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Outbreaks of the Southern rice black-streaked dwarf virus (SRBSDV) have caused significant losses in many rice-growing areas in Vietnam, especially in both North and Central Vietnam in recent years. To detect the virus, traditional reverse transcription polymerase chain reaction (RT-PCR) methodology and immunoassays are currently employed. RT-PCR is accurate but requires expensive chemicals and instruments, as well as complex procedures that limit its applicability for field tests. To develop a cheaper, simpler, and reliable SRBSDV diagnosis assay based on the dot-enzyme-linked immunosorbent assay (dot-ELISA) method, anti-SRBSDV polyclonal antibodies were produced by using the antigens derived from the P10 coat protein of SRBSDV, which was achieved from a previous study. The IgG antibody purified from the antiserum of recombinant P10-immunized mice by protein A-agarose affinity chromatography could specifically detect both the target protein and SRBSDV at a dilution of 1:100000. In the trial test of SRBSDV diagnosis, the dot-ELISA assay using the obtained anti-SRBSDV antibody showed an accuracy rate of 90.9% in comparison with the standard RT-PCR assay. These results are important premises for the large-scale application of dot-ELISA assay for SRBSDV diagnosis in order to protect rice crops against viral disease damage.

Virus Southern rice black-striked dwarf virus (SRBSDV) disease caused serious damage rice growing areas in Northern and Central Vietnam over the past decade. While the application of SRBSDV diagnostic methods based on the Reverse transcription polymerase chain reaction (RT-PCR) technique was impossible due to technical complexity, simpler SRBSDV diagnostic techniques using specific antibody have not yet been developed in Vietnam. The biggest difficulty right now was the absence of commercial specific antibodies against SRBSDV. To develop diagnostic techniques by enzyme-linked immunosorbent assay (ELISA) for SRBSDV detection, in a previous study, we created antibodies against SRBSDV from the 66 kDa recombinant SRBSDV protein P10 expressed in E. coli; the obtained antibodies had a titer of 1:5000 dilution. Here, we continued to produce polyclonal antibodies against SRBSDV from small antigenic peptide (PASTTDVTHYGGY) derived from the P10 envelope protein, which was consevative in Vietnamese SRBSDV population. Titer of the purified IgG antibody was exmined using Dot enzyme-linked immunosorbent assay (Dot-ELISA) which showed a titer of 1:40000 dilution. The specific binding between anti-peptide IgG antibodies diluted at 1:40000 and the recombinant P10 protein in E. coli extraction was confirmed by using western blotting. In Dot-ELISA, our antibodies could distinguish between the SRBSDV-infected and non-infected rice samples. Our research results open up a new opportunity for developing the rapid diagnosis Southern rice black-striked dwarf virus membrane-type kit in Vietnam.

Background Mycobacterium tuberculosis strain diversity and drug resistance among people living with human immunodeficiency virus (HIV) in Vietnam have not been described previously. Methods We examined M. tuberculosis isolates from TB/HIV co-infected patients in Ho Chi Minh City, Vietnam. Drug susceptibility testing (DST), spoligotyping and 24-locus Mycobacterial Interspersed Repetitive Unit (MIRU-24 typing) were performed, and the rpoB, katG, inhA and inhA promoter, rpsL, rrs and embB genes were sequenced in all drug resistant isolates identified. Results In total, 84/200 (42.0%) strains demonstrated "any drug resistance"; 17 (8.5%) were multi-drug resistant (MDR). Streptomycin resistance was present in 80 (40.0%) isolates; 95.2% (80/84) with "any drug resistance" and 100% with MDR. No rifampicin monoresistance was detected. Of the rifampicin resistant strains 16/18 (88.9%) had mutations in the 81-bp Rifampicin Resistance Defining Region (RRDR) of the rpoB gene. Isoniazid resistance was mostly associated with Ser315Thr mutations in the katG gene (15/17; 88.2%). Beijing (49.0%) and East African Indian (EAI) lineage strains (35.0%; 56/70 EAI-5) were most common. Conclusion TB/HIV co-infection in Vietnam was associated with high rates of TB drug resistance, although we were unable to differentiate new from retreatment cases.

Background Improved and affordable diagnostic or triage tests are urgently needed at the microscopy centre level. Automated digital microscopy has the potential to overcome issues related to conventional microscopy, including training time requirement and inconsistencies in results interpretation. Methods For this blinded prospective study, sputum samples were collected from adults with presumptive pulmonary tuberculosis in Lima, Peru and Ho Chi Minh City, Vietnam. TBDx performance was evaluated as a stand-alone and as a triage test against conventional microscopy and Xpert, with culture as the reference standard. Xpert was used to confirm positive cases. Findings A total of 613 subjects were enrolled between October 2014 and March 2015, with 539 included in the final analysis. The sensitivity of TBDx was 62·2% (95% CI 56·6–67·4) and specificity was 90·7% (95% CI 85·9–94·2) compared to culture. The algorithm assessing TBDx as a triage test achieved a specificity of 100% while maintaining sensitivity. Interpretation While the diagnostic performance of TBDx did not reach the levels obtained by experienced microscopists in reference laboratories, it is conceivable that it would exceed the performance of less experienced microscopists. In the absence of highly sensitive and specific molecular tests at the microscopy centre level, TBDx in a triage-testing algorithm would optimize specificity and limit overall cost without compromising the number of patients receiving up-front drug susceptibility testing for rifampicin. However, the algorithm would miss over one third of patients compared to Xpert alone.

