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Legionellosis is a bacterial infection caused by the agent Legionella pneumophila , originally identified in 1977 when it caused the death of 34 people due to an outbreak of pneumonia. It was for this reason that they called it the “disease of the legionaries”. Currently there are two clinical and epidemiological forms caused by this bacterium.

The first was the disease of the legionaries, this being the pneumonic form. Second, there is the non-pneumonic form described as “Pontiac fever”. Likewise, about 42 species and 64 serotypes of this bacterium have been studied. Serotype 1 is responsible for 90% of the cases of legionellosis.


Legionellosis is a bacterium housed especially in areas of America, both in the northern region and in the south. They have also isolated themselves in Australia, Africa and also Europe.

This bacterium usually adheres especially to natural water sources such as lakes, streams, rivers and hot springs since it has very diverse living conditions in various types of environments. Its amount to be pathological in the

The incidence of nosocomial pneumonia caused by Legionella pneumofila depends on the degree of colonization of water distribution systems of hospital origin

The bacteria will also have dependence on hosts that are susceptible to being a bacterium receptor. Therefore, those patients who are severely immunocompromised will be at greater risk and also:

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In its entirety, the route of transmission of Legionella is aerial, through droplets of saliva that can be expelled involuntarily when talking, sneezing and even laughing. Another form of transmission is through aerosols, which expel drops that can be easily inhaled.

The bacteria enters the lungs through inhalation and affects the alveoli, releases No evidence of contagion has been described by contact from person to person.

However, it has been shown that this bacterium has a predilection for people with susceptible age (such as the elderly) who have comorbidities such as alcoholism, smoking or are immunocompromised. This does not mean that healthy people are not exempt from infection.

When should one suspect legionellosis?

In those cases of

Many cases of Legionella infection are directly associated with ventilatory breathing equipment. For this reason you should explore if there has been direct contact with this type of assisted breathing systems or not



Lung form

  • Cough with mucopurulent sputum.
  • Pleuritic chest pain.
  • Thermal boosts of 39 ° C.
  • Hemoptysis.
  • Dyspnoea.

Extrapulmonary form

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The definitive diagnosis will depend on the isolation of the microorganism in direct immunofluorescence media by staining the tissue plus detection of antigens of the Legionella serotype 1 bacteria in urine.

The culture medium is also used by a polymerase chain reaction that shows the level of reproduction that it has had since the infection. If necessary, sputum culture is requested , which will determine with good precision if it is this nosocomial bacterium or not.

Treatment of Legionellosis




It has broad antibiotic properties that constitute the mother treatment that has been used since the discovery of the disease of the legionaries. The mother drug of the macrolides is erythromycin , which requires progressively large volumes of perfusion and is applied intravenously.

The following are also recommended for the macrolide line, such as azithromycin, roxithromycin and josamycin, which are really effective and are intended for oral administration.


It is preferred in forms that manifest as severe infections. Levofloxacin and ofloxacin are the active ingredients recommended as a complete treatment that covers the clinic left by the bacteria. However, its use must be limited due to the resistance that quinolones have had over the years.


Antibiotic treatment of legionellosis in adults.