Genetic characteristics of Mycobacterium bovis BCG Thai Red Cross Society strain

Background: Bacillus Calmette-Guerin (BCG) Tokyo 172-1 strain has been used as a parent strain since 1988 by Queen Saovabha Memorial Institute, Thai Red Cross Society to manufacture BCG vaccine in Thailand. In general, the BCG Tokyo strain includes 2 BCG type populations: types I and II. Several studies have found that the type I population is higher than type II. Polymerase chain reaction has shown the presence of 2 types of subpopulations in the BCG Thai Red Cross Society (TRCS) strain. However, the characteristics of all genes from BCG TRCS have not been studied in depth, including whether or not the original features of the BCG Tokyo 172-1 strain are still retained. Objectives: To compare BCG TRCS and BCG Tokyo 172-1 for differences between their genomes. Methods: The whole genome of BCG TRCS was analyzed by next-generation sequencing. Results: BCG TRCS contained 23 different points and was 4 bases less in length than BCG Tokyo 172-1. However, its main features remain similar to those of the original BCG Tokyo 172-1 strain. Conclusions: The changes in the genome may be caused by a variety of factors including the strain of Tokyo 172, vaccine processing, storage, and natural changes in the genome.