Legionellosis

legionellosis, legionnaires' disease or legionella is an infectious disease caused by an aerobic Gram-negative bacterium of the genus Legionella.

The infection can manifest itself in two different ways:

• the Pontiac fever, which is the mildest form of infection and attends benevolously,
• the Legionnaire disease, name of the disease and more severe form of infection, which has atypical pneumonia and very high fever.

90% of legionellosis cases are caused by Legionella pneumophila, a ubiquitous aquatic organism that thrives at temperatures between 25 °C (77.0 °F) and 45 °C (113 °C). F), and an optimum of 35 °C (95.0 °F).

Legionellosis epidemics tend to be the focus of media attention due to their frequent association with specific facilities. However, this disease usually appears as an isolated case, not associated with any officially recognized outbreak. The epidemic usually appears in the summer or early fall, but cases can occur throughout the year.

Some infected people may have mild symptoms or no symptoms at all. About 5% to 30% of people with legionellosis die, especially if antibiotic treatments have been delayed. It is estimated that 8,000 to 18,000 people suffer from legionellosis in the US each year.^{[citation required]}

History

Legionnaires' disease or legionellosis acquired its name in 1976, when an outbreak of pneumonia appeared among attendees at the 58th American Legion convention in Philadelphia (USA).

On January 18, 1977, scientists identified a previously unknown bacterium as the cause of the mysterious Legionnaires' disease infection. It was a bacterium of the genus Legionella, of which Legionella pneumophila stands out.

Epidemiology

Legionella is frequently found in natural water bodies, however it is urban water systems that represent the main source of disease for humans. Legionella breeds in biofilms within water systems and is relatively resistant to chlorine levels in drinking water. Developments of aerosol storage and generation systems such as cooling towers, spas, outdoor and indoor water fountains, showers, and atomizers in grocery stores have increased its transmission.

People of any age can develop legionellosis, but the disease most frequently affects men over 45, smokers, and immunosuppressed (whether due to diseases such as cancer, diabetes, or AIDS; on dialysis or who take medicines that suppress the immune system.

Outbreaks of legionellosis occur when people have inhaled aerosols containing water (for example, from cooling water towers for air conditioning, fountains, irrigation sprinklers, showers) contaminated with legionella bacteria. People can be exposed to these aerosols at home, workplaces, hospitals, and public places. Legionnaires' disease is not transmitted from person to person and there is no evidence of infection with the disease in car air conditioners or home air conditioning units.

The largest outbreak of legionellosis in history took place in July 2001 in Murcia, Spain, with 6 deaths and more than 600 affected. The focus was located in several ventilation towers: in El Corte Inglés, in the Departments of Health and Agriculture, in the San Esteban Palace and in the central headquarters of Caja Murcia.

Another outbreak took place during the autumn of 2014 in Catalonia, Spain, with 10 deaths (six in Sabadell and four in Ripollet) and more than forty infected, four of them hospitalized and one very serious. The focus of this outbreak has not been clarified.

Another outbreak emerged in May 2018 in the city of Úbeda, Jaén, Andalusia with 4 people admitted to the ICU, for now unresolved.

The most recent outbreak to date is in the Province of Tucumán, Argentine Republic, with 5 deaths. The focus was on Luz Medica, a private clinic. Until September 4, 2022, there is a lack of confirmatory evidence that it is really Legionella and what species it would be, only preliminary metagenomic data is available on samples from 3 patients

Etiology

Legionellosis is caused by bacteria of the Legionellaceae family, which consists of more than 42 species. L. pneumophila is the most common species, causing 90% of legionellosis. The rest is produced by L. micdadei, L. bozemanii, L. dumoffii and L. longbeachae.

Clinical picture

Patients with legionellosis typically have fever, chills, and a cough, which may be dry or with mucus. Some patients also have muscle pain, headache, tiredness, loss of appetite, and occasionally diarrhea. Laboratory tests indicate that the kidneys of these patients are not working properly. Chest x-ray frequently shows pneumonia. It is difficult to distinguish Legionnaires' disease from other types of pneumonia simply by symptoms; Other tests are needed to establish its diagnosis.

