The Royal (Dick) School of Veterinary Studies

Genetic analysis key to understanding Legionella risk

Regular analysis of the bacteria that causes Legionnaires' disease could help measures to limit the spread of infection.

Routine sampling of water supplies and genomic sequencing of Legionella bacteria – determining its entire genetic makeup - could play a key role in identifying the source of Legionnaires’ disease outbreaks, research suggests.

The measures could also inform public health efforts to limit the spread of infection, according to a genomic study of the Legionella bacteria that causes the disease.

Improved testing is crucial, researchers say, because the disease – a severe form of pneumonia – is contracted by inhaling the bacteria in aerosols – tiny droplets - of contaminated water.

Outbreaks are often linked to water systems in hotels, cruise ships and hospitals, and also within the community.

Tracing transmission

A team from the Roslin Institute and the University of Glasgow, Public Health Scotland and the Scottish Legionella Reference Laboratory compared the genomes, or genetic codes, of more than 3,000 Legionella bacteria samples found in patients and in water sources from Scotland and around the world.

The results revealed a new level of detail and fresh insights into the characteristics of Legionella bacteria and its transmission in Scotland.

From analysis of the genetic code, researchers found that Legionella infections linked to people travelling were often closely related to other variants from the same UK or international destination.

The analysis found that nearly one-third of infections in Scotland acquired in the community - not hospital or travel associated - were caused by a single variant. The team say this variant should be closely monitored.

Distinct variants of the bacteria were found in some hospitals over a long period of time – up to 17 years in some instances - which suggests that the bacteria persisted or were repeatedly introduced into hospital water systems.

The team also found that there had been no reported cases of Legionnaires’ disease in any Scottish hospital in the past 10 years. This is likely due to effectiveness of new control measures introduced during this time, experts say.

The findings have been published in The Lancet Microbe.

This work has been funded by the Chief Scientist Office, UKRI and Wellcome.

Our study indicates that regular sampling of water systems and genome sequencing of Legionella could be used to identify the source of new pathogenic variants before they become a clinical problem.

Professor Ross Fitzgerald Roslin Institute

** The Roslin Institute receives strategic investment funding from the Biotechnology and Biological Sciences Research Council and it is part of the University of Edinburgh’s Royal (Dick) School of Veterinary Studies. **

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About the Royal (Dick) School of Veterinary Studies

The Royal (Dick) School of Veterinary Studies is a one-of-a-kind centre of excellence in clinical activity, teaching and research. Our purpose-built campus, set against the backdrop of the beautiful Pentland Hills Regional Park, is home to more than eight hundred staff and almost fourteen hundred students, all of whom contribute to our exceptional community ethos.    

The School comprises:   

  The Roslin Institute   

The Global Academy of Agriculture and Food Systems   

The Roslin Innovation Centre   

The Hospital for Small Animals   

Equine Veterinary Services   

Farm Animal Services   

Easter Bush Pathology   

The Jeanne Marchig International Centre for Animal Welfare Education   

We represent the largest concentration of animal science-related expertise in Europe, impacting local, regional, national and international communities in terms of economic growth, the provision of clinical services and the advancement of scientific knowledge.