Pulmonary mycobacterial infection is a respiratory infection caused by non–tuberculosis Mycobacterium species. The clinical picture is characterized by the presence of chest pain, productive cough, shortness of breath, hemoptysis, intoxication syndrome. Infections of soft tissues, joints, and bones often occur. The diagnosis is facilitated by laboratory identification of the pathogen, histological and radiological signs. The basis of conservative therapy of pulmonary mycobacteriosis is multicomponent antibiotic therapy, in some cases lung resection in various volumes is indicated.
ICD 10
A31.0 Pulmonary mycobacterial infection
Meaning
Mycobacterioses are opportunistic infections, the causative agents of which are non–tuberculosis (atypical) Mycobacteria (NTM). They occur in the form of tuberculosis–like lesions of the lungs, skin, soft tissues, lymph nodes, joints and bones, sometimes in a disseminated form. The incidence of mycobacteriosis in industrialized countries is 1-2:100,000 and continues to increase constantly. This is due to both improved diagnostics and an increase in the number of patients with deep immunodeficiency and immunosuppression. Mycobacterioses are a multidisciplinary problem relevant for phthisiopulmonology, dermatology, surgery.
Causes of pulmonary mycobacterial infection
Characteristics of the microorganism
The genus Mycobacterium combines pathogenic (pathogens of leprosy, tuberculosis infection), conditionally pathogenic (pathogens of mycobacteriosis) and non-pathogenic mycobacteria (MB). Mycobacteria are rod‒shaped aerobic acid-resistant microorganisms. They are divided into fast-growing (form colonies in less than 7 days) and slow-growing (form colonies in 7 or more days while maintaining an optimal environment and temperature).
To date, more than 140 types of non-tuberculosis MB with varying degrees of virulence have been studied, of which about 40-60 cause human mycobacteriosis. These microorganisms are widespread everywhere, are found in water (including tap water), soil, some of them are parasitic in the body of wild and domestic animals, birds. Many NTMs are immune to disinfectants and chemotherapy drugs (including anti-tuberculosis). Epidemiologically, the greatest danger to humans is:
- M. avium complex (MAC) – cause mycobacteriosis of the lungs (up to 75% of cases), lymphadenitis, disseminated mycobacteriosis;
- M. kansasii – pulmonary, generalized mycobacteriosis;
- M. Xenopi, M. malmoense – respiratory mycobacteriosis;
- M. scrofulaceum – mycobacteriotic lymphadenitis;
- M. Abscessus, M. Chelonei, M. fortuitum – skin and soft tissue infections;
- M. ulcerans – Buruli ulcer;
- M. marinum is an aquarium/swimming pool granuloma.
Mechanism of infection
The study of the ways of transmission of non-tuberculosis MB continues. To date, the likely entrance gates for infection are called the respiratory tract, skin, gastrointestinal tract. Thus, the main mechanisms of infection are inhalation, contact, fecal-oral.
Sources of infection are domestic animals and poultry, water reservoirs (including natural reservoirs, water supply systems, swimming pools), contaminated soil. Possible nosocomial spread of infection with the use of respiratory, anesthesia, dialysis equipment, intravenous catheters, instruments, infected transplants. It is believed that infection of a healthy person from a patient is unlikely, however, there is evidence that transmission of infection from person to person is relevant for HIV-infected patients with cystic fibrosis.
Risk factors
Mycobacterioses mainly affect people with disorders of local and general immunity. Respiratory mycobacterial infection develops mainly in people with background diseases, working in hazardous industries, engaged in the care of farm animals, older than 50 years. The most vulnerable categories for the development of mycobacteriosis of the lungs include patients with the following comorbidities:
- HIV infection:
- drug immunosuppression caused by taking cytostatics, GCS, monoclonal antibodies to TNF-alpha: patients with oncological, autoimmune diseases, recipients of organs and hematopoietic stem cells;
- dysphagia;
- bronchopulmonary diseases: COPD, asthma, pneumoconiosis, sarcoidosis, BEB, tuberculosis, cystic fibrosis;
- general somatic pathology: diabetes, cardiac defects;
- violation of the production of endogenous interferon-gamma, IL-12, vitamin D deficiency.
