Growth Stimulation, Phosphate Resolution, and Resistance to Fungal Pathogens of Some Endogenous Fungal Strains in the Rhizospheres of Medicinal Plants in Vietnam.

Endophytic fungi are recognized for their many potential applications in agriculture, such as supporting cropland expansion and increasing the yield and resistance of plants by creating antibiotics that inhibit the growth of pathogenic microorganisms. In addition, they can produce enzymes that break down hard-to-solubilize substances within soil, dissolve phosphates, fix nitrogen, reduce metals, and produce hormones that promote plant growth (auxin, cytokinin, and gibberellins) to keep crops healthy. In this report, three strains of endophytic fungi, namely, N1, N2, and N3, were isolated from the roots of Stevia rebaudiana (Bert.) Hemsl., Polyscias fruticosa, and Angelica dahurica in some localities in Vietnam. Through a screening process, it was found that they can produce high levels of indole acetic acid (IAA), resolve phosphates, and resist disease, and they were selected to as an alternative to chemical fertilizers to make probiotics in order to increase medicinal plant yields. The results show that the three strains of fungi have the ability to degrade phosphate to 341.90, 1498.46, and 390.79 ppm; the content of IAA produced in the culture medium reached 49.00, 52.35, and 33.34 ppm. Based on some morphological characteristics and an internal transcribed spacer gene sequence analysis of the fungal strains, N1, N2, and N3 were named Penicillium simplicissimum CN7, Talaromyces flavus BC1, and Trichoderma konilangbra DL3, respectively, which have the ability to inhibit the growth of pathogenic fungal strains, such as fungus C. gloeosporioides (CD1), fungus F. oxysporum, fungus L. theobromae N13, and N. dimidiatum. They grow significantly over a period of 5 to 6 days.

Challenges for ticks and tick-borne diseases research in Southeast Asia: Insight from the first international symposium in Cambodia.

BACKGROUND: Ticks, as critical vectors of a variety of pathogens, pose a significant public health challenge globally. In Southeast Asia (SEA), ticks are responsible for transmitting a diverse array of pathogens affecting humans and animals. The geographical and ecological diversity of SEA provides a unique environment that supports a wide range of tick species, which complicates the management and study of tick-borne diseases (TBDs). METHODOLOGY/PRINCIPAL FINDINGS: This article synthesizes findings from the first international symposium on ticks and TBDs in Southeast Asia, held in Phnom Penh on June 22 and 23, 2023. It highlights regional efforts to understand tick ecology and pathogen transmission. This paper proposes to present a summary of the various presentations given during the symposium following 3 main parts. The first one is devoted to the state of knowledge regarding ticks and TBDs in SEA countries, with presentations from 6 different countries, namely Cambodia, Indonesia, Laos, Malaysia, Thailand, and Vietnam. The second part focuses on the development of new research approaches on tick-borne pathogens (TBPs) and TBDs. The last part is a summary of the round table discussion held on the final day, with the aim of defining the most important challenges and recommendations for researches on TBP and TBD in the SEA region. CONCLUSIONS/SIGNIFICANCE: Key topics discussed include advancements in diagnostic tools, such as MALDI-TOF MS and proteomics, and the development of sustainable strategies for tick management and disease prevention. The symposium facilitated the exchange of knowledge and collaborative networks among experts from various disciplines, promoting a unified approach to tackling TBDs in the region. The symposium underscored the need for enhanced surveillance, diagnostics, and inter-regional cooperation to manage the threat of TBDs effectively. Recommendations include the establishment of a regional database for tick identification and the expansion of vector competence studies. These initiatives are crucial for developing targeted interventions and understanding the broader implications of climate change and urbanization on the prevalence of TBDs.

Reduction in Plasmodium falciparum Pfk13 and pfg377 allele diversity through time in southern Vietnam.

BACKGROUND: Plasmodium falciparum has acquired resistance to artemisinin in Southeast Asia, with mutations in the P. falciparum Kelch-13 (Pfk13) gene associated with the resistance phenotype. The widespread use of Artemisinin-based combination therapy (ACT)s in Southeast Asia has led to the selection and spread of parasites carrying mutations in Pfk13. We characterised the allele diversity of Pfk13 and pfg377, an artemisinin-resistance neutral polymorphic gene, in parasite DNA extracted human blood from in southern Vietnam in 2003, 2012, 2015 and 2018. METHOD: This study was conducted in Bu Gia Map commune, Binh Phuoc province, Vietnam, from May 2018 to January 2019. Twenty-four samples from 2018 to 2019, 30 from 2003, 24 from 2012 and 32 from 2015 were analysed. Malaria-infected human blood was collected by finger-prick and used for molecular analysis. A nested-PCR targeting the small subunit ribosomal RNA gene was used for Plasmodium species identification, followed by amplification and nucleotide sequencing of Pfk13 and region 3 of pfg377. Archived blood samples collected in the same region in 2012 and 2015 were also analysed as above for comparison. RESULTS: The genetic diversity of Pfk13 and pfg377 was lower in 2018-2019 compared to 2012 and 2015. The number of distinct Pfk13 mutants decreased from three in 2012 and 2015, P553L, V568G and C580Y, to one, C580Y in 2018-2019. In 2018-2019, the frequency of C580Y mutant strains was 71% (17/24 isolates). All samples were wild type in 2003. In 2012 and 2015, there were single-strain infections as well as co-infections with two mutant strains or with mutant and wild strains, whereas there were no co-infections in 2018. pfg377 allele diversity decreased from five alleles in 2012 to two alleles in 2018-2019. CONCLUSION: The genetic diversity of P. falciparum was reduced at the two genetic loci surveyed in this study, Pfk13 and pfg377. In the case of the former gene, we observed an increase in the prevalence of parasites carrying the C580Y gene, known to confer reduced susceptibility to ACTs. The reduction in the diversity of pfg377 may be linked to the clonal expansion of parasite strains carrying the C580Y mutation, leading to an overall reduction in parasite genetic diversity across the population.