Influenza B viruses circulate throughout Viet Nam, and their activities vary by region. There have been two antigenically distinct lineages of influenza B viruses co-circulating in the past 20 years; however, only one lineage is selected as a component of contemporary trivalent seasonal influenza vaccines. To improve the understanding of circulating influenza B lineages and influenza vaccine mismatches, we report the virus lineages circulating in northern Viet Nam over an eight-year period (2007-2014).Lineages of 331 influenza B viruses were characterized by haemagglutination inhibition assay against standard reference ferret (Yamagata) and sheep (Victoria) antisera. Sequence analysis of the haemagglutinin gene was performed in 64 selected influenza B isolates.The proportion of influenza B lineages changed by year. The Yamagata lineage predominated in 2007, 2008 and 2012; the Victoria lineage predominated in 2009-2014 except 2012. The two lineages showed continuous evolution over time. The Northern Hemisphere's influenza vaccine components were mismatched with the predominant circulating viruses in 2007, 2009 and 2014.The seasonality of influenza B activity is more variable in tropical and subtropical regions than in temperate zones. Our data showed a common co-circulation of both influenza B lineages in northern Viet Nam, and it was difficult to predict which one was the predominant lineage. Quadrivalent influenza vaccines containing both lineages may improve the effectiveness of influenza vaccine programmes in the future.

Background The GeneXpertMTB/RIF (Xpert) assay is now recommended by WHO for diagnosis of tuberculosis (TB) in children but evaluation data is limited. Methods One hundred and fifty consecutive HIV negative children (

We investigated whether down-regulation of arginine decarboxylase (ADC) activity and concomitant changes in polyamine levels result in changes in the expression of downstream genes in the polyamine pathway. We generated transgenic rice (Oryza sativa L.) plants in which the rice adc gene was down-regulated by expression of its antisense oat (Avena sativa L.) ortholog. Plants expressed the oat mRNA adc transcript at different levels. The endogenous transcript was down-regulated in five out of eight plant lineages we studied in detail. Reduction in the steady-state rice adc mRNA levels resulted in a concomitant decrease in ADC activity. The putrescine and spermidine pool was significantly reduced in plants with lower ADC activity. Expression of the rice ornithine decarboxylase (odc), S-adenosylmethionine decarboxylase (samdc) and spermidine synthase (spd syn) transcripts was not affected. We demonstrate that even though levels of the key metabolites in the pathway were compromised, this did not influence steady-state transcription levels of the other genes involved in the pathway. Our results provide an insight into the different regulatory mechanisms that control gene expression in the polyamine biosynthetic pathway in plants by demonstrating that the endogenous pathway is uncoupled from manipulations that modulate polyamine levels by expression of orthologous transgenes.

We posed the question of whether steady-state levels of the higher polyamines spermidine and spermine in plants can be influenced by overexpression of a heterologous cDNA involved in the later steps of the pathway, in the absence of any further manipulation of the two synthases that are also involved in their biosynthesis. Transgenic rice (Oryza sativa) plants engineered with the heterologous Datura stramonium S-adenosylmethionine decarboxylase (samdc) cDNA exhibited accumulation of the transgene steady-state mRNA. Transgene expression did not affect expression of the orthologoussamdc gene. Significant increases in SAMDC activity translated to a direct increase in the level of spermidine, but not spermine, in leaves. Seeds recovered from a number of plants exhibited significant increases in spermidine and spermine levels. We demonstrate that overexpression of the D. stramonium samdc cDNA in transgenic rice is sufficient for accumulation of spermidine in leaves and spermidine and spermine in seeds. These findings suggest that increases in enzyme activity in one of the two components of the later parts of the pathway leading to the higher polyamines is sufficient to alter their levels mostly in seeds and, to some extent, in vegetative tissue such as leaves. Implications of our results on the design of rational approaches for the modulation of the polyamine pathway in plants are discussed in the general framework of metabolic pathway engineering.

Background To control multidrug resistant tuberculosis (MDR-TB), the drug susceptibility profile is needed to guide therapy. Classical drug susceptibility testing (DST) may take up to 2 to 4 months. The GenoType® MTBDRplus test is a commercially available line-probe assay that rapidly detects Mycobacterium tuberculosis (MTB) complex, as well as the most common mutations associated with rifampin and isoniazid resistance. We assessed sensitivity and specificity of the assay by using a geographically representative set of MTB isolates from the South of Vietnam. Methods We re-cultured 111 MTB isolates that were MDR, rifampin-resistant or pan-susceptible according to conventional DST and tested these with the GenoType® MTBDRplus test. Results By conventional DST, 55 strains were classified as MDR-TB, four strains were rifampicin mono-resistant and 52 strains were susceptible to all first-line drugs. The sensitivity of the GenoType® MTBDRplus was 93.1% for rifampicin, 92.6% for isoniazid and 88.9% for the combination of both; its specificity was 100%. The positive predictive value of the GenoType® MTBDRplus test for MDR-TB was 100% and the negative predictive value 90.3%. Conclusions We found a high specificity and positive predictive value of the GenoType® MTBDRplus test for MDR-TB which merits its use in the MDR-TB treatment program in Vietnam.