Nontuberculous mycobacterioses: epidemiology, clinic and possibilities of laboratory diagnostics in modern conditions

Abstract

Introduction. Today there are more than 150 species of nontuberculous mycobacteria (NTMB) known, of which 99 were registered in Europe. Due to the similar clinical picture with tuberculosis, mycobacterioses are difficult to diagnose and often occur with TB as a mixed infection. Also, there are cases of NTMB detection in the sputum of persons previously suffered with tuberculosis, which can lead to a false diagnosis of recurrent disease. Currently, the role of atypical mycobacteria in human pathology is increasing. Atypical mycobacteria are characterized by a wide spectrum of sustainability and potential pathogenicity to humans and animals. It is generally accepted that the reservoir of infection are animals and the environment (water, soil). NTMB presence in water can lead to the erroneous diagnosis of mycobacteriosis due to laboratory contamination of samples with nontuberculous mycobacteria from the outside.Moreover recently it has been found the possibility of transferring NTMB from person to person on the background of existing lung disease. For many types of infections reservoir still has not been found. Aim of this work was to study identified in the Kharkiv region cases of non-tuberculous mycobacterioses, features of their clinical manifestations and laboratory diagnostic options. Materials and Methods. We examined 32 patients (25 men and 7 women), residents of Kharkiv and Kharkiv region, Ukraine, who were diagnosed with "non-tuberculous mycobacteriosis of lungs" during 2014-2016. Patients were examined with routine diagnostic algorithm for TB. Nontuberculous mycobacteriosis was diagnosed on the basis of NTMB growth in BACTEC system, after which the diagnosis was verified by the following criteria:

1. Smear: the absence of formation of Cord-factor (in the smear NTMB are located scattering); 2. Negative immunoassay (ID-test); 3. Negative GeneXpert MTB/RIF Then non-tuberculous mycobacteria were identificated by investigation on solid media. They were divided on groups of susceptible causative agents according to Runnyon classification and the modified classification, approved by the Order Ministry of Health of Ukraine №45 from 06.02.2002, which takes into account the NTMB growth rate, character and color of colonies. Results and discussion. In all 32 reported cases infiltrative changes were identified radiographically. In 13 patients (40.6%) cavities were found. In addition in smear of 10 patients (31.2%) was found scant bacterial excretion, 2 (6.2%) - moderate, and 1 (3.1%) - massive. According to the results of culture NTMB were identified.Chromogenic slow-growing non-tuberculous mycobecteria prevailed (65,4%). Another causative agents belonged to M. avium complex. The heaviest lesions were caused by chromogenic slow-growing non-tuberculous mycobecteria, as 41,1% of these patients had extensive lung damage, and 64,7%% - destruction of lung tissue.Radiographic changes correlated with the severity of clinical manifestations. Also in this group most often was founddetectable by smear bacterial excretion, including moderate and massive. In our patients prevailed cavernous form which is is typical for smoking middle-aged men, often develops on the background of previous lung disease - cystic fibrosis (M. abscessus), COPD, bronchoectatic disease, tuberculosis in the past, aspergillosis (M. xenopi), as well as on the background of HIV infection and drug treatment that suppress the immune system (corticosteroids, TNF-alpha inhibitors). Clinical and radiographic this form is almost indistinguishable from pulmonary tuberculosis (infiltrates in upper lobeswith formationof cavities), more severe, often with a syndrome of intoxication, cough, shortness of breath, sometimes hemoptysis. Without treatment, the disease progresses rapidly and leads to formation of large cavities in the lungs and respiratory failure. The most common pathogens that cause such clinical and radiological picture are M. kansasii, M. xenopi and Mycobacterium avium complex. Conclusions. In Kharkiv regionthere is an increase of non-tuberculous mycobacterioses, but their diagnostics is difficult due to the lack of diagnostic capabilities: it is impossible to perform CT examination in all patients, no possibility of reliable identification of the type of pathogen (no DNA strip technology, tablet technology, DNA sequencing, high-performance liquid chromatography). Among the identified cases of mycobacterioses prevailed chromogenic slow-growing NTMB. Clinical and radiographic pattern was characterized by severe thoracic (cough, shortness of breath) and intoxication (fever, weight loss, weakness) complaints and extensive lesions ofpulmonary system. Also in this group was often founddetectable by smear bacterial excretion, including massive one. It was noted that often mycobacterioses developed on the background of existing pulmonary disease. Failure to conduct complete laboratory diagnostics, identification of pathogen and determination of its individual sensitivity to drugs significantly complicates prescribing of adequate chemotherapy regimens. In this regard, we consider a priority the development of standards for diagnosis and treatment of non-tuberculous mycobacterioses and further strengthening the capacity of laboratory diagnostics.