Impact of insecticide-treated nets on wild pyrethroid resistant Anopheles epiroticus population from southern Vietnam tested in experimental huts.

BACKGROUND: In this study, the efficacy of insecticide-treated nets was evaluated in terms of deterrence, blood-feeding inhibition, induced exophily and mortality on a wild resistant population of Anopheles epiroticus in southern Vietnam, in order to gain insight into the operational consequences of the insecticide resistance observed in this malaria vector in the Mekong delta. METHOD: An experimental station, based on the model of West Africa and adapted to the behaviour of the target species, was built in southern Vietnam. The study design was adapted from the WHO phase 2 guidelines. The study arms included a conventionally treated polyester net (CTN) with deltamethrin washed just before exhaustion, the WHO recommended long-lasting insecticidal net (LLIN) PermaNet 2.0 unwashed and 20 times washed and PermaNet 3.0, designed for the control of pyrethroid resistant vectors, unwashed and 20 times washed. RESULTS: The nets still provided personal protection against the resistant An. epiroticus population. The personal protection ranged from 67% for deltamethrin CTN to 85% for unwashed PermaNet 3.0. Insecticide resistance in the An. epiroticus mosquitoes did not seem to alter the deterrent effect of pyrethroids. A significant higher mortality was still observed among the treatment arms despite the fact that the An. epiroticus population is resistant against the tested insecticides. CONCLUSION: This study shows that CTN and LLINs still protect individuals against a pyrethroid resistant malaria vector from the Mekong region, where insecticide resistance is caused by a metabolic mechanism. In the light of a possible elimination of malaria from the Mekong region these insights in operational consequences of the insecticide resistance on control tools is of upmost importance.

Prevalence of human and non-human primate Plasmodium parasites in anopheline mosquitoes: a cross-sectional epidemiological study in Southern Vietnam.

BACKGROUND: Human malaria is a major threat in rural communities of central Vietnam. Anopheles dirus and Anopheles minimus species are critical malaria vectors in Vietnam, which transmit Plasmodium parasites. However, the entomological aspects of malaria transmission in some of the central provinces of Vietnam remain unexplored. Hence, a cross-sectional entomological survey was carried out to identify the malaria vector species and the transmission of Plasmodium parasites in seven endemic provinces of Vietnam. METHODS: Mosquitoes were collected from seven provinces, Gia Lai, Khanh Hoa, Phu Yen, Ninh Thuan, Binh Thuan, Dong Nai, and Binh Phuoc. The collection was conducted for four to eight consecutive nights using three established methods, indoor and outdoor human landing catches and light trap method. Nested-PCR analysis was performed to detect the Plasmodium species in the separated thorax and the abdomen of the individual mosquitoes. RESULTS: A total of 2278 mosquitoes belonging to one of the four species of anopheline mosquitoes, An. dirus, An. maculatus, An. aconitus, and An. minimus were collected. Among the collected mosquitoes, 1398 were analysed using nested-PCR, of which, 40 mosquitoes were positive for Plasmodium parasites. Most of these parasites were detected in the samples from the thorax region, followed by the abdominal portion. The parasites were detected in both the thorax and abdomen of An. dirus. Seven species of Plasmodium parasites were detected during the analysis, of which, Plasmodium inui was the most common species, followed by Plasmodium falciparum, Plasmodium vivax, Plasmodium cynomolgi, Plasmodium coatneyi, Plasmodium knowlesi, and Plasmodium fieldi. Out of the 49 positive samples, 12 showed mixed infections. Co-infection of P. inui with human and other non-human primate Plasmodium species was common. CONCLUSIONS: This study demonstrated the presence of human and non-human primate Plasmodium infection in An. dirus, a predominant malarial vector. Further, we showed that An. maculatus and An. minimus species also take part in malarial transmission. This might potentially lead to an alarming situation conducive for the emergence of novel zoonotic malaria.

