Differential expression of sigma factor of Mycobacterium tuberculosis under in vivo infection and in vitro culture conditions / 公共卫生与预防医学

ABSTRACT

Objective To investigate the gene expression of sigma factors in vivo, and to explore the sigma factors that may be closely related to the virulence of pathogenic Mycobacterium tuberculosis Methods Tuberculosis (TB) patients diagnosed in the outpatient department of Tianjin Tuberculosis Control Center from January to December 2018 were selected, and 20 sputum-positive specimens were randomly selected from TB patients confirmed with Xpert-positive for the present study. Two immediate sputum specimens were collected from each case of pulmonary tuberculosis before treatment, one for RNA extraction and one for in vitro culture. In vitro cultured strains in the logarithmic phase of growth were harvested for RNA extraction. The specific primers for 13 sigma factors were designed. The differential expression of the 13 sigma factors between sputum isolates and in vitro cultured strains was analyzed by fluorescence quantitative PCR. Taking ribosomal 16s as the reference gene, the transcription level of sigma factors was analyzed by 2ΔCt. Using the stably expressed sigA as the control reference, the expression differences of other sigma factors were analyzed by one-way ANOVA. Results Within 0 days, stress-associated sigma factors have a different expression profile in clinical isolate strains vs H37Rv or in vitro. All the sigma factors induced up regulation in sputum ,while no difference transcription between clinical isolate strains vs H37Rv（P＞0.05）. When compared to in vitro culture ,only sigM transcript highest in sputum(P＜0.05). Conclusion SigM plays an important role in the initial stages of bacterial infection, but its exact role is unclear.We assumed it could have a role in the interplay between the host immune defenses and the bacterial escape mechanisms.