Recent studies show cell death in rat macrophages through activation of cytosolic Naip5 (Birc1e) receptors. People with Pontiac fever have fever and muscle aches and do not have pneumonia. They take to recover from 2 to 5 days without treatment.

The time between the patient's exposure to the bacteria and the onset of Legionnaires' disease is 2 to 5 days; for Pontiac fever, the time frame is shorter, usually from hours to 2 days. Onset or recovery is variable.

Micrograph with sample details of lung tissue of a patient with fatal pneumonia, due to legionary disease. Tejido dyed with hematoxylin-eosin staining, where those organisms, if present in the sample, are stained with rose or red. Watch the alveolar spaces very congested and a leukocyte infiltrate in response to the infection

Diagnosis

Despite its easy growth in water systems, it is quite difficult to grow in vitro. As a consequence, most diagnoses rely on serologic techniques to detect increased antibodies. The diagnosis of legionellosis requires a special test that is not routinely performed on people who have a fever or pneumonia. Therefore, the physician should consider the possibility of legionellosis in order to obtain the appropriate tests. Sputum, pleural fluid, bronchial washings, and lung biopsies or aspirates can be examined by immunofluorescence and with a spirochete modification of Dieterle.

There are several types of tests. The most useful detect the bacteria in mucus, find Legionella antigens in urine, or compare Legionella antibody levels in two blood samples taken 3 to 6 weeks apart.

Treatment

Erythromycin and levofloxacin are the antibiotics currently recommended to treat people with Legionnaires' disease. In the most severe cases, rifampicin can be used as a second medication. Other medicinal substances are available for patients who do not tolerate erythromycin. Pontiac disease does not require specific treatment.

Prevention

The fundamentals of legionellosis prevention are the improved design and maintenance of cooling towers and water conveyance systems —especially sanitary hot water—, to limit the growth and spread of legionella microorganisms.

During epidemics, researchers from health departments try to identify the source of the disease, make appropriate prevention recommendations, and take control measures, such as decontamination of the water source. Current research will offer additional prevention strategies in the future.

Legionella is very vulnerable to high doses of chlorine. The iron support influences its growth, which is why it is achieved through the iron of the water pipes and it is very dangerous in the shower heads, so it is better that they be made of plastic.

• 70 - 80 °C (158 - 176 °F): range of disinfection
• At 66 °C (150.8 °F): Legionellae dies in 2 min
• At 60 °C (140 °F): they die within 32 min
• At 55 °C (131 °F): they die within 5 to 6 h
• Above 50 °C (122 °F): they can survive but do not multiply
• 35 - 46 °C (95 to 115 °F): ideal growth range
• 20 - 50 °C (68 to 122 °F): growth range
• Under 20 °C (68.0 °F): they can survive but are latent

Action Levels

The European Working Group on Legionella Infections (EWGLI) was established in 1986 within the framework of the European Union to share knowledge and experience on possible sources of Legionella and its control. This group has published guidelines on actions that should be taken to limit the number of colony-forming units (i.e., the "aerobic count") of microorganisms per mL at 30 °C (minimum 48 h of incubation):

Nearly all natural water sources contain Legionella and their presence should not be taken as an indication of a problem. Figures presented are total aerobic count, rca/mL at 30 °C (minimum 48 h incubation) with colony count determined by the pour plate method according to ISO 6222(21) or in Petri dish and extract of yeast agar. Isolation of Legionella can be performed using the method developed by the United States Center for Disease Control using yeast extract buffered carbon agar with antibiotics.

Many other government agencies, cooling tower manufacturers, and industrial trade organizations have developed design and maintenance guidelines to prevent or control the growth of Legionella in cooling towers. However, in the United States there are no regulations that require testing or maintaining any specified level at these facilities.