Legionella

Human-pathogenic species of the genus Legionella are globally distributed environmental germs that cause various disease patterns in humans, ranging from flu-like symptoms to severe pneumonia. Legionella are in small numbers natural components of surface and ground water. Human pathogens are mainly L. pneumoniae (15 serogroups), L. micdadei and L. bozemanii. There are a further 48 species and 70 serogroups that have only led to the disease in patients with significant immune deficiencies.

Legionella proliferate best at temperatures between 25 °C and 45 °C. Above 60 °C they are usually killed off and below 20 °C they hardly multiply at all. Especially in artificial water systems such as water pipes in buildings the pathogens find good growth conditions at appropriate temperatures. Legionella can multiply particularly well in deposits and deposits in the pipe system.

Transmission: The pathogens are transmitted by atomized, nebulized water. The pathogen-containing droplets can spread in the air and be inhaled. Possible sources of infection are, for example, showers, whirlpools, humidifiers or water taps, as well as cooling towers, etc. When drinking, infection is only possible if water is accidentally aspirated when swallowed.

Important: Legionella is not transmitted from person to person.

Epidemic: m>w; children rarely fall ill.

Legionella cause 2 clinical pictures in humans:

• Legionnaires'disease / Legionella pneumonia: Legionnaires' disease, or Legionella pneumonia, is an atypical pneumonia. It affects mainly elderly and immunocompromised patients. After an ICZ of 2-10 days, cough, chills, headache, varying degrees of illness and high fever occur. Diarrhoea occurs in about 50% of patients. Subsequent respiratory symptoms: pneumonia and pleurisy. Often as a nosocomial infection!
• Pontiac fever: In immunocompetent patients, it manifests itself in flu-like symptoms such as fever, malaise, headache and pain in the limbs, but not in pneumonia. Frequent epidemic occurrence. The disease resolves spontaneously within a week.
• Pittsburg pneumonia: Legionella infection in immunocompetent individuals. Severe Legionella pneumonia. The causative agent is Legionella micdadei.

Detection methods:

• Culture: tracheal secretion, BAL, pleural puncture and biopsy material.
• Urine for AG detection. Within the framework of hospital hygiene measures, taking water samples from air conditioning and cooling systems.
• Serology: 1-2 ml serum. AK but only detectable from the 2nd week of illness. No serum conversion in some patients.

The drug of choice is azithromycin or other modern macrolide antibiotics. For severe disease and immunosuppression in combination with rifampicin. Alternative: Quinolone antibiotics like Ciprofloxacin (2-3x400mg i.v. as short infusion or 2x250-750mg p.o./day) or Moxifloxacin (1x400mg/day p.o. or i.v.)

It is important to avoid the proliferation of legionella in the pipe system of the drinking water installation. Special technical regulations apply to the construction and maintenance of drinking water installations. According to the Drinking Water Ordinance, water samples are regularly taken from large plants and public buildings as well as from plants for commercial purposes. If a certain concentration of Legionella is detected, this must be reported to the public health department. The following safety measures can help to prevent a massive increase of legionella in the hot water system of a residential building:

Basically, the water pipes should be used regularly.

Dead lines in the pipe system should be avoided (avoidance of water stagnation in the pipes).

In a house with central water heating and central hot water storage, the controller temperature should be set to > 60 °C.

The water temperatures should not be lower than 55 °C at any point in the pipe system.

1. Neumeister B (2018) Bacterial infections. In: Neumeister B et al. (Eds) Clinical guide to laboratory diagnostics. Elsevier GmbH S. 605-606