Pneumonia caused by legionella: causes, symptoms, diagnosis, treatment

Currently, more than 30 species of legionella are described, 19 of them cause the development of pneumonia in humans. The most common is Legionella pneumophila. Legionella pneumophila was first isolated in 1977. The name was given to this microorganism by the name of the American Legion, among participants of the conference, an epidemic of pneumonia broke out.

Legionella are gram-negative bacteria, they are not part of the physiological flora of humans, are widely distributed in the aquatic environment, live in air conditioning, ventilation systems, in sanitary ware of showers, baths, water heaters, in lakes, rivers, streams. The main sources of outbreaks are aerosols containing legionella, from air conditioning systems, as well as in bathrooms, shower units. There are indications that legionella can be contained in drinking water flowing through infected faucets, as well as in the sewage system. They are also found in artificial thermal reservoirs, irrigation facilities.

Legionella pneumophila enters the lungs by airborne droplets. Legionella infection can cause both out-of-hospital and hospital pneumonia.

The following groups of people are most susceptible to legionella pneumonia:

• suffering from chronic alcoholism;
• patients with concomitant chronic bronchopulmonary pathology;
• smoking;
• patients with diabetes mellitus;
• patients with immunodeficiency states;
• receiving immunosuppressants;
• persons working in premises with air conditioners, as well as related work related to the water environment, industrial wastewater, sewerage, shower.

Clinical features of pneumonia caused by legionella

Legionellosis pneumonia affects people of any age, but middle-aged men are more often ill. The incubation period is from 2 to 10 days (an average of 7 days). The disease begins with malaise, general weakness, headaches, muscle, joint pain.

At 2-3 days from the onset of the disease in most patients there is a sharp chill, the body temperature rises to 39-40 C and even higher. From 4-7 days there is a cough at first dry, then with the separation of mucous sputum, often with an admixture of blood, many patients have mucus purulent-purulent. Excess short breath can be observed.

In legionella pneumonia, in most cases, the lower lobes of the lungs, especially the right one, are affected, which in physical research is manifested by blunting percussion sound, crepitus and small bubbling rales.

Often there is involvement of the pleura in the inflammatory process, but not very pronounced. Pleurisy is predominantly fibrinous, manifested by pain in the chest during breathing and coughing and by noise of friction of the pleura. Approximately 50% of patients develop exudative pleurisy, which is manifested by blunt sound during percussion and lack of vesicular breathing in the same zone. However, the amount of exudate in the pleural cavity is usually not large.

Legionellosis pneumonia can often take a severe course with the development of severe respiratory failure, infectious-toxic shock, pulmonary edema. Possible development of the syndrome of disseminated intravascular coagulation with a violation of microcirculation, lung infarctions, gastric, intestinal, uterine bleeding, hemoptysis, hematuria.

With legionella pneumonia, other organs and systems are often affected. There may be gastrointestinal disturbances (vomiting, diarrhea); liver damage (increase in it, hyperbilirubinemia, cytolysis syndrome with an increase in the blood level of alanine aminotransferase); kidneys (microhematuria, proteinuria, possible development of acute renal failure); defeat of the central nervous system (headache, dizziness, blackout, paresthesia, in severe cases - delirium, hallucinations, loss of consciousness).

X-ray manifestations of legionella pneumonia are diverse. In the early stages of the disease, one-sided, non-homogeneous infiltrative shadows are identified, which can be focal or take up a whole lot. Inflammatory infiltrates can be bilateral and often merging.

It should be emphasized that in most cases, interstitial lesions may be observed in 15-25% of cases.

Pleural effusions are often observed, sometimes pulmonary abscesses are formed.

Laboratory data. In the study of peripheral blood leucocytosis is detected (the number of leukocytes rises to 10-15 x 10 ⁷ L), shift of the leukocyte formula to the left, lymphopenia, sometimes thrombocytopenia, a sharp increase in ESR (up to 60-80 mm / h).

Biochemical blood analysis is characterized by hyponatremia, hypophosphatemia, increased activity of aminotransferases, alkaline phosphatase, bilirubin, and lowering of albumin level.

Nosocomial disease of legionnaires

Intrahospital disease of legionnaires is nosocomial outbreaks of the disease with a common source of infection, with a high mortality rate (15-20%).

There are three variants of the clinical course of hospital legionnosis:

• acute pneumonia - characterized by a sharp onset;
• Acute alveolitis - in clinical course resembles acute pneumonia (acute onset, fever, headache, myalgia, general weakness, dry cough, increasing dyspnea). A characteristic auscultative sign is a widespread bilateral loud loud crepitation. Possible prolonged course of acute alveolitis and development of fibrosing alveolitis with progressive respiratory insufficiency;
• acute or chronic bronchitis.

