DVC-FISH to identify potentially pathogenic Legionella inside free-living amoebae from water sources

• Published in: Environmental research Vol. 176; p. 108521
• Main Authors: Moreno, Y., Moreno-Mesonero, L., García-Hernández, J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01.09.2019
• Subjects: Amoeba; Drinking water; DVC-FISH; Environmental Monitoring; Free-living amoebae; Legionella; Legionella pneumophila; Legionella spp; Waste Water; Wastewater; Water Microbiology; Water Supply; Drinking water; Legionella spp; DVC-FISH; Wastewater; Free-living amoebae
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2019.06.002

Despite all safety efforts, drinking and wastewater can still be contaminated by Legionella and free-living amoebae (FLA) since these microorganisms are capable of resisting disinfection treatments. An amoebae cyst harboring pathogenic Legionella spp. can be a transporter of this organism, protecting it and enhancing its infection abilities. Therefore, the aim of this work is to identify by DVC-FISH viable Legionella spp and Legionella pneumophila cells inside FLA from water sources in a specific and rapid way with the aim of assessing the real risk of these waters. A total of 55 water samples were processed, 30 reclaimed wastewater and 25 drinking water. FLA presence was detected in 52.7% of the total processed water samples. When DVC-FISH technique was applied, the presence of viable internalized Legionella spp. cells was identified in 69.0% of the total FLA-positive samples, concretely in 70.0% and 66.7% of wastewater and drinking water samples, respectively. L. pneumophila was simultaneously identified in 48.3% of the total FLA-positive samples, specifically in 50.0% and 44.4% of wastewater and drinking water samples, respectively. By culture, potentially pathogenic Legionella cells were recovered in 27.6% of the total FLA-positive bacteria, particularly in 35.0% and 11.1% of wastewater and drinking water samples, respectively. These findings demonstrate that FLA may promote resistance of bacteria to the performed disinfection treatments for drinking as well as for wastewater. So, in addition to the risk for the presence of pathogenic FLA in water it is necessary to take into account that these can be transporters of the pathogenic bacteria Legionella, which are able to survive inside them. The DVC-FISH method described here has been proved to be a rapid and specific tool to identify pathogenic Legionella spp. and L. penumophila viable cells harboured by FLA in these water sources, posing particular public health concern. [Display omitted] •Legionella is protected from harsh environmental conditions by FLA.•Viable Legionella was found inside FLA in wastewater and drinking water.•Potentially pathogenic Legionella were recovered from environmental water.•DVC-FISH is a useful technique to detect VBNC Legionella from FLA.•Pathogenic internalized Legionella pose a problem concern to Public Health.