Pneumonias caused by legionellae: causes, symptoms, diagnosis, treatment

Currently, more than 30 types of legionella have been described, 19 of which cause pneumonia in humans. The most common is Legionella pneumophila. Legionella pneumophila was first isolated in 1977. This microorganism was named after the American Legion, among whose conference participants an epidemic of pneumonia broke out.

Legionella are gram-negative bacteria, they are not part of the physiological flora of humans, are widespread in the aquatic environment, live in air conditioning systems, ventilation, in plumbing in showers, baths, water heaters, in lakes, rivers, streams. The main sources of infection outbreaks are aerosols containing legionella from air conditioning systems, as well as in baths, showers. There are indications that legionella can also be found in drinking water flowing through contaminated taps, as well as in the sewage system. They have also been found in artificial thermal reservoirs, irrigation structures.

Legionella pneumophila enters the lungs through airborne droplets. Legionella infection can cause both community-acquired and hospital-acquired pneumonia.

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

• suffering from chronic alcoholism;
• patients with concomitant chronic bronchopulmonary pathology;
• smokers;
• patients with diabetes;
• patients with immunodeficiency states;
• receiving immunosuppressants;
• persons working in air-conditioned rooms, as well as those whose work involves the aquatic environment, industrial wastewater, sewage, and showers.

Clinical features of pneumonia caused by legionella

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

On the 2nd-3rd day from the onset of the disease, most patients experience severe chills, body temperature rises to 39-40 C and even higher. From the 4th-7th day, a cough appears, initially dry, then with the separation of mucous sputum, often with an admixture of blood, in many patients the sputum is mucopurulent. Pronounced shortness of breath may be observed.

In Legionella pneumonia, in most cases the lower lobes of the lungs are affected, especially the right one, which during physical examination is manifested by dullness of percussion sound, crepitus and fine bubbling rales.

Often, the pleura is involved in the inflammatory process, but not very clearly. Pleurisy is predominantly fibrinous, manifested by chest pain when breathing and coughing and pleural friction noise. Approximately 50% of patients develop exudative pleurisy, which is manifested by a dull sound on percussion and the absence of vesicular breathing in the same area. However, the amount of exudate in the pleural cavity is usually not large.

Legionella pneumonia can often take a severe course with the development of severe respiratory failure, infectious-toxic shock, pulmonary edema. The development of disseminated intravascular coagulation syndrome with impaired microcirculation, pulmonary infarctions, gastric, intestinal, uterine bleeding, hemoptysis, hematuria is possible.

Legionella pneumonia often affects other organs and systems. Gastrointestinal disorders (vomiting, diarrhea); liver damage (enlargement, hyperbilirubinemia, cytolysis syndrome with increased alanine aminotransferase levels in the blood); kidney damage (microhematuria, proteinuria, possible development of acute renal failure); damage to the central nervous system (headache, dizziness, loss of consciousness, paresthesia, in severe cases - delirium, hallucinations, loss of consciousness).

X-ray manifestations of legionella pneumonia are varied. In the early stages of the disease, unilateral non-homogeneous infiltrative shadows are detected, which can be focal in extent or occupy an entire lobe. Inflammatory infiltrates can be bilateral and often merge.

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

Pleural effusions are observed quite often, and sometimes pulmonary abscesses form.

Laboratory data. When examining peripheral blood, leukocytosis is detected (the number of leukocytes increases to 10-15 x 10 ⁷ l), a shift in 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 decreased albumin levels.

Nosocomial Legionnaires' Disease

Nosocomial Legionnaires' disease is a nosocomial outbreak 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 nosocomial legionellosis:

• acute pneumonia - characterized by an acute onset;
• acute alveolitis - in its clinical course resembles acute pneumonia (acute onset, fever, headache, myalgia, general weakness, dry cough, increasing dyspnea). A characteristic auscultatory sign is widespread bilateral loud crepitation. A protracted course of acute alveolitis and subsequent development of fibrosing alveolitis with progressive respiratory failure are possible;
• acute or chronic bronchitis.

