Molecular markers of dihydroartemisinin-piperaquine resistance in northwestern Thailand.

BACKGROUND: Dihydroartemisinin-piperaquine (DHA-PPQ) combination therapy is the current first-line treatment for Plasmodium falciparum malaria in Thailand. Since its introduction in 2015, resistance to this drug combination has emerged in the eastern part of the Greater Mekong Subregion including the eastern part of Thailand near Cambodia. This study aimed to assess whether the resistance genotypes have arisen the western part of country. METHODS: Fifty-seven P. falciparum-infected blood samples were collected in Tak province of northwestern Thailand between 2013 and 2019. Resistance to DHA was examined through the single nucleotide polymorphisms (SNPs) of kelch13. PPQ resistance was examined through the copy number plasmepsin-2 and the SNPs of Pfcrt. RESULTS: Among the samples whose kelch13 were successfully sequenced, approximately half (31/55; 56%) had mutation associated with artemisinin resistance, including G533S (23/55; 42%), C580Y (6/55; 11%), and G538V (2/55; 4%). During the study period, G533S mutation appeared and increased from 20% (4/20) in 2014 to 100% (9/9) in 2019. No plasmepsin-2 gene amplification was observed, but one sample (1/54) had the Pfcrt F145I mutation previously implicated in PPQ resistance. CONCLUSIONS: Kelch13 mutation was common in Tak Province in 2013-2019. A new mutation G533S emerged in 2014 and rose to dominance in 2019. PPQ resistance marker Pfcrt F145I was also detected in 2019. Continued surveillance of treatment efficacy and drug resistance markers is warranted.

Chronic hepatitis B prognostic markers other than pre-treatment viral load predicted composite treatment outcome.

INTRODUCTION: Chronic hepatitis B (CHB) is a globally common infectious disease. Its clinical course is complicated. In Southeast Asia, nucleos(t)ide analogues (NA) are commonly used drugs for CHB treatment. Composite treatment outcome has often been used in CHB clinical practice, but rarely predicted epidemiologically. This study aimed to compare the composite treatment outcome between CHB patients with low and high treatment-naïve viral load, and to identify its predictors METHODOLOGY: This retrospective cohort study followed up 95 CHB patients on NA treatment for a year. Composite treatment outcome was defined as undetectable HBV DNA level, ALT normalization and, HBeAg clearance in the case of HBeAg-positive patients. Multinomial logistic regression analysis was applied to analyze the significant treatment response predictors. RESULTS: Complete composite treatment outcome was achieved by 52% of CHB patients with an initial viral load < 6.5 log 10 copies /ml, but 31% of those had an initial viral load ≥ log 6.5 log 10 copies /ml. Outcome was predicted by HBeAg negativity (adjusted relative risk ratio, aRRR = 11.1, 95 % confidence interval, CI 3-41.3) and ALT normalization within the sixth month of therapy (aRRR = 6.7, CI 1.8-24.9). An elevation of ALT to more than 1.5 times the normal value (40 IU/ml) can lead to an incomplete response on NA therapy (aRRR = 6.2, CI 1.5-26.6.) CONCLUSION: Routine clinical markers other than pre-treatment viral load predicted composite CHB outcome on NA Therapy.