No abstract

The 56-kDa type-specific antigen is a major outer membrane protein located on the surface of Orientia species. This 56-kDa antigen has widely applied for evaluation and diagnosis of scrub typhus. However, these antigens are diversity among serotype. Therefore, most of diagnostic test for scrub typhus must be a combination of all types of 56 kDa antigens. In the previous study, we found that the most common genotype was identified in Vietnam belong to Karp, Kato, TA763, Gilliam genotypes. In order to create an ELISA kit for diagnose scrub typhus in Vietnam, these common genotypes are cloned and expressed in E. coli cells for producing recombinant proteins. In this study, a determinant antigen of 1149 bp gene encoding for 56 kDa antigen specific to Karp serotype of O. tsutsugamushi was cloned into pET22b(+) plasmid and expressed in E. coli BL21(DE3) cells. The result indicated that the truncated 56 kDa antigen was successfully expressed in E. coli BL21 cells by inducing with 0.5 mM IPTG in 4 hours. Western blotting showed that HT09 protein reacted with the antiserum against O. tsutsugamushi. This recombinant HT-09 protein is able to use as a specific antigen for developing O. tsutsugamushi diagnostic.

Tuberculosis is still burden in developing countries, including Viet Nam. Molecular techniques such as PCR, Real-time PCR play an important role in tuberculosis diagnostics. Specimens for tuberculosis testing are complex such as sputums, gastric fluids. DNA extraction are commonly performed by commercial kits, with little study about efficacy for tuberculosis testing assays. This study describes efficacy of three kits G-Spin (Intron-Korea), RIBO- sorb (Amplisens-Russia), DNA/RNA Prep (Sacace-Italy), and Salting-out method using basic reagents. Samples were 15 sputums collected from tuberculosis infected cases. As the result, recovered ADN was highest in DNA/RNA Prep, folowed by Salting-out, G-Spin, and last by RIBO - sorb. Oder of purification value was RIBO - sorb, G-Spin, Salting-out, and DNA/RNA Prep. About PCR for 16S gene, 15/15 samples were succeed in G-Spin and DNA/RNA Prep, 14/15 from RIBO-prep, 13/15 from Salting-out. Real-time PCR Mycobacterium tuberculosis (Sacace-Italy) detected 14/15 samples from G-Spin, DNA/RNA Prep, and RIBO-sorb, but Salting-out detected 13/15 samples. Therefore, G-Spin and DNA/RNA Prep show higher efficacy in amplication of 16S gene and Real-time PCR assays for tuberculosis. RIBO- sorb has equal efficacy in Realtime PCR, but more priority in purification. Salting-out perform equally in recovery and purification with commercial kits, but limited in efficacy of Mycobacteria genome amplification.

Rickettsiosis is a zoonotic disease caused by Rickettsiae which are gram negative bacteria, obligate intracellular. These pathogens are transmitted to human through infected ticks, mites, fleas, lice, louse… In this study, The 17kDa and OmpA partial genes of Rickettsia were amplified to detect Rickettsial DNA in buffalo ticks and louse (Haematopinus tuberculatus) collected in Ha Giang province. The PCR products were sequenced, analyzed and build phylogenetic tree by Bioedit, Mega-X softwares; were compared and identified the reference strain sequences by BLAST- NCBI, USA. The results indicated that 14/25 tick samples and 2/14 louse samples were positive for Rickettsia SFG by PCR. Sequence analysis of OmpA gen showed that 14 clone isolated from the tick samples exhibites a 98% - 100% similarity to Rickettsia japonica, whereas 2 clone isolated from the louse samples were 98% similar to Rickettsia massiliae. Thus, our research showed that Rickettsia SFG including Rickettsia japonica and Rickettsia massiliae were detected in ticks and louse, respectively collected in Ha Giang province, Vietnam.

Hepatitis B (HBV), C (HCV), and D (HDV) are common infectious diseases that cause serious health consequences and lead to death due to dangerous complications such as acute liver failure, cirrhosis, and liver cancer. According to The World Health Organization estimates, there were about 354 cases of chronic HBV and HCV infection in 2019. Vietnam is a country that has high rates of HBV infection and an estimated 8.6 million people are infected with HBV. In this study, we identified the prevalence rates of HBV, HCV, and HDV in 1248 serum samples collected from healthy among young adults aged 18 to 29 years old (mean age: 20.3 ± 1, 4) in Thai Nguyen and Da Nang in 2018 by ELISA. We also identified the HBV genotype in HBV-DNA-positive samples, sequenced the preS/S gene, and analyzed the phylogenetic tree. The study result showed that the detection rate of HBsAg antigen is 3.5% and total anti-HBc is 24.9%, the detection rate of anti-HCV is low and the anti-HDV is not decided in the cohort of (18-29 years old) young adults in Thai Nguyen and Da Nang. The phylogenetic analysis showed there is a circulating of genotype B and genotype C. The rate of HBV belonging to the B4 subtype is 78.9% and belonging to the C1 subtype is only 21.1%. 15/19 samples of recombinant HBV detected is the genotype B4/C. The rare mutant G145K belonging to a vaccine escape mutation is identified in one of the HBV samples in Thai Nguyen; the core promoter double mutation A1762T/G1762A are identified in one of the HBV sample; and only one mutation A1762T is identified in one of the HBV sample.