Molecular Identification and Evaluation of the Genetic Diversity of Dendrobium Species Collected in Southern Vietnam.

Dendrobium has been widely used not only as ornamental plants but also as food and medicines. The identification and evaluation of the genetic diversity of Dendrobium species support the conservation of genetic resources of endemic Dendrobium species. Uniquely identifying Dendrobium species used as medicines helps avoid misuse of medicinal herbs. However, it is challenging to identify Dendrobium species morphologically during their immature stage. Based on the DNA barcoding method, it is now possible to efficiently identify species in a shorter time. In this study, the genetic diversity of 76 Dendrobium samples from Southern Vietnam was investigated based on the ITS (Internal transcribed spacer), ITS2, matK (Maturase_K), rbcL (ribulose-bisphosphate carboxylase large subunit) and trnH-psbA (the internal space of the gene coding histidine transfer RNA (trnH) and gene coding protein D1, a polypeptide of the photosystem I reaction center (psaB)) regions. The ITS region was found to have the best identification potential. Nineteen out of 24 Dendrobium species were identified based on phylogenetic tree and Indel information of this region. Among these, seven identified species were used as medicinal herbs. The results of this research contributed to the conservation, propagation, and hybridization of indigenous Dendrobium species in Southern Vietnam.

The emergence of plasmid-borne cfr-mediated linezolid resistant-staphylococci in Vietnam.

OBJECTIVES: Linezolid is one of the last resort antibiotics effectively used in the treatment of infections caused by multidrug-resistant Gram-positive bacteria. Recent outbreaks of Linezolid resistance have been the great concern worldwide, while many countries have not experienced it. In this work, we aimed to evaluate the existence of linezolid resistance and further clarify potential resistance mechanism(s) in staphylococcal isolates obtained from the hospital in Vietnam, a country in which linezolid resistance had not been previously detected. METHODS: Seventy staphylococcal clinical isolates including MRSA (n=63) and methicillin-resistant coagulase-negative staphylococci (MRCNS, n=7) were collected and analyzed for linezolid resistance. Linezolid-resistant isolates were submitted for whole genome sequencing to search for the resistance determinants. RESULTS: We identified two coagulase-negative staphylococcal isolates that were resistant to linezolid. Whole genome sequencing revealed several alterations in the 23S rRNA and L3, L17, L22, L24, L30 ribosomal proteins. Importantly, both isolates harbour the chloramphenicol/florfenicol resistance (cfr) gene on a plasmid. The plasmid was closely identical to the pLRSA417 plasmid that was originally reported in China. CONCLUSIONS: To the best of our knowledge, this is the first report of cfr-mediated linezolid resistance in clinically isolated staphylococci in Vietnam. We suggest that adequate surveillance is necessary to monitor the dissemination of linezolid resistance among staphylococcal species and other important pathogens.

Characterization and thermal inactivation kinetics of highly thermostable ramie leaf ß-amylase.

We characterized ramie leaf ß-amylase, and determined its thermostability and kinetic parameters. The enzyme was purified 53-fold using ammonium sulfate fractionation (40-60% saturation), anion exchange chromatography on DEAE-cellulose and gel permeation chromatography on Superdex-200. The purified enzyme was identified as ß-amylase with molecular mass of 42kD. The enzyme displayed Km and kcat values for soluble potato starch of 1.1mg/mL and 7.8s-1, respectively. The enzyme had a temperature optimum of 65°C, and its activity at 70°C was 92% of that at the optimal temperature after a 15-min incubation. Furthermore, enzyme activity was stable during treatment at 55°C for 60min but was inactivated rapidly at >75°C. This thermal behavior indicates that ramie leaf ß-amylase has excellent intermediate temperature-stable enzyme properties for the baking and bio-industries. Inactivation of the enzyme followed first-order kinetics in the range of 55-80°C. The enthalpy change of thermal inactivation (ΔH‡), ΔG‡, and ΔS‡ were 237.2kJ/mol, 107.7kJ/mol, and 0.39kJ/molK at 333K, respectively. The D-value at 65°C (=110min) and the z-value (=9.4°C) are given for food processing.

Generation and characterization of soluble interleukin-33 receptor fused with immunoglobulin gamma-1 constant domain expressed by Pichia pastoris yeast.

OBJECTIVES: Interleukin (IL)-33 is a novel member of pro-inflammatory cytokine IL-1 family, which plays an important role in the immune response. IL-33 was proved to involve in many inflammatory and allergic diseases, thus the inhibition of this cytokine may be a promising treatment for these diseases. Arms of the study were to generate mouse soluble IL-33 receptor fused with human IgG1 Fc domain (msIL33R-Fc) expressed by Pichia pastoris yeast and to characterize the IL-33 inhibitory activity of this protein. METHODS: Clone of P. pastoris expressing msIL33R-Fc was established and the recombinant protein was harvested from culture supernatant by protein A sepharose beads. Recombinant msIL33R-Fc was analysed by SDS-PAGE and Western blotting and activity of the protein was investigated using the immunoprecipitation and the bio-assay on EL-4 cells. KEY FINDINGS: P. pastoris-derived msIL33R-Fc was expressed as a glyco-protein and perhaps in dimeric form. The glycosylation of protein expressed by P. pastoris yeast was more intensive and more heterogeneous compared with the counterpart protein expressed from HEK293 cells. Similar to HEK293-derived protein, msIL33R-Fc from P. pastoris was able to capture IL-33 and to interfere with the interaction between IL-33 and IL-33R in in-vitro condition. In IL-33-stimulated EL-4 cell bio-assay, P. pastoris-derived msIL33R-Fc suppressed IL-33 activity similarly as HEK293-derived msIL33R-Fc did. CONCLUSIONS: P. pastoris yeast can express and secrete bio-functional fusion protein sIL33R-Fc IgG1 and this expression system may be beneficial in future studies on the fusion protein.