Diagnosis: Legionella in drinking water


Legionella in drinking water? - New diagnostic procedure developed Germs in drinking water are always a problem. Despite strict controls and extensive hygiene measures, contamination occurs again and again. So-called legionella bacteria can also be transmitted, which cause severe pneumonia and were previously difficult to detect in drinking water. However, researchers at the Braunschweig Helmholtz Center for Infection Research (HZI) have now developed a very precise and fast diagnostic procedure at the molecular level that greatly improves the diagnosis and the cause research for Legionella infections.

Heaters, showers, air conditioning systems - Legionella are widespread Legionella can be found relatively often in hot water production and distribution systems, swimming pools, air conditioning, showers, water tanks, but also cold water pipes with external heat. Water temperatures of 25 to 59 degrees Celsius, with a long dwell time and simultaneous fresh water supply form the optimal living conditions for Legionella. Aerosols, the finest droplets in the air, take the rod-shaped bacteria deep into the respiratory tract, where they can trigger Legionnaires' disease with the appropriate pneumonia. Although all Legionella are potentially pathogenic to humans (transmissible to humans), only the Legionella pneumophila pathogen has so far been the cause of Legionnaires' disease for humans. However, since the bacteria were difficult to isolate and cultivate, it has been extremely difficult to detect the different types of pathogens.

New diagnostic procedure improves detection options To remedy this situation, researchers at the Braunschweig Helmholtz Center for Infection Research (HZI) have now developed a new diagnostic procedure at the molecular level, which they published in the current issue of the specialist journal "Applied and Environmental Microbiology" On the one hand, any legionella can be found in the drinking water, on the other hand, it can easily be determined whether they belong to a strain that is dangerous for humans Could not determine origin exactly, "explained Manfred Höfle, researcher at the HZI. Höfle added: “Legionella pneumophila alone has 14 subgroups, so-called serotypes. The distinction between these different serotypes is very complex because legionella is difficult to isolate: they grow very slowly or are overgrown by competing bacteria. "

Detection based on repeating DNA sections In the new diagnostic procedure, the pathogens are therefore detected via the characteristic sections of their DNA, explained Manfred Höfle. For the first time, his team of researchers has succeeded in adapting the known methods for obtaining and reproducing Legionella DNA so that the individual bacterial strains can be detected directly from a water sample, according to the HZI specialist. Höfle explained that “in the past (...) the concentration and purification of DNA from drinking water was problematic. In addition, the necessary degree of genetic resolution has not yet been reached. "However, together with his research colleague, who had a lot of experience in the analysis of water samples and the detection of germs contained in them, the difficulties were overcome by improved methods." We can now shorten the time "Detect repeating DNA sections, so-called tandem repeats, in the legionella genome," explained Höfle, the tandem sections being marked in color and providing comparable patterns for the different bacterial strains. "We can use this to check not only which germ the water sample contains, but also how pathogenic it is to humans," continues the expert. Manfred Höfle believes that the new diagnostic method could make a significant contribution to the risk management of drinking water systems in the future Not only can the general quality be better checked, but the method also helps to detect biofilms (deposits of microorganisms on the water surface or at contact points with solid objects) that favor the occurrence of Legionella.

Diseases caused by Legionella, also common in Germany, were first identified in 1976 at a veteran meeting of the "American Legion" at the Bellevue-Standfort Hotel in Philadelphia. Out of 4,400 delegates, 180 and 29 fell ill with severe lung infections. By the time the health authorities developed the character of an epidemic, legionnaires' disease was in full swing. The bacterium was only detected in the lung tissue of a deceased veteran in early 1977. Since then, legionella has been detected worldwide and there are also occasional infections in Germany. An outbreak of legionnaire's disease with epidemic character is relatively rare in Germany. However, such an incident occurred in the Ulm area in early January 2010. According to official information, 64 people fell ill with Legionnaires' disease and five people died as a result. The cooling towers of a combined heat and power plant near the Ulm main station are primarily suspected as the source of the infection. The Dresden University of Technology is currently investigating the risk posed by the cooling towers. (fp, 14.10.2010)

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