Analysis of water for Legionella bacteria

Legionella bacteria have been regarded as a human pathogen since 1977. In 1976, in the Bellevue-Stratford Hotel in Philadelphia, USA, a meeting of the American Legion veterans was held (hence the name Legionella). 221 participants fell ill and 34 died from a mysterious disease. Long-lasting tests and analyses showed that the disease had been caused by bacteria present in the hotel air-conditioning system. The disease is commonly referred to as legionellosis and it is caused by a strain of Legionella pneumophila.

Growth of the bacteria under natural conditions takes place in the presence of heterotrophic bacteria, actinobacteria, fungi, algae, and particularly protists from the groups of Ciliata and Amoeba. Legionelleae absorb substances which are necessary for their growth from live or dead cells of those organisms. Natural biotopes are the sources from which Legionelleae spread in the human work and living environments. The bacteria, together with the organisms on which they grow, flow with the surface water used in water treatment stations to hot and cold water distribution systems, water containers, sprinkling chambers of air-conditioning systems, medical devices (breathing supporting devices, water pipes of dental turbines, dialysis machines). Legionella bacteria are able to survive in a broad range of temperatures from 5 to 63°C and they grow within the temperature range from 20 to 50°C.


In the era of globalisation and technology development, you have to make journeys during which you make use of hotel chains. You also – increasingly often – stay in air-conditioned rooms. After work, you want to regenerate yourself and go to swimming pools, sauna, Jacuzzi.   Considering the permanent stress and deteriorating health, everyone is more and more susceptible to various infections, including those caused by Legionella bacteria.

Due to common occurrence of Legionella in water systems, it is very important that such systems should be constantly and strictly monitored. Regardless of the type of a water distribution system, the appropriate technical solutions have to be chosen, the factors which boost Legionella growth should be controlled and the system should be cleaned and disinfected regularly.  

The obligation to test water for Legionella in utility buildings has been introduced in many European countries. Frequency of sampling and size of samples depends on the results and place of sampling.

Pursuant to the Regulation of Minister of Health of 29 March 2007 on the quality of water intended for human consumption (J. of Laws No. 61, item 417), microbiological requirements that should be met by hot water have been in force since 1 January 2008. Appendix 1 point D specifies the microbiological requirements that hot water should meet. The point concerns the presence of Legionella bacilli. The highest permissible level is <100 cfu in 100 mL of water.


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