Survival of Mycobacterium avium, Legionella pneumophila, Escherichia coli, and caliciviruses in drinking water-associated biofilms grown under high-shear turbulent flow.
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.
Lehtola
Markku J
MJ
Environmental Microbiology Laboratory, National Public Health Institute, Department of Environmental Health, P.O. Box 95, FI-70701 Kuopio, Finland. Markku.Lehtola@ktl.fi
Torvinen
Eila
E
Kusnetsov
Jaana
J
Pitkänen
Tarja
T
Maunula
Leena
L
von Bonsdorff
Carl-Henrik
CH
Martikainen
Pertti J
PJ
Wilks
Sandra A
SA
Keevil
C William
CW
Miettinen
Ilkka T
IT
D018441:Biofilms / Q000254:growth & development*; D002139:Caliciviridae / Q000254:growth & development*; D017931:DNA Primers; D004926:Escherichia coli / Q000254:growth & development*; D017404:In Situ Hybridization, Fluorescence; D016952:Legionella pneumophila / Q000254:growth & development*; D009162:Mycobacterium avium / Q000254:growth & development*; D014871:Water Microbiology; D014872:Water Movements; D014881:Water Supply
D017931:DNA Primers