Vaccination of children with BCG, on the contrary, has a protective effect against NTM, leads to a reduction in the incidence of mycobacteriotic lymphadenitis.
Pathogenesis
In the development of pulmonary mycobacteriosis, the leading role belongs to the aerogenic mechanism of infection, as well as reactivation of dormant infection. When NMB enters the respiratory tract in a healthy person, cellular and humoral defense mechanisms are activated ‒ phagocytosis, production of proinflammatory cytokines (IFNy, IL-12, TNF-α), synthesis of monocytes and CD4 lymphocytes – due to which the pathogen is not eliminated.
In individuals with a deficiency /defects of the immune system, NTMs multiply freely in the respiratory tract, settle in the respiratory bronchioles and alveoli, where the primary pathological focus of pulmonary mycobacteriosis is formed. From there, NTMs penetrate into the lymphatic channel of regional lymph nodes, causing the phenomena of lymphadenitis.
At the next stage, hematogenous dissemination of infection occurs in the lungs with a pronounced inflammatory reaction, the formation of epithelioid giant cell granulomas, the phenomena of endobronchitis and vasculitis. With immunodeficiency, bacteremia develops, and mycobacteriosis infection generalizes.
Classification
The clinical classification of pulmonary mycobacterioses has not been developed. According to the etiological principle, mycobacterioses are distinguished in HIV, immunosuppression, swallowing disorders. Depending on the prevailing radiological changes in clinical pulmonology , the following forms are described:
- Cavity. It is more common in older men with CKD. In the lungs, decay cavities are determined, resembling those in tuberculosis.
- Bronchiectatic. It is more often detected in elderly women without concomitant pulmonary pathology. It differs in the presence of bronchiectasis and bronchiolectasis.
- Focal. It is characterized by the presence of solitary or multiple foci in the absence of clinical symptoms.
Recurrence of mycobacteriosis of the lungs is diagnosed with reactivation of endogenous infection and detection of the same type of mycobacteria, reinfection ‒ in the absence of bacterial excretion during the previous 10-12 months and subsequent typing of a new strain of NTM.
Symptoms of pulmonary mycobacterial infection
The symptoms of mycobacteriosis are diverse and nonspecific. The pulmonary form in most patients resembles a sluggish chronic infection of the respiratory tract. The onset of the disease is more often gradual (the prodromal period can take from 1 month to 2 years), less often acute, sometimes mycobacteriosis is asymptomatic.
The clinical picture consists of respiratory and intoxication syndromes. The most frequent complaints of patients are a prolonged unproductive cough with a meager amount of sputum, episodic hemoptysis, chest pain, shortness of breath. Intoxication syndrome includes weight loss, subfebrile fever, profuse night sweats, palpitations, asthenia.
There is an increase in supra- and subclavian lymph nodes. Often, manifestations of concomitant pulmonary diseases are layered on the clinic of mycobacteriosis. MAS infection is characterized by complaints of abdominal pain, diarrhea.
Complications
The defeat of the respiratory organs of NMB is often complicated by the addition of fungal infection (pulmonary aspergillosis), tuberculosis, nosocomial pneumonia. Against the background of immunodeficiency, the course of mycobacteriosis may become generalized. Extrapulmonary lesions are found in the spleen, liver, intestines, bone marrow, central nervous system. The involvement of lymph nodes (intra-thoracic, mesenteric, retroperitoneal) with the development of purulent lymphadenitis, intra-abdominal and retroperitoneal abscesses is characteristic. Skin infections, soft tissue abscesses, purulent arthritis, osteomyelitis are frequent.
Diagnostics of pulmonary mycobacterial infection
Diagnosis of mycobacterioses is associated with significant difficulties due to their clinical, radiological and morphological similarity with pulmonary tuberculosis. The leading role in carrying out diagnostic measures and interpreting the results obtained belongs to a pulmonologist, a phthisiologist. To verify mycobacterioses ,:
- X-ray diagnostics. With X-ray or CT of the lungs, bilateral decay cavities, infiltrative foci or bronchiectasis are usually visualized (sometimes combined changes are noted). Of the concomitant changes, there is a deformation of the pulmonary pattern, an increase in VGL, calcifications, bullous emphysema, etc.