As indicated above, the lethality in the disease of legionnaires is great. The main causes of death are bilateral subtotal lung injury and severe respiratory or hepatic-renal failure, infectious-toxic shock, toxic encephalopathy.

Diagnostic criteria of intrahospital disease of legionnaires

When stating the diagnosis of legionella pneumonia, the following main points are taken into account.

1. The account of epidemiological factors (presence of conditioners, work in baths, showers, etc.).
2. Analysis of the above clinical picture.
3. Use of Nottingham Diagnostic Criteria
4. Isolation of legionella from sputum, transtracheal aspirates, bronchoscopic aspirates, pleural effusion, blood upon sowing on agar with yeast extract and charcoal. The growth of legionella in culture is the most important diagnostic feature, since legionella are not representatives of normal microflora. In legumes spp. Legionella can be detected only in 30-70% of cases.
5. Determination of legionella in sputum and other biological materials by means of immunofluorescence method based on staining of smears. Monoclonal antibodies that are either directly conjugated to a fluorescent dye (direct method) or detected in a smear with secondary fluorescein-labeled antigens (indirect method). The smears are examined under a fluorescent microscope.
6. Determination of legionella in sputum and other biological materials by polymerase chain reaction. The method is based on the detection in the biological material of DNA or RNA fragments specific for this pathogen. The method has an extremely high sensitivity and practically excludes false positive results, but so far it is mainly used in research laboratories. Determination of antibodies to legionella in the patient's blood serum. Confirmation of the diagnosis is a fourfold increase in the antibody titer to a level of at least 1: 128. A titer of at least 1: 128 in a single serum sample of a convalescent patient confirms the diagnosis of legionella pneumonia in the presence of a corresponding clinical picture. However, a diagnostic significant increase in antibody titer is most often observed 3-6 weeks after the onset of the disease. A single determination of antibody titers to legionella has a diagnostic value at a value greater than 1: 1024. Determination of legionella antigens in urine.

Nottingham diagnostic criteria for legionella pneumonia

In the first 24 hours of receipt of the patient	In the next 2-4 days
The previous disease, which occurred with toxicosis and hyperthermia (at less than 39 C for 4-5 days) Cough, diarrhea, impaired consciousness or a combination of these symptoms Lymphocytopenia (lymphocytes less than 10 x 10 9 / L) in combination with leukocytosis (leukocytes not less than 15 x 10 9 / L) Hyponatremia (sodium less than 130 mmol / l)	Radiologic confirmation of seals in the lungs (despite conventional antibiotic therapy) Violation of liver function in the absence of obvious hepatitis - the level of bilirubin or aminotransferase more than 2 times higher than the upper limit of the norm Hypoalbuminemia (albumin level less than 25 g / l)

Treatment of pneumonias caused by legionella

A feature of legionella pneumonia is the intracellular location of the pathogen (inside alveolar macrophages and other cells). The optimal drugs for the treatment of legionella pneumonia are drugs that accumulate in high concentrations inside the phagocytes and penetrate well into the bronchial secretion. Legionella is highly sensitive to macrolides (erythromycin and especially to new macrolides: azithromycin, roxithromycin, clarithromycin, etc.), tetracyclines, fluoroquinolones, rifampicin, trimethoprim, sulfamethoxazole.

The first-line drug is erythromycin. It can be administered orally 0.5 g 4 times a day, but oral administration does not always give stable results and often causes dyspeptic disorders (nausea, vomiting, abdominal pain). Therefore, preference is given to intravenous administration of erythromycin phosphate or erythromycin ascorbate drip 1 g per day (recommendations up to 2-4 g / day are found) in isotonic sodium chloride solution or 5% glucose solution at a concentration of not more than 1 mg / ml.

Intravenous administration of erythromycin is continued for 5-7 days. However, in a number of patients, treatment with erythromycin may prove ineffective due to the absence of a bactericidal effect. In this case it is possible to recommend azithromycin (sumamed), roxithromycin, clarithromycin. Effective tetracyclines, especially doxycycline and minocycline, as well as rifampicin (0.15-0.3 g every 6 hours inside). The intake of these drugs can last 10-14 days. The most pronounced activity with respect to legionella is observed in fluoroquinolones: ciprofloxacin, ofloxacin, nefloxacin, lomefloxacin, fleoxacin, sparfloxacin. In particularly severe cases it is recommended imipenem (thienes).

• Pneumonia - Treatment regimen and nutrition
• Antibacterial drugs for the treatment of pneumonia
• Pathogenetic treatment of pneumonia
• Symptomatic treatment of pneumonia
• Fighting complications of acute pneumonia
• Physiotherapy, exercise therapy, respiratory gymnastics with pneumonia
• Sanatorium treatment and rehabilitation for pneumonia

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