Legionella pneumophilia and Legionnaires’ Disease in Water Systems and Biofilm

Legionella bacteria are the microorganisms which can cause serious infections in people. They cause infections having the two types, namely Legionnaires’ Disease and Pontiac fever. Legionnaires’ Disease is an infection which is dangerous and which is a type of pneumonia (lung infection). Pontiac, on the other hand, is a mild form of the respiratory diseases.

Legionella bacteria are formed by itself in the environment. Artificial water systems can form favorable environments for the Legionella bacteria to reproduce in high numbers. The examples of the aforementioned systems can be evaporative coolers, condensers, and cooling towers. It is important to know and remember that the cooling towers are highly effective air handler. Cooling tower takes the all airflow passing and drifting around the tower inside and incorporates into the system.

Legionnaires’ Disease was firstly described after a pneumonia epidemic broke out among the participants staying in the hotel in a legionnaire congress in Philadelphia, America in 1976. In this epidemic, in which 221 people were affected in total, 34 people died. It was detected that the factor of the epidemic is a new gram negative (-) bacteria which was not identified until that day and it was named as Legionella pneumophila based on the name of the congress.

The distinct clinical feature of Legionnaires’ Disease is pneumonia. After 2-10 days of exposure to the factor, clinical picture is seen. High fever (>38,50°C), headache and myalgia are among the first signs. Then, chest pain might accompany with the developed pneumonia and pleurisy. Symptoms such as gastroenteritis and vomiting in 1/3 of the cases, mental and neurological symptoms in 50% of the cases are seen. Patients generally apply to the hospital in 3-6 days and it can result with death in 15-20% of the patients.

Where Legionella pneumophila can reproduce easily?

* Hotels *Residences *Hospitals *Schools *Hot springs *Thermal and ornamental pools *Shopping malls *Thermal Baths
* Thermal Muds * Streams, small lakes and soil in their coasts *Aerosol coming from the excavated soil


Biofilm is the colony which microorganisms, living in a jelly layer that they produce themselves by adhering to live or abiotic surface, form. Legionella type bacteria are protected from the fluctuations of disinfectants, biocides, temperature and pH in this layer.

Biofilm layer can form in the cracked and corroded surfaces due to suture and corrosion, in the dead regions where the water circulation do not reach, in the connection systems of the pipes and in the sand filters.

1-Bacteria approaches to the surface they will attach with an active movement or a convection movement.
2-They adhere to the surface where they will attach with the effect of repellent and attractive forces.
3-Bacteria strictly attached to the surface form the biofilm layer.
4-After the formation of biofilm, a thin layer is split off the biofilm and passes to the water. So, microorganisms in the biofilm can pass to the system water and can reach to the other parts of the system and colonize in the suitable parts.
The Critical Points Suggested for the Sample Taking for Legionella pneumophila in the facilities
Sample taking and analysis periods in the critical control points were determined as once in a month by World Health Organization (WHO).
1-All the Hot Water Tanks (it should be tested with duplicate sample)
2-All the Cold Water Tanks (including the softening tanks, they should be tested with duplicate sample)
3-Air-conditioning system cooling tower (it should be tested with at least one sample)
4-Air conditioning system condenser (it should be tested with at least one sample)
5-Shower heads of at least one room in all floors (it should be tested with at least one sample)
6-The lavatory faucets of at least one room in all floors (it should be tested with at least one sample)
7-Turkish bath, if available (it should be tested with a few sample)
8-Water of thermal pools, if available (it should be tested with a few sample)
9-Artesian well or the depot of the artesian water, if available (it should be tested one sample for each)
10-Decorative/fountain pool of the building lobby (it should be tested with at least one sample)
11-Respiratpory therapy equipments in the hospitals (it should be tested with at least one sample)