- Cultural research. Sputum is seeded 3 times on nutrient media, if it is impossible to obtain sputum, bronchial flushes are examined. The etiological diagnosis is considered confirmed with a single positive result of sowing lavage fluid or a double positive sputum sowing. For the selection of a treatment regimen, it is also important to determine drug sensitivity and species identification of NMB, which is carried out using PCR.
- Biopsy. Depending on the clinical situation, tissue samples are taken during bronchoscopy, lymph node biopsy, diagnostic mediastinoscopy or thoracoscopy. The presence of granulomatous inflammation or acid-resistant NMBS indicates in favor of mycobacteriosis of the lungs.
- Tuberculin samples. The role of the Mantoux test in the diagnosis of mycobacteriosis of the lungs remains controversial. However, its negative result with a high probability makes it possible to exclude tuberculosis infection.
- Hematological studies. In patients with verified mycobacteriosis, it is necessary to determine the HIV status, the state of cellular (T-lymphocytes, B-lymphocytes) and humoral (immunoglobulins of classes A, G, M) immunity. To assess the activity of the inflammatory process, blood test with a leukocyte formula and ESR, acute phase markers are examined.
Treatment of pulmonary mycobacterial infection
Etiotropic therapy
The determination of indications for the appointment of antibiotic therapy is another controversial issue in the study of mycobacteriosis. It is believed that with an asymptomatic course, treatment is not necessary, because NMBS are conditional pathogens. According to a number of scientists, it is necessary to approach this issue individually, taking into account the age, concomitant diseases of the patient, the X-ray picture.
When prescribing antibiotic therapy, the choice is made in favor of multicomponent schemes, parenteral administration of drugs, long-term courses. The choice of an antibiotic is made taking into account the type of pathogen:
- in case of MAS infection: macrolides, anti-tuberculosis drugs, aminoglycosides;
- in M.kansasii: anti-tuberculosis antibiotics, macrolides, sulfonamides, aminoglycosides, fluoroquinolones;
- in M.xenopi: ansamycins, macrolides, fluoroquinolones, aminoglycosides;
- in M. fortuitum: fluoroquinolones, sulfonamides, macrolides, aminoglycosides, cephalosporins;
- with M. fortuitum, M. abscessus: tetracyclines, carbapenems, etc.
Pathogenetic and symptomatic therapy
Smoking cessation and proper nutrition are recommended. Pathogenetic treatment involves the appointment of bronchodilators (inside, inhalation, nebulizer therapy), mucoactive, immunotropic drugs. In case of unsatisfactory drainage function of the bronchial tree, sanitization bronchoscopy is indicated.
NSAIDs, glucocorticoids, vitamins, antiplatelet agents, and antioxidants may be indicated to reduce the inflammatory process. From non-drug measures, breathing exercises, percussion massage, oxygen therapy, physiotherapy procedures are useful.
Surgical treatment
If radical rehabilitation of the respiratory tract is impossible, and there are persistent morphological changes in the lungs, the question of surgical methods for the treatment of mycobacteriosis is raised. The volume of lung resection can be variable: from wedge-shaped excision, segmental and lobectomy to pneumonectomy and pleuropneumonectomy. Preoperative and postoperative antimicrobial chemotherapy is mandatory. After completion of treatment, microbiological and X-ray monitoring is recommended for a year.
Prognosis and prevention
Mycobacterioses are potentially lethal diseases, especially for immunocompromised patients. Mortality in this group is 14%. Treatment is carried out in long courses (from 12 to 24 months), complicated by the drug resistance of mycobacteria, difficulties in selecting a rational scheme of antibiotic therapy. A combination of conservative and surgical tactics is often required.
A number of treated patients have relapses of mycobacteriosis over the next 5 years, so such patients need long-term, sometimes lifelong dispensary supervision. Since the disease most often occurs in patients with immunodeficiency and concomitant pathologies of the respiratory system, it is necessary to take care of the prevention of these pathologies. It is necessary to carry out anti-epidemic measures in health facilities, monitoring the health status of workers of harmful industries.