Legionella

Legionella exist further in drinking water installations.

They are on of the most important waterborne pathogens. Even today the importance of hygiene in the technical areas remains often unrecognized. In the most cases facts geared towards the media create the awareness, that something „is wrong“. These facts are often discussed, but rarely assessed in terms of responsibility, and regularly forgotten again.

Below a short part of our presentation „Answers to the most common questions around Legionella“

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What are Legionella?

Legionella are waterborne aerobic gram-negative, rod-shaped no spore-forming bacteria with a size of 0.3 – 0.9 µm in diameter and 2 – 20 µm in length. They are mobile through several polar and subpolar flagella.
Their name has been given during an outbreak in Philadelphia / US in 1976 caused by a contaminated air washer system of the air conditioning in a hotel. 221 out of 4400 participants in a veteran meeting had contracted pneumonia and 34 people died.
In 1977, CDC (Center for Disease Control) researchers in Atlanta/US identified rod-shaped bacteria as the outbreak cause, and named them „Legionella“.
Legionella multiply every 3 – 4 hours under normal conditions. Over 65 Legionella species with different serogroups have been identified by now, some of which are pathogenic for humans. Within one serogroup further subtypes can occur. The most well-known and best described species are Legionella pneumophila with 16 serogroups. Legionella pneumophila Serogroup 1 has caused the most infections described in the literature.
Legionella are pathogens according to German Infection Protection Law and categorized as one of the most important waterborne pathogen in Germany by the Robert Koch-Institute, Berlin.

How can Legionella be described?
– gram-negative bacteria (rod-shaped)
– they are not spore-forming
– aerobe
– not all species are pathogenic for humans
– mobile through several polar and subpolar flagella
– Size:
– 0.3 – 0.9 µm in diameter
– 2 – 20 µm in length

Where can Legionella occur?

Legionella can occur in water, waste water and soil. Cold and hot water systems usually provide ideal growth conditions for Legionella including low flow rates and/or stagnation, temperatures between 25 and 45 °C and high nutrient concentrations (2).

Following buildings can commonly be contaminated with Legionella:
– healthcare buildings including hospitals, elderly homes, rehabilitation centres
– Non-healthcare buildings including hotels, apartment buildings, schools, university halls, kindergardens, sport centres, spas, industrial buildings and public buildings including prisons

Following water systems can commonly be contaminated with Legionella:
– hot and cold water systems
– cooling towers
– air washers (air conditioning)
– Swimming pools
– whirlpools and jacuzzis
– dental units
– Car washing systems
– Water fountains and other decorative water systems

Number of Legionella pro volume unit is defined through the biological balance.

How can Legionella cause infections?
Legionella can cause 2 different infections in humans: the Pontiac fever, an infection with common flu-like symptoms, and a Legionnaires‘ Disease, which is a severe form of pneumonia. There are only few Pontiac fever cases described, as most flu-like cases are not diagnosed or reported. Legionella particles can be inhaled through contaminated droplets and aerosols, or be aspired and end in the lungs, thus causing an infection. Similar to other microorganisms, there is no proven dose – effect relationship for Legionella: whether a human contracts Legionnaires‘ Disease depends on many different factors including age, sex, immune status, Legionella species and serogroups, bacterium virulence and others.

Legionella

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