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Water 2018, 10(9), 1219; https://doi.org/10.3390/w10091219

Searching for Activity Markers that Approximate (VBNC) Legionella pneumophila Infectivity in Amoeba after Ultraviolet (UV) Irradiation

School of Public Health, University of Alberta, 3-57 South Academic Building, Edmonton, AB T6G 2G7, Canada
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Received: 7 August 2018 / Revised: 4 September 2018 / Accepted: 7 September 2018 / Published: 10 September 2018
(This article belongs to the Section Water and Wastewater Treatment)
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Abstract

Legionella pneumophila is an increasingly recognized threat to public health via aerosol exposures; with a variety of control measures including: water temperature/flow management and free chlorine used to reduce the risk of infection within healthcare centers. Despite these efforts, L. pneumophila often recolonizes plumbing systems after specific treatments, which prompted us to examine ultraviolet (UV) irradiation for a point-of-use, secondary control measure. Currently, there is no data on the efficacy of high (>254 nm) wavelength UV-C (100–280 nm) light inactivation of L. pneumophila with resuscitation of viable but non-culturable (VBNC) cells. We report for the first time L. pneumophila dose-responses for 268.6 nm and 288.6 nm UV-C, as compared to 256 nm, and demonstrate UV induced VBNC L. pneumophila remaining infectious to Acanthamoeba polyphaga during co-culture experiments. Findings were correlated to molecular-based activity assays to identify additional measures of L. pneumophila viability following UV disinfection compared to culture. A collection of viability markers may provide a more representative measure of risk compared to current culture-based detection, since UV-C irradiated L. pneumophila lose culturability, yet retain activity, increased ATP production, and the ability to be resuscitated by amoeba co-culture. This finding is significant as it identifies potential concern from VBNC cells following UV-C disinfection and the need for further research into the efficacy of UV inactivation as a point-of-use application for L. pneumophila control and management. View Full-Text
Keywords: Legionella; UV inactivation; viable but non-culturable (VBNC); amoeba; resuscitation; activity assay; flow cytometry Legionella; UV inactivation; viable but non-culturable (VBNC); amoeba; resuscitation; activity assay; flow cytometry
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Grossi, M.R.; Dey, R.; Ashbolt, N.J. Searching for Activity Markers that Approximate (VBNC) Legionella pneumophila Infectivity in Amoeba after Ultraviolet (UV) Irradiation. Water 2018, 10, 1219.

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