships of specific viral indicators remain largely unexplored. The aim of this study was to investigate the numerical relationships of FRNA-bacteriophage genotypes, adenovirus 41, and human adenoviruses (HADV) in Mexican surface water systems to assess sewage contamination. We studied the presence of HADV, HADV41 and FRNA bacteriophage genotypes in water samples and quantified by qPCR and RT-qPCR. Virus and water quality indicator variances, as analyzed by principal component analysis and partial least squared regression, followed along the major percentiles of water faecal enterococci. FRNA bacteriophages adequately deciphered viral and point source water contamination. The strongest correlation for HADV was with FRNA bacteriophage type II, in water samples higher than the 50th percentiles of faecal enterococci, thus indicating urban pollution. FRNA bacteriophage genotypes I and III virus indicator performances were assisted by their associations with electrical conductivity and faecal enterococci. In combination, our methods are useful for inferring water quality degradation caused by sewage contamination. The methods used have potential for determining source contamination in water and, specifically, the presence of enteric viruses where clean and contaminated water have mixed.

Fig 1. Log number of the distribution of faecal indicators from tropical water samples.

Fig 2. Principal component analysis bi-plot showing dispersion of vector physicochemical parameters, faecal enterococci, and FRNA bacteriophages I and III among tropical water samples.

Fig 3. Principal component analysis bi-plot showing the vector proximity for the physicochemical, faecal enterococci, FRNA bacteriophages genotype II, human adenovirus, and adenovirus 41 among selected tropical water samples.

Fig 4. Principal component analysis bi-plot showing the vector proximity for the FRNA bacteriophages genotypes, along with the reduced variance for human adenovirus and human adenovirus 41 in higher than 50^th percentile faecal enterococci percentiles in the tropical water samples.