Is nontuberculous mycobacteria serious?

Many people are unfamiliar with the condition of non-tuberculous mycobacteria and do not know what kind of condition it is. Therefore, even if it occurs, they do not know whether it is serious. But in fact, as long as this condition occurs, there is a possibility of worsening. Severe patients will feel that their bodies are always having fever symptoms, and their weight will be reduced or even hemoptysis.

① Clinical symptoms and signs: Cough and fatigue are common. Patients with more severe conditions may have fever, weight loss, hemoptysis and shortness of breath. Patients with underlying diseases may have worsening clinical symptoms.

②Exclude other diseases: such as tuberculosis, tumor, and histoplasmosis.

(2) X-ray standards:

① Infiltrative lesions with or without nodular lesions (lasting ≥2 months or with progression); cavitary lesions; single or multiple nodules.

② HRCT shows multiple small nodules or multifocal bronchiectasis with or without small pulmonary nodules.

(3) Bacteriological standards:

① At least 3 sputum or bronchial lavage specimens within 1 year, 3 of which are culture-positive and AFB smear-negative, or 2 are culture-positive and 1 is AFB smear-positive.

② If only one bronchial lavage specimen is obtained and no sputum specimen is obtained, the culture is positive and the smear is positive at the same time.

③ If the sputum or bronchial lavage fluid specimens indicate that the diagnosis cannot be confirmed or other diseases have not been excluded, bacterial culture and histopathological examination of bronchial biopsy or lung biopsy are positive.

Risk factors for the disease in HIV-seronegative patients include local immunosuppression such as alcoholism, bronchiectasis, cyanotic heart disease, cystic fibrosis, pulmonary fibrosis, smoking, and chronic obstructive pulmonary disease. Severe systemic immunosuppression, such as leukemia, lymphoma, organ transplantation and other immunosuppressive therapy, HIV serological test positive, CD4 <200.

Since many nontuberculous mycobacterium strains are resistant to commonly used drugs such as isoniazid and streptomycin, but are sensitive to rifampicin to a certain extent, it is now generally recommended to use rifampicin, ethambutol and isoniazid in combination. Mycobacterium ulcerans is only sensitive to aminoglycoside anti-tuberculosis drugs such as kanamycin.

However, avian-intracellulare Mycobacterium has strong drug resistance; it has been reported that all 23 strains isolated were resistant to the above-mentioned drugs; and new erythromycins that have been structurally modified, such as clarithromycin, have excellent anti-tuberculosis activity in vivo and in vitro, can destroy cell walls and cell membrane structures, and have a blood culture clearance rate of 62%-98% for avian-intracellulare Mycobacterium.

Nontuberculous mycobacteria often appear in L form after treatment, with increased drug resistance, and some cannot be cured after years of treatment. Moreover, the L type is often not easy to sensitize lymphocytes due to the lack of cell wall lipids, and the tuberculin test may be negative, so more attention should be paid during diagnosis and treatment.