Survival of Mycobacterium avium , Legionella pneumophila , Escherichia coli , and Caliciviruses in Drinking Water-Associated Biofilms Grown under High-Shear Turbulent Flow

Abstract

Most of the bacteria in drinking water distribution systems are associated with biofilms. In biofilms, their nutrient supply is better than in water, and biofilms can provide shelter against disinfection. We used a Propella biofilm reactor for studying the survival of Mycobacterium avium, Legionella pneumophila, Escherichia coli, and canine calicivirus (CaCV) (as a surrogate for human norovirus) in drinking water biofilms grown under high-shear turbulent-flow conditions. The numbers of M. avium and L. pneumophila were analyzed with both culture methods and with peptide nucleic acid fluorescence in situ hybridization (FISH) methods. Even though the numbers of pathogens in biofilms decreased during the experiments, M. avium and L. pneumophila survived in biofilms for more than 2 to 4 weeks in culturable forms. CaCV was detectable with a reverse transcription-PCR method in biofilms for more than 3 weeks. E. coli was detectable by culture for only 4 days in biofilms and 8 days in water, suggesting that it is a poor indicator of the presence of certain waterborne pathogens. With L. pneumophila and M. avium, culture methods underestimated the numbers of bacteria present compared to the FISH results. This study clearly proved that pathogenic bacteria entering water distribution systems can survive in biofilms for at least several weeks, even under conditions of high-shear turbulent flow, and may be a risk to water consumers. Also, considering the low number of virus particles needed to result in an infection, their extended survival in biofilms must be taken into account as a risk for the consumer.

Opportunistic pathogens enriched in showerhead biofilms

“…The reasons for the enrichment of mycobacteria are not clear. Mycobacteria readily form biofilms and, because of their generally waxy quality, may be particularly resistant to shear forces generated in shower operation (28)(29)(30)(31)(32)(33)(34)(35)(36). Furthermore, many species of biofilm-forming mycobacteria are chlorineresistant, and thus potentially can be enriched by chlorine disinfection protocols used by many municipalities (28,29,34,37,38).…”

Mycobacteria in water, soil, plants and air: a review

“…They concluded that culture examination seriously underestimates the occurrence of M. avium in biofilms and water. The study performed by Lehtola et al (2007) clearly proved that pathogenic bacteria entering water distribution systems can survive in biofilms for at least several weeks, even under conditions of high-shear turbulent flow, and may be a risk to water consumers. In order to understand microbial communities in drinking water biofilms, Liu et al (2012) sequenced 16S rRNA in three faucet biofilms using 454-pyrosequencing.…”

Diagnóstico del agua utilizada en las procesadoras de café del Municipio Caripe – Estado Monagas, Venezuela.// Diagnosis of the water used in coffee processors of the Caripe Municipality - Monagas State, Venezuela

“…Sin embargo, puede suceder que algún desagüe de alcantarilla de aguas negras pueda estar en las proximidades de las redes de distribución, las cuales también podrían presentar problemas de corrosión originados por el desarrollo de biopelículas microbianas, dentro de las superficies internas de las tuberías, que favorecen situaciones como la multiplicación de una diversidad de microorganismos patógenos oportunistas (Lehtola et al, 2007), que pueden sobrevivir dentro de las mismas originando cambios que deterioran la seguridad del agua potabilizada en cuanto a coloración (Husband et al, 2008), olor y sabor (Szewzyk et al, 2000;Hallan et al, 2001) y producción de toxinas (Hageskal et al, 2007;Siqueira et al, 2013), debido principalmente a la falta de desinfección o a fallas para proveer los niveles apropiados de cloro (Lee y Schwab, 2005); donde la normativa venezolana recomienda una concentración de 0,5 mg/L (GORV, 1998), lo cual es bastante difícil de manejar en las aguas de las redes de distribución poblacional (Munavalli y Mohan-Kumar, 2005).…”