The gram negative, non-spore-forming aerobic bacterium Legionella (L.) pneumophila is one of about 57 species of the family Legionellaceae, which are comprised of 79 serogroups. Legionella live exclusively in humid environments or waters and move through them with the help of a scourge. All Legionella species are classified as human pathogens, with L. pneumophila being known as the most aggressive infectious agent. This species is responsible for 90 percent of Legionella diseases. Infections with Legionella occur sporadically and in outbreaks worldwide. The origin of such cases is often hot water tanks, heating systems or air conditioning systems.
Infections occur exclusively through sources in the environment, as Legionella are common and naturally occurring germs. They are constantly present in small numbers, especially in groundwater, where they multiply at temperatures around 55 degrees Celsius in protozoa such as amoebae. When legionella is washed into groundwater-fed pipe systems or warm water systems, it settles on biofilm and deposits. Standing tap water is also a breeding ground.
Drinking contaminated water is not dangerous. Only contaminated water vapor, which reaches the lungs while showering or in air-conditioned rooms, can cause pneumonia.
An infection caused by the bacterium L. pneumophila can cause Legionnaire’s disease and Pontiac fever as well as be asymptomatic. In Legionnaire’s disease, the first symptoms appear after an incubation period of about six to seven days. They manifest themselves in the form of severe atypical pneumonia, combined with discomfort, pain in the limbs, headaches and an unexplainable dry cough. In addition, chills and thoracic pain set in after a short time, accompanied by an increased body temperature of up to 40.5 degrees Celsius (104.9 degrees Fahrenheit) and diarrhea. In ten to 15 percent of cases, Legionnaire’s disease leads to death.
Pontiac fever, on the other hand, is a legionellosis without pneumonia that breaks out after 24 to 48 hours of incubation. The characteristic feature is the much easier course of the disease compared to Legionnaire’s disease. The symptoms consist of flu-like signs such as headache, pain in the limbs and thorax, dry cough, fever and short-term confusion. Worldwide, no deaths have been recorded from Pontiac disease thus far.
Basic hygiene measures are considered to be sufficient, as a person-to-person transmission is generally not to be feared. Direct and indirect detection as well as an infection with Legionella spp. must be reported to health authorities.
The required spectrum of action against Legionella pneumophila is: bactericidal.