As stated above, the mortality rate for Legionnaires' disease is high. The main causes of death are bilateral subtotal lung damage and severe respiratory or hepatorenal failure, infectious toxic shock, and toxic encephalopathy.

Diagnostic criteria for nosocomial legionnaires' disease

When diagnosing Legionella pneumonia, the following main points are taken into account.

1. Taking into account epidemiological factors (presence of air conditioners, work in bathrooms, showers, etc.).
2. Analysis of the above clinical picture.
3. Using the Nottingham diagnostic criteria
4. Isolation of Legionella from sputum, transtracheal aspirates, bronchoscopic aspirates, pleural effusion, blood when cultured on agar with yeast extract and charcoal. The growth of Legionella in culture is the most important diagnostic sign, since Legionella are not representatives of normal microflora. Legionella can be detected in sputum cultures only in 30-70% of cases.
5. Determination of legionella in sputum and other biological materials using the immunofluorescence method based on staining smears with monoclonal antibodies that are either directly conjugated with a fluorescent dye (direct method) or are detected in the smear by secondary fluorescein-labeled antigens (indirect method). Smears are examined under a fluorescent microscope.
6. Detection of Legionella in sputum and other biological materials using polymerase chain reaction. The method is based on the detection of DNA or RNA fragments specific to a given pathogen in the biological material. The method has an extremely high sensitivity and virtually eliminates false positive results, but is currently used primarily in research laboratories. Detection of antibodies to Legionella in the patient's blood serum. A fourfold increase in the antibody titer to a level of at least 1:128 is considered confirmation of the diagnosis. A titer of at least 1:128 in a single serum sample of a recovering patient confirms the diagnosis of Legionella pneumonia in the presence of an appropriate clinical picture. However, a diagnostically significant increase in the antibody titer is most often noted 3-6 weeks after the onset of the disease. A single determination of the antibody titer to Legionella has diagnostic value at a value of more than 1:1024. Detection of Legionella antigens in urine.

Nottingham diagnostic criteria for legionella pneumonia

In the first 24 hours of the patient's admission	In the next 2-4 days
Previous illness, accompanied by toxicosis and hyperthermia (less than 39 C for 4-5 days) Cough, diarrhea, confusion, 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)	X-ray evidence of pulmonary consolidation (despite conventional antibiotic therapy) Liver dysfunction in the absence of obvious hepatitis - bilirubin or aminotransferase levels more than 2 times the upper limit of normal Hypoalbuminemia (albumin level less than 25 g/l)

Treatment of pneumonia 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 phagocytes and penetrate well into bronchial secretions. 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 used orally at 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 by drip at 1 g per day (there are recommendations for up to 2-4 g per day) in isotonic sodium chloride solution or 5% glucose solution at a concentration of no more than 1 mg/ml.

Intravenous administration of erythromycin is continued for 5-7 days. However, in some patients, treatment with erythromycin may be ineffective due to the lack of a bactericidal effect. In this case, azithromycin (sumamed), roxithromycin, clarithromycin can be recommended. Tetracyclines, especially doxycycline and minocycline, as well as rifampicin (0.15-0.3 g every 6 hours orally) are quite effective. These drugs can be taken for 10-14 days. The most pronounced activity against legionella is observed in fluoroquinolones: ciprofloxacin, ofloxacin, nefloxacin, lomefloxacin, fleroxacin, sparfloxacin. In particularly severe cases, imipenem (tienam) is recommended.

• Pneumonia - Treatment regimen and nutrition
• Antibacterial drugs for the treatment of pneumonia
• Pathogenetic treatment of pneumonia
• Symptomatic treatment of pneumonia
• Combating complications of acute pneumonia
• Physiotherapy, exercise therapy, breathing exercises for pneumonia
• Sanatorium and resort treatment and rehabilitation for pneumonia

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