Burkholderia pseudomallei, the causative agent of melioidosis, exploits the Bsa type III secretion system (T3SS) to deliver effector proteins into host cells. These effectors manipulate host cell functions; thus, contributing to the ability of the bacteria to evade the immune response and cause disease. Only two Bsa-secreted effectors have been conclusively identified to date. Here, we report the identification of the third B. pseudomallei type III secreted effector protein, designated BopC. BopC is encoded by the bpss1516 gene abutting bpss1517, which encodes its putative chaperone. The genes are located in the close proximity to the bsa T3SS gene cluster of B. pseudomallei K96243 (Fig. 1). BopC was secreted into culture supernatant by the wild-type B. pseudomallei strain, but its secretion was abolished in the bsaZ T3SS mutant. Using pull down and co-purification assays, we confirmed that BopC interacts with its putative chaperone, BPSS1517, in vitro. Furthermore, the first 20 N-terminal amino acids of BopC were found to be sufficient to mediate the T3SS-dependent translocation of a reporter protein from a heterologous enteropathogenic Escherichia coli host into mammalian cells. Finally, bopC mutant was found to be less invasive than the wild-type strain in the epithelial cells.

Burkholderia pseudomallei, the causative agent of melioidosis, is a Gram-negative saprophytic bacterium capable of surviving within phagocytic cells. To assess the role of BopC (a type III secreted effector protein) in the pathogenesis of B. pseudomallei, a B. pseudomallei bopC mutant was used to infect J774A.1 macrophage-like cells. The bopC mutant showed significantly reduced intracellular survival in infected macrophages compared to wild-type B. pseudomallei. In addition, the bopC mutant displayed delayed escape from endocytic vesicles compared with the wild-type strain. This indicates that BopC is important, and at least in part, needed for intracellular survival of B. pseudomallei.

The COVID-19 pandemic led to the suspension of all university courses which was followed directly by the implementation of online learning in Thailand. However, online learning was not suitable for all of Thailand. Rangsit University is a famous private university in Thailand and has been affected by this crisis, so it attempted to eliminate online learning by offering vaccination and antigen rapid screening tests to the students and staff who had to attend the university from July to September 2021. 93.71% of the students and staff from Rangsit University who attended the university from July to September 2021 were vaccinated. Only 1.18% of the students and staff were infected. The vaccines used were CoronaVac and AstraZeneca at 66.02% and 33.98%, respectively. The percentage of individuals that were infected after vaccination did not differ between the two vaccines. The percentage of people infected was 0.31% for CoronaVac and 0.29% for AstraZeneca. Other important factors that influenced the infection rate were the initial symptoms and the environment. Individuals who had initial symptoms and had visited areas with high-risk factors had a high possibility of becoming infected. This research is intended to be useful for risk management during the COVID-19 crisis.