Legionella Sampling & Analysis
Legionella is a risk for almost all water found within your building, as your water systems can create the perfect environment for the many microbes to contaminate and thrive in the system.
The simplest way to understand if you have Legionella under control is to test for it in your water system.
Legionella is a pathogenic gram-negative bacterium, including the species that cause legionellosis (Legionnaires' disease), most notably Legionella pneumophila.
Legionella is common in many environments, with at least 50 species and 70 serogroups identified.
In the UK, it results in around 400 identified cases a year, though actual case numbers are probably nearer to 5,000–6,000 per year (HPA 2012). It can prove fatal, especially to the elderly or those prone to respiratory problems. Legionnaires’ disease is contracted by inhaling small droplets of water suspended in air that contain the Legionella bacterium.
In the Laboratory
The incubation time for Legionella in the laboratory is 10 days, and a further 2 days may be required if the sample is positive.
It is traditionally detected by the culture method on an agar plate, which is still considered the ‘Gold Standard’. Results are provided in CFU (Colony Forming Units), which have specific useful guidance for how to react to levels detected in the HSE’s ACoP L8 document.
The Rationale for Sampling
The rationale for any sampling programme is to test if the control measures you have in place for Legionella are suitable and sufficient or not. Therefore the simplest way to is to test for it in your water system.
The responsibility to test your control scheme is described under COSHH Regulation 9, and associated guidance ACoP L8, along with specific British Standards, but should be informed in conjunction with the advice of the risk assessment or the policy of the specific authority so that the sampling programme is specific and proportionate to the building.