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Detection of Escherichia coli in biofilms from pipe samples and coupons in drinking water distribution networks

Detection of Escherichia coli in biofilms from pipe samples and coupons in drinking water distribution networks
Detection of Escherichia coli in biofilms from pipe samples and coupons in drinking water distribution networks
Fluorescence in situ hybridization (FISH) was applied for direct detection of Escherichia coli on pipe surfaces and coupons in drinking water distribution networks. Old cast iron main pipes were removed from water distribution networks in France, England, Portugal and Latvia and E. coli was analyzed in the biofilm. In addition, 44 flat coupons made of cast iron, PVC or stainless steel were placed into and continuously exposed to water on 15 locations of 6 distribution networks in France and Latvia and examined after one to six months exposure to the drinking water. In order to increase signal intensity a peptide nucleic acid (PNA) 15-mer probe was used in the FISH screening for the presence or absence of E. coli on the surface of pipes and coupons, thus reducing occasional problems of autofluorescence and low fluorescence of the labeled bacteria. For comparison, cells were removed from the surfaces and examined with culture-based or enzymatic (detection of -D-glucuronidase) methods. An additional verification was made using PCR. Culture method indicated presence of E.coli in 1 out of 5 pipes whereas all pipes were positive with FISH methods. E.coli were detected in 56% of coupons using PNA FISH but no E.coli were detected using culture or enzymatic methods. PCR analyses confirmed the presence of E. coli in samples which were negative according to the culture-based and enzymatic methods. The viability of E. coli cells in the samples was demonstrated by the cell elongation after resuscitation in low nutrient medium supplemented with pipemidic acid, suggesting that the cells were present in an active but non-culturable state (ABNC), unable to grow on agar media. E. coli contributed to approximately 0.001 - 0.1 % of the total bacterial number in the samples. The presence and number of E. coli did not correlate with any of physical and/or chemical characteristic of the drinking water (e.g. temperature, chlorine or biodegradable organic matter concentration).
The study showed that E. coli is present in the biofilms of drinking water networks in Europe. Some of the cells are metabolically active but are often not detected due to limitations of traditionally used culture-based methods, indicating that biofilm should be considered as a reservoir that must be investigated further in order to evaluate the risk for human health.
0099-2240
7456-7464
Juhna, T.
6c6cfef7-4bf1-4db1-8b17-e7c8bc9b39be
Birzniece, D.
ec3e870b-a95c-4e3a-9d21-276ff6a67215
Larsson, S.
8617c357-72b2-4c59-b5cb-63cb96a235b9
Zulenkovs, D.
7831c699-bbab-42d1-bab3-d9198ae347c9
Sharipo, A.
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Azevedo, N.F.
c90d7c41-e45a-404d-9472-9d0b411448e7
Menard-Szczebara, F.
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Castagnet, S.
263aa370-1947-4005-a7ea-7afd22e1fac2
Feliers, C.
2d33a8e5-8889-48d6-8e88-3e9a92e99fd4
Keevil, C.W.
cb7de0a7-ce33-4cfa-af52-07f99e5650eb
Juhna, T.
6c6cfef7-4bf1-4db1-8b17-e7c8bc9b39be
Birzniece, D.
ec3e870b-a95c-4e3a-9d21-276ff6a67215
Larsson, S.
8617c357-72b2-4c59-b5cb-63cb96a235b9
Zulenkovs, D.
7831c699-bbab-42d1-bab3-d9198ae347c9
Sharipo, A.
11bf4da9-582f-4018-91f4-18bfaea30834
Azevedo, N.F.
c90d7c41-e45a-404d-9472-9d0b411448e7
Menard-Szczebara, F.
51ac4759-320f-469f-a23d-945077da298c
Castagnet, S.
263aa370-1947-4005-a7ea-7afd22e1fac2
Feliers, C.
2d33a8e5-8889-48d6-8e88-3e9a92e99fd4
Keevil, C.W.
cb7de0a7-ce33-4cfa-af52-07f99e5650eb

Juhna, T., Birzniece, D., Larsson, S., Zulenkovs, D., Sharipo, A., Azevedo, N.F., Menard-Szczebara, F., Castagnet, S., Feliers, C. and Keevil, C.W. (2007) Detection of Escherichia coli in biofilms from pipe samples and coupons in drinking water distribution networks. Applied and Environmental Microbiology, 73, 7456-7464. (doi:10.1128/AEM.00845-07).

Record type: Article

Abstract

Fluorescence in situ hybridization (FISH) was applied for direct detection of Escherichia coli on pipe surfaces and coupons in drinking water distribution networks. Old cast iron main pipes were removed from water distribution networks in France, England, Portugal and Latvia and E. coli was analyzed in the biofilm. In addition, 44 flat coupons made of cast iron, PVC or stainless steel were placed into and continuously exposed to water on 15 locations of 6 distribution networks in France and Latvia and examined after one to six months exposure to the drinking water. In order to increase signal intensity a peptide nucleic acid (PNA) 15-mer probe was used in the FISH screening for the presence or absence of E. coli on the surface of pipes and coupons, thus reducing occasional problems of autofluorescence and low fluorescence of the labeled bacteria. For comparison, cells were removed from the surfaces and examined with culture-based or enzymatic (detection of -D-glucuronidase) methods. An additional verification was made using PCR. Culture method indicated presence of E.coli in 1 out of 5 pipes whereas all pipes were positive with FISH methods. E.coli were detected in 56% of coupons using PNA FISH but no E.coli were detected using culture or enzymatic methods. PCR analyses confirmed the presence of E. coli in samples which were negative according to the culture-based and enzymatic methods. The viability of E. coli cells in the samples was demonstrated by the cell elongation after resuscitation in low nutrient medium supplemented with pipemidic acid, suggesting that the cells were present in an active but non-culturable state (ABNC), unable to grow on agar media. E. coli contributed to approximately 0.001 - 0.1 % of the total bacterial number in the samples. The presence and number of E. coli did not correlate with any of physical and/or chemical characteristic of the drinking water (e.g. temperature, chlorine or biodegradable organic matter concentration).
The study showed that E. coli is present in the biofilms of drinking water networks in Europe. Some of the cells are metabolically active but are often not detected due to limitations of traditionally used culture-based methods, indicating that biofilm should be considered as a reservoir that must be investigated further in order to evaluate the risk for human health.

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Published date: 1 November 2007

Identifiers

Local EPrints ID: 56546
URI: http://eprints.soton.ac.uk/id/eprint/56546
ISSN: 0099-2240
PURE UUID: 85659df0-dd36-43e5-9a6b-ef239b640c43
ORCID for C.W. Keevil: ORCID iD orcid.org/0000-0003-1917-7706

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Date deposited: 06 Aug 2008
Last modified: 16 Mar 2024 03:24

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Contributors

Author: T. Juhna
Author: D. Birzniece
Author: S. Larsson
Author: D. Zulenkovs
Author: A. Sharipo
Author: N.F. Azevedo
Author: F. Menard-Szczebara
Author: S. Castagnet
Author: C. Feliers
Author: C.W. Keevil ORCID iD

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