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Validation of SYTO 9/propidium iodide uptake for rapid detection of viable but noncultivable legionella pneumophila

Validation of SYTO 9/propidium iodide uptake for rapid detection of viable but noncultivable legionella pneumophila
Validation of SYTO 9/propidium iodide uptake for rapid detection of viable but noncultivable legionella pneumophila
Legionella pneumophila is an ubiquitous environmental microorganism that can cause Legionnaires' disease or Pontiac fever. As a waterborne pathogen, it has been found to be resistant to chlorine disinfection and survive in drinking water systems, leading to potential outbreaks of waterborne disease. In this work, the effect of different concentrations of free chlorine was studied (0.2, 0.7, and 1.2 mg l(-1)), the cultivability of cells assessed by standard culture techniques (buffered charcoal yeast extract agar plates) and viability using the SYTO 9/propidium iodide fluorochrome uptake assay (LIVE/DEAD BacLight). Results demonstrate that L. pneumophila loses cultivability after exposure for 30 min to 0.7 mg l(-1) of free chlorine and in 10 min when the concentration is increased to 1.2 mg l(-1). However, the viability of the cells was only slightly affected even after 30 min exposure to the highest concentration of chlorine; good correlation was obtained between the rapid SYTO 9/propidium iodide fluorochrome uptake assay and a longer cocultivation with Acanthamoeba polyphaga assay, confirming that these cells could still recover their cultivability. These results raise new concerns about the assessment of drinking water disinfection efficiency and indicate the necessity of further developing new validated rapid methods, such as the SYTO 9/propidium iodide uptake assay, to assess viable but noncultivable L. pneumophila cells in the environment.

0095-3628
56-62
Gião, Maria S.
5638b770-3681-48b2-a9ae-9152b36ac504
Wilks, Sandra A.
86c1f41a-12b3-451c-9245-b1a21775e993
Azevedo, N.F.
c90d7c41-e45a-404d-9472-9d0b411448e7
Vieira, M.J.
b13909e0-b086-49fc-b589-3fb9d2a02577
Keevil, Charles W.
cb7de0a7-ce33-4cfa-af52-07f99e5650eb
Gião, Maria S.
5638b770-3681-48b2-a9ae-9152b36ac504
Wilks, Sandra A.
86c1f41a-12b3-451c-9245-b1a21775e993
Azevedo, N.F.
c90d7c41-e45a-404d-9472-9d0b411448e7
Vieira, M.J.
b13909e0-b086-49fc-b589-3fb9d2a02577
Keevil, Charles W.
cb7de0a7-ce33-4cfa-af52-07f99e5650eb

Gião, Maria S., Wilks, Sandra A., Azevedo, N.F., Vieira, M.J. and Keevil, Charles W. (2009) Validation of SYTO 9/propidium iodide uptake for rapid detection of viable but noncultivable legionella pneumophila. Microbial Ecology, 58 (1), 56-62. (doi:10.1007/s00248-008-9472-x). (PMID:19043657)

Record type: Article

Abstract

Legionella pneumophila is an ubiquitous environmental microorganism that can cause Legionnaires' disease or Pontiac fever. As a waterborne pathogen, it has been found to be resistant to chlorine disinfection and survive in drinking water systems, leading to potential outbreaks of waterborne disease. In this work, the effect of different concentrations of free chlorine was studied (0.2, 0.7, and 1.2 mg l(-1)), the cultivability of cells assessed by standard culture techniques (buffered charcoal yeast extract agar plates) and viability using the SYTO 9/propidium iodide fluorochrome uptake assay (LIVE/DEAD BacLight). Results demonstrate that L. pneumophila loses cultivability after exposure for 30 min to 0.7 mg l(-1) of free chlorine and in 10 min when the concentration is increased to 1.2 mg l(-1). However, the viability of the cells was only slightly affected even after 30 min exposure to the highest concentration of chlorine; good correlation was obtained between the rapid SYTO 9/propidium iodide fluorochrome uptake assay and a longer cocultivation with Acanthamoeba polyphaga assay, confirming that these cells could still recover their cultivability. These results raise new concerns about the assessment of drinking water disinfection efficiency and indicate the necessity of further developing new validated rapid methods, such as the SYTO 9/propidium iodide uptake assay, to assess viable but noncultivable L. pneumophila cells in the environment.

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More information

e-pub ahead of print date: 29 November 2008
Published date: July 2009

Identifiers

Local EPrints ID: 157021
URI: http://eprints.soton.ac.uk/id/eprint/157021
ISSN: 0095-3628
PURE UUID: 4ae336e1-a2c9-416f-b2f0-e7e3081d1944
ORCID for Sandra A. Wilks: ORCID iD orcid.org/0000-0002-4134-9415
ORCID for Charles W. Keevil: ORCID iD orcid.org/0000-0003-1917-7706

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Date deposited: 03 Jun 2010 11:40
Last modified: 14 Mar 2024 02:46

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Contributors

Author: Maria S. Gião
Author: Sandra A. Wilks ORCID iD
Author: N.F. Azevedo
Author: M.J. Vieira

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