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

Area of Science:

• Environmental microbiology
• Water quality analysis
• Public health microbiology

Background:

• Legionella and free-living amoebae (FLA) can survive disinfection treatments in water.
• FLA can harbor and protect pathogenic Legionella, enhancing their infectivity.
• Assessing the risk of Legionella within FLA in water sources is crucial.

Purpose of the Study:

• To rapidly and specifically identify viable Legionella spp. and Legionella pneumophila within FLA in water samples.
• To evaluate the prevalence of Legionella internalized in FLA in drinking and wastewater.
• To assess the public health implications of FLA harboring Legionella.

Main Methods:

• Processing of 55 water samples (30 wastewater, 25 drinking water).
• Detection of FLA using microscopy and culture.
• Identification of viable, internalized Legionella spp. and L. pneumophila within FLA using dual-channel in situ hybridization (DVC-FISH).

Main Results:

• FLA were detected in 52.7% of water samples.
• Viable Legionella spp. were found inside FLA in 69.0% of FLA-positive samples (70% wastewater, 66.7% drinking water).
• L. pneumophila was identified in 48.3% of FLA-positive samples (50% wastewater, 44.4% drinking water).
• Potentially pathogenic Legionella were cultured from 27.6% of FLA-positive samples.

Conclusions:

• FLA can facilitate the survival of Legionella bacteria against disinfection processes in both drinking and wastewater.
• FLA act as significant vectors for pathogenic Legionella, posing a public health concern.
• DVC-FISH is a rapid and specific method for detecting viable Legionella within FLA in water systems.