Study on the differences in virulence and growth activity of Mycobacterium tuberculosis isolates from Qinghai region and Southeast China coastal area

Abstract

Objective To investigate the differences in virulence and growth activity of Mycobacterium tuberculosis isolates from Qinghai region and Southeast China coastal area. Methods From March 2015 to August 2016, 212 strains of Mycobacterium tuberculosis were isolated from confirmed patients with tuberculosis, including 84 strains in Qinghai region and 128 in the Southeast China coastal area. The isolates mycobacterium tuberculosis was tested by spoligotyping technique. Drug resistance test was used to detect the drug resistance of the strain. Flow cytometry was used to detect the apoptotic rate and turbidity of the macrophages. The growth curves of the two strains in aerobic and anaerobic environments were plotted. Results SITVITWEB identified 84 strains of Mycobacterium tuberculosis in Qinghai region with allocation to five lineages including Beijing (78.9%), T (7.1%), and H (2.4%), while the remaining strains did not have a matching pattern in the database. SITVITWEB identified 128 strains of Mycobacterium tuberculosis in southeast China coastal area with allocation to three lineages including Beijing (66.7%), MANU (4.8%), T (5.5%), H (1.2%), and LAM (0.8%), while the remaining strains did not have a matching pattern in the database. The single drug resistance, multidrug-resistance and poly-drug-resistance of 84 Mycobacterium tuberculosis isolates in Qinghai region were 14.3%, 29.8%, and 8.3%, respectively. The single drug resistance, multidrug-resistance, and poly-drug-resistance of 128 Mycobacterium tuberculosis isolates in southeast China coastal area were 12.5%, 22.7%, and 2.3%, respectively. There were significant differences in poly-drug-resistance between two regions (χ2=4.048, P=0.044). The results of flow cytometry showed that the apoptotic rate of macrophages infected with representative Mycobacterium tubercu-losis strains isolates in Southeast China coastal area at 6 h, 24 h, and 48 h were significantly higher than that in Qinghai region (P<0.05). The growth curve showed that the growth status of Mycobacterium tuberculosis in aerobic environment was basically similar, but in anaerobic environment, the growth rate of Mycobacterium tuberculosis in Southeast coastal areas was significantly higher than that in Qinghai region (P<0.05). Conclusions The Beijing family is the predominant strain causing the epidemic of tuberculosis in Qinghai region and Southeast China coastal areas, and the strains of Mycobacterium tuberculosis in southeast China coastal areas are more virulent and have stronger viability in anaerobic environment. Key words: Mycobacterium tuberculosis; Virulence; Growth; Genotype; Drug resistance, microbial