Abstract
Legionella pneumophila is a ubiquitous microorganism widely distributed in aquatic environments and can cause Legionellosis in humans. A promising approach to detect viable cells in water samples involves the use of quantitative polymerase chain reaction (qPCR) in combination with photoactivatable DNA intercalator propidium monoazide (PMA). However, the PMA efficiency could be different depending on the experimental conditions used. The aim of this study was to compare two PMA exposure protocols: (A) directly on the membrane filter or (B) in liquid after filter washing. The overall PMA-induced qPCR means reductions in heat-killed L. pneumophila cells were 2.42 and 1.91 log units for exposure protocols A and B, respectively. A comparison between the results obtained reveals that filter exposure allows a higher PMA-qPCR signal reduction to be reached, mainly at low concentrations (p < 0.05). This confirms the potential use of this method to quantify L. pneumophila in water with low contamination.
Highlights
Legionella is a ubiquitous microorganism that is widely distributed in aquatic environments.From natural reservoirs, it can reach and colonize artificial aquatic environments such as the water system of buildings, cooling towers, evaporative condensers, and dental unit waterlines [1,2,3,4].Legionella pneumophila is the species most frequently found in human disease, causing Legionnaires’disease or the flu-like Pontiac fever in humans, through inhalation of contaminated water aerosols [5].Environmental monitoring represents an important tool for the assessment of Legionella contamination
Assessments of L. pneumophila in water are typically performed by culture isolation on selective media
Legionella culture growth is essential for identifying and typing Legionella strains, it has several limits including the long incubation times required for the growth of colonies, the simultaneous growth of other bacteria, and the inability to detect the viable but non-culturable bacteria (VBNC) that may represent a public health hazard [6]
Summary
Legionella is a ubiquitous microorganism that is widely distributed in aquatic environments.From natural reservoirs, it can reach and colonize artificial aquatic environments such as the water system of buildings, cooling towers, evaporative condensers, and dental unit waterlines [1,2,3,4].Legionella pneumophila is the species most frequently found in human disease, causing Legionnaires’disease or the flu-like Pontiac fever in humans, through inhalation of contaminated water aerosols [5].Environmental monitoring represents an important tool for the assessment of Legionella contamination. Legionella is a ubiquitous microorganism that is widely distributed in aquatic environments. From natural reservoirs, it can reach and colonize artificial aquatic environments such as the water system of buildings, cooling towers, evaporative condensers, and dental unit waterlines [1,2,3,4]. Quantitative polymerase chain reaction (qPCR) has been proposed as an alternative tool for rapid, sensitive, and specific detection of Legionella in water samples. This method may overcome many disadvantages of traditional culture methods; qPCR does not allow viable cells to be distinguished from
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