Abstract
Tuberculosis is still a major public health problem in Thailand due to the increased incidence in drug-resistant and multidrug-resistant infections. From the study on multidrug-resistant tuberculosis in Thailand by using whole genome sequence analysis technique, Associate Professor Dr. Angkana Chaisprasert has discovered that there is a clonal outbreak strain in the Kanchanaburi Province (which is now referred to as the "MKR superspreader"). The MKR superspreader belongs to the Beijing family sequence type (ST) 10 genotype and is appeared to have a special ability to spread the infection when compared to that of other strains in Thailand. In this research, our team therefore aimed to identify the mycobacterial and host factors that contribute to the special ability of the MKR superspreader to transmit the infection better than other strains in Thailand. Since one of the main factors affecting the ability of Mtb to spread well from one patient to another depends on its ability to grow at a high rate in the host macrophages such that the host cells will die by necrosis, at which the bacteria will be released outside the cells. When the patient coughs or sneezes, the infectious aerosols will then transmit the Mtb to the other person. The higher the number of bacteria in the infectious aerosols, therefore, will increase the chance of infection to others. In this study, we hypothesized that the MKR superspreader has the special ability to transmit better than other strains because it has the ability to inhibit the defense mechanism of host cells resulting in high growth rate and causes the host cells to undergo necrosis. In year 1, we already confirmed that the MKR superspreader grew at a high rate in host macrophages and caused host cells to undergo necrosis when compared to the other strain. By conducting RNA-sequencing analysis, we also identifed host and mycobacterial genes that may contribute to the higher ability of the MKR superspreader to grow inside host macrophages and cause host cells to undergo necrosis. In year 2, we validated the expression of these genes by qRT-PCR as well as studied their function using the Crispr-dCas9 interference system (specifically developed for mycobacteria) and siRNA knockdown (for host cells) coupled with the phenotypic analysis. The results obtained led to the identification of new drug targets that can be further developed to be used to inhibit the infection by this strain in the future.
