Distribution of Salmonella paratyphi A outer membrane protein X gene and immune-protective effect related to its recombinant expressed products / 中华流行病学杂志

Objective To determine the distribution and sequence conservation of outer membrane protein X (ompX) gene in Salmonella paratyphi A isolates as well as the immunogenicity and irnmono-protection of ompX gene products.Methods OmpX gene in Salmonella paratyphi A isolates was detected by PCR and the amplification products were sequenced after the T-A cloning process.OmpX gene product was expressed with E.coli expression system and the expressed rOmpX was extracted by Ni-NTA affinity chromatography.SDS-PAGE and Bio-Rad Gel Image Analyzer were applied to examine the expression and yield of rOmpX.Both antigenicity and immune-reactivity of rOmpX were detected by immune-diffusion test,ELISA and Western blot assay.The immuneprotective effect of rOmpX against infection of Salmonella paratyphi in mice was determined and the agglutinative titers of sera from rOmpX-immunized mice was measured by micro-Widal' s test.Results All the tested Salmonella paratyphi A isolates had ompX gene with high nucleotide or amino acid sequence identity (99.2％-100.0％ or 98.4％-100.0％).When rOmpX was induced to rabbits to produce high level antibody and combined with antiserum against whole cell of Salmonella paratyphi A,the results displayed a positive Western hybridization signal.Results from ELISA demonstrated that 95.6％ (65/68) of the serum samples from paratyphoid-A patients were positive on rOmpX antibody.Mice that were immunized with 100 μg or 200 μg rOmpX displayed an immune-protective rate of 93.3％ (14/15) or 100.0％ (15/15).Sera from those rOmpX-immunized mice provided 1 ∶ 10-1 ∶ 40 agglutination titers in both H antigens of Salmonella paratyphi A and Salmonella typhi.Conclusion The recombinant expression product of ompX gene could be used as a candidate antigen for developing genetic engineering vaccines against Salmonella paratyphi A infection.

Rapid detection of rpoB gene mutations in rif-resistant M. tuberculosis isolates by oligonucleotide microarray / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To detect the specific mutations in rpoB gene of Mycobacterium tuberculosis by oligonucleotide microarray.</p><p><b>METHODS</b>Four wild-type and 8 mutant probes were used to detect rifampin resistant strains. Target DNA of M. tuberculosis was amplified by PCR, hybridized and scanned. Direct sequencing was performed to verify the results of oligonucleotide microarray.</p><p><b>RESULTS</b>Of the 102 rifampin-resistant strains 98 (96.1%) had mutations in the rpoB genes.</p><p><b>CONCLUSION</b>Oligonucleotide microarray with mutation-specific probes is a reliable and useful tool for the rapid and accurate diagnosis of rifampin resistance in M. tuberculosis isolates.</p>

Establishment and application of enzyme linked immunosorbent assay based on the outer membrane pIA-pIB fusion gene of Neisseria gonorrhoeae / 中华流行病学杂志

<p><b>OBJECTIVE</b>To clone pIA and pIB genes of Neisseria gonorrhoeae,and to construct pIA-pIB fusion gene and its prokaryotic expression system, and to establish enzyme linked immunosorbent assay (ELISA) based on rPIA-PIB for detecting serum and pus samples from gonorrhea patients and to evaluate the sensitivity and specificity of the ELISA.</p><p><b>METHODS</b>pIA-pIB fusion gene was constructed by polymerase chain reaction (PCR) using linking primers and a prokaryotic expression system of the fusion gene was constructed by using routine molecular biological methods. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) plus BioRad Gel Image Analyzer was used to measure the expression of the target recombinant protein rPIA-PIB. Ni-NTA affinity chromatography was performed to extract and purify rPIA-PIB. An ELISA by using rPIA-PIB as the coated antigen for detecting the specific IgG against rPIA and/or rPIB in gonorrhea patients' sera as well as another ELISA by using rPIA-PIB antiserum as the first antibody for detecting the rPIA and/or rPIB in gonorrhea patients' pus samples were established. In these experiments, ELISAs associated with rPIA, rPIB and their antisera were applied as the controls.</p><p><b>RESULTS</b>100% similarities of the nucleotide and putative amino acid sequences of the pIA-pIB fusion gene were confirmed when compared with the original sequences. The output of rPIA-PIB was 29.8% of the total bacterial proteins. The purified rPIA-PIB only showed a single target protein segment in gel after SDS-PAGE. Using a positive rate (98.3%) of rPIA-PIB-IgG-ELISA to detect 119 cases of gonorrhea patients' serum samples was remarkably higher than that of rPIA-IgG-ELISA (30.3%) or rPIB-IgG-ELISA (66.4%) (P<0.01). The positive rate (91.6%) of rPIA-PIB-ELISA to detect 119 cases of gonorrhea patients' pus samples was also significantly higher than that of rPIA-IgG-ELISA (27.7%) or rPIB-IgG- ELISA (62.2%) (P<0.01).</p><p><b>CONCLUSION</b>In this study we successfully constructed pIA-pIB fusion gene of N. gonorrhoeae and its prokaryotic expression system while rPIA-PIB showed obvious superiority used as the antigen in gonorrhea associated detection kits compared to both the rPIA and rPIB.</p>