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General Introduction

Legionellosis is the collective name given to the pneumonia-like illness caused by Legionella bacteria. This includes the most serious Legionnaires’ disease caused by Legionella pneumophila, as well as the similar but less serious conditions of Pontiac fever and Lochgoilhead fever. Humans are accidental hosts of the Legionella bacteria and infection occurs as a result of breathing in contaminated water droplets in the form of aerosols.  The bacteria enter the lungs where conditions are favourable for growth.  Particularly vulnerable are the elderly, the immunosuppressed and smokers.

Where can Legionella be found?

There are over 40 species of Legionella bacteria, and they survive under a wide variety of harsh conditions. Like many organisms, they experience rapid growth in water temperatures between 20-45°C and can survive in temperatures of up to 60˚ C.

The following water sources provide optimum conditions for the growth of Legionella:

  • Cooling towers, evaporative condensers and fluid coolers
  • Domestic hot-water systems with water heaters that operate below 60˚C
  • Equipment that creates a water spray and use water at temperatures favourable to growth of the organism
  • Spas and whirlpools
  • Dental water lines
  • Other sources including stagnant water in fire sprinkler systems and warm water for eye washes and safety showers

Regulatory Information

To safely manage water quality, it is vital that water systems are properly assessed for the risk of hosting, and routinely tested for the presence of Legionella bacterium.  The Approved Code of Practice, The Control of Legionella Bacteria in Water Systems (ACOP L8) published by the HSE, details the requirements for regular monitoring and measuring that is required to take place to demonstrate the control of Legionella.


20/30 Labs Limited are registered with the Legionella Control Association for Analytical Services and are a UKAS accredited laboratory (4236) for the detection and enumeration of Legionella in rinse, reverse osmosis, potable, spa, swimming pool and hydrotherapy pool waters.

Analytical Methods

20/30 Labs are a UKAS accredited laboratory (4236) for the detection and enumeration of Legionella according to; ISO 11731 Part 2, for the direct plate method and ISO 17731 Part 4, for the three plate method. ISO 17731 is used for the analysis of process or waste waters.

The presence of Legionella bacteria is analysed by filtering samples onto GVPC agar, a Buffered Charcoal Yeast Extract (BCYE) agar containing the selective agents glycine, vancomycin, polymixin and cyclohexamide (GVPC), and incubating samples at 36°C ± 2°C for a period of at least 10 days.  Plates are examined for any growth on three occasions; at Day 4, Day 7 and Day 10.  Presumptive colonies are confirmed by their ability to grow on BCYE agar but an inability to grow on non-selective TSA (due to an absence of L-cysteine).  Confirmed Legionella can be further characterised using an antibody latex agglutination test to characterise the isolate as Legionella pnuemophila (Serogroups 1 or 2-14), or Legionella species.

Hospital Analysis

A vast suite of standard and specialist analyses are available. Read More

Potable Water Testing

A range of tests available as required by the MODW and HTM 04-01. Read More

Pseudomonas Aeruginosa

The detection and enumeration of Pseudomonas aeruginosa according to HTM 04-01 and the MODW. Read More

Legionella Testing

Accredited to ISO 11731-2:2008 to carry out detection and enumeration of Legionella. Read More

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