Evaluation of Legionella qPCR against traditional culture for routine and public health testing of water samples.

Legionella is a pathogenic, gram-negative bacteria responsible for causing Legionnaires’ disease, a potentially fatal form of pneumonia, for which there is currently no vaccine. The bacteria are found in water supplies, making the maintenance of water systems essential in preventing the disease.

Traditionally water systems are tested for the presence of Legionella using a culture method. The bacteria are only able to grow in the presence of cysteine, therefore colonies can be confirmed as Legionella if they are able to grow on buffered charcoal yeast extract agar but not on blood agar media (which lacks cysteine). This culture method requires an incubation period that typically lasts about 10 days, enabling the bacteria to spread further by the time their presence is realised.

This investigation found that using Legionella qPCR reduced the time to results significantly. The method described utilises the high negative predictive value of qPCR to rule out uncontaminated samples. No cell culture is needed, enabling a more rapid, efficient response. qPCR has been proposed as a valuable tool for routine and public health testing of water supplies.

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