Characterising residual malaria transmission in forested areas with low coverage of core vector control in central Viet Nam.

BACKGROUND: Despite great success in significantly reducing the malaria burden in Viet Nam over recent years, the ongoing presence of malaria vectors and Plasmodium infection in remote forest areas and among marginalised groups presents a challenge to reaching elimination and a threat to re-emergence of transmission. Often transmission persists in a population despite high reported coverage of long-lasting insecticidal nets (LLINs), the mainstay control method for malaria. To investigate what factors may contribute to this, a mixed-methods study was conducted in Son Thai commune, a community in south-central Viet Nam that has ongoing malaria cases despite universal LLIN coverage. A cross-sectional behavioural and net-coverage survey was conducted along with observations of net use and entomological collections in the village, farm huts and forest sites used by members of the community. RESULTS: Most community members owned a farm hut plot and 71.9% of adults aged 18+ years sometimes slept overnight in the farm hut, while one-third slept overnight in the forest. Ownership and use of nets in the village households was high but in the farm huts and forest was much lower; only 44.4% reported regularly using a bednet in the farm and 12.1% in the forest. No primary anopheline species were captured in the village, but Anopheles dirus (s.l.) (n = 271) and An. maculatus (s.l.) (n = 14) were captured as far as 4.5 km away in farm huts and forest. A high proportion of biting was conducted in the early evening before people were under nets. Entomological inoculation rates (EIR) of An. dirus (s.l.) were 17.8 and 25.3 infectious bites per person per year in the outdoor farm hut sites and forest, respectively, for Plasmodium falciparum and 25.3 in the forest sites for P. vivax. CONCLUSIONS: Despite high net coverage in the village, gaps in coverage and access appear in the farm huts and forest where risk of anopheline biting and parasite transmission is much greater. Since subsistence farming and forest activities are integral to these communities, new personal protection methods need to be explored for use in these areas that can ideally engage with the community, be durable, portable and require minimal behavioural change.

Fabrication and vibration characterization of curcumin extracted from turmeric (Curcuma longa) rhizomes of the northern Vietnam.

In this report, we present the research results on using the conventional method and microwave technology to extract curcuminoid from turmeric roots originated in different regions of Northern Vietnam. This method is simple, yet economical, non-toxic and still able to achieve high extraction performance to get curcuminoid from turmeric roots. The detailed results on the Raman vibration spectra combined with X-ray powder diffraction and high-performance liquid chromatography/mass spectrometry allowed the evaluation of each batch of curcumin crystalline powder sample received, under the conditions of applied fabrication technology. Also, the absorption and fluorescence spectroscopies of the samples are presented in the paper. The information to be presented in this paper: absorption and fluorescence spectroscopies of the samples; new experimental study results on applied technology to mass-produce curcumin from turmeric rhizomes; comparative study results between fabricated samples and marketing curcumin products-to state the complexity of co-existing crystalline phase in curcumin powder samples. We noticed that, it is possible to use the vibration line at ~959 cm(-1)-characteristic of the ν C=O vibration, and the ~1625 cm(-1) line-characteristic of the ν C=O and ν C=C vibration in curcumin molecules, for preliminary quality assessment of naturally originated curcumin crystalline powder samples. Data on these new optical spectra will contribute to the bringing of detailed information on natural curcumin in Vietnam, serving research purposes and applications of natural curcumin powder and nanocurcumin in Vietnam, as well as being initial materials for the pharmaceutical, cosmetics or functional food industries.

Preparation of Gold-Silver Alloy Nanoparticles Supported on NiCo2O4 Spinel Oxides for the Treatment of CO in Atmosphere.

Heterometallics are an important class of catalysts. Alloy nanoparticles have higher activities than monometallic counterparts in catalysis because of the synergistic effects between the two metals. The Ni-Co composition, which is a typical alloy chemical composition, has a remarkable effect on catalytic activity. Ni-Co mixed oxides were characterized by thermal effect, X-ray diffraction, energy dispersive X-ray spectroscopy, Scanning Electron Microscope and BET specific surface area techniques. X-ray diffraction show that the formation of small spinel oxides nanoparticles. Very small amounts of gold-silver alloy nanoparticles deposited on such mixed oxides improve the catalytical activity for CO oxidation.

Experimental Determination of the Fluorescence Quantum Yield of Semiconductor Nanocrystals.

Many studies have considered the luminescence of colloidal II-VI nanocrystals, both in solution at a collective scale and at an individual scale by confocal microscopy. The quantum yield is an important figure of merit for the optical quality of a fluorophore. We detail here a simple method to determine the quantum yield of nanocrystals in solution as a function of the absorption. For this purpose, we choose rhodamine 101 as a reference dye to measure the nanocrystal fluorescence quantum yield. The influence of the concentration on quantum yield is therefore studied for both the reference and the solutions of nanocrystals and is found to be critical for the acuity of the method. Different types of nanocrystals are studied to illustrate different quantum yield evolutions with the concentration.