Viability of causative pathogen in patients with drug-sensitive and drug-resistant forms of respiratory tuberculosis

Abstract

To predict outcomes of tuberculosis we investigated the viability of Mycobacterium tuberculosis (MTB) in relation to drug resistance of strains and clinical manifestations of tuberculosis. During the study on solid Löwenstein - Jensen medium, we determined the speed, growth rate and drug resistance of MBT in 5945 cultures, isolated from the sputum of patients with pulmonary tuberculosis - residents of the Irkutsk region (2193 -from newly diagnosed patients, 3752 - from previously treated patients). The criterion of high viability of MBT was the growth rate of >100 colonies over 20 days; and low viability corresponded with the growth rate of 30 days. 2171 cultures (36.5 %) had high viability of MBT strains, 3021 (50.8 %) - low, and 753 (12.7 %) cultures had average degree of viability. A high degree of pathogen viability was more often determined in newly diagnosed patients with tuberculosis of intrathoracic lymph nodes (all patients with HIV-infection without antiretroviral therapy), fibrotic-cavernous and infiltrative tuberculosis. Among previously treated patients with tuberculosis the high viability of MBT was often determined in patients with fibrous-cavernous and infiltrative tuberculosis, and caseous pneumonia. Cultures from previously treated patients with tuberculosis of intrathoracic lymph nodes had low degree of viability. The number of drug-sensitive strains was 1992, drug-resistant ones - 3953, including 1430 strains with multidrug resistance. We have found that 37.5 % drug-resistant strains associated with a high degree of viability (multidrug resistance - 38.5 %), it's was more often than the drug-sensitive (35.4 %; p < 0.01).

Keywords

• tuberculosis
• the viability of mycobacterium tuberculosis
• drug resistance
• hiv-infection