Establishment of an assay for identifying mutation of clarithromycin -resistance gene of Helicobacter pylori by real time PCR with a novel fluorescence quencher / 预防医学

Objective To establish a real time PCR assay with a novel fluorescence quencher for identification of mutation of clarithromycin -resistance gene of Helicobacter pylori.Methods Two mutations of 23S rDNA gene in Helicobacter pylori,No.2142 and 2143,were chosen as targets for detection,and then the primers and the probe with a novel fluorescence quencher were designed.The genome DNA of Helicobacter pylori was extracted,and then detected by real time PCR reported here.Meanwhile,the specificity,reproducibility and sensitivity of the assay were evaluated.Finally,the real time PCR described here,the real time PCR based on TaqMan,and a sequencing assay were applied to detect 55 Helicobacter pylori strains isolated from clinical specimens,respectively.The results from three assays were compared with each other in order to further evaluate the applicability of this assay in clinic.Results It indicated that the mutation points related to clarithromycin -resistance,A2142G and A2143G,were identified by real time PCR with a novel fluorescence quencher rapidly and accurately.Moreover the coefficient of variation was less than 5%.The limit of detection was 100 copies/reaction.While this assay was applied directly to detect 55 Helicobacter pylori strains,the results were in accordance with those obtained from a TaqMan real time PCR and a sequencing assay,respectively.Conclusion The real time PCR described here was a simple,reliable and accurate approach and substituted for the TaqMan real time PCR for identification of two mutation points of clarithromycin -resistance,A2142G and A2143G in Helicobacter pylori.Thus,a novel tool for diagnosis of gene mutation was provided and the results might be regarded as a substantial evidence for clinical individual therapy.

Development of multiplex real time PCR methodology for better identification and discrimination of Vibrio cholerae and O139 serotype / 中华流行病学杂志

Objective To develop a rapid, sensitive and specific assay method, based on multiplex real time PCR for identifying Vibrio cholerae and distinguishing Vibrio cholerae O139 serotype from Vibrio cholerae. Methods Cholera toxin A subunit gene (ctxA) and glycosyltransferase gene (LPSgt) were chosen as targets according to Vibrio cholerae and Vibrio cholerae O139 serotype,and then the primers and TaqMan-MGB probe were designed. The 5'end of probes was labeled with FAM and VIC fluoresceins respectively while the 3' end of probes was labeled with MGB. The PCR reaction was optimized systematically. Then the specificity, sensitivity and reproducibility of multiplex real time PCR were estimated. Finally, multiplex real time PCR was applied to detect the clinical specimens. Results Vibrio cholerae was identified by multiplex real time PCR accurately and quickly,which could distinguish Vibrio cholerae O139 serotype from Vibrio cholerae. Vibrio cholerae was identified positive for primer pairs and probes from ctxA gene, and Vibrio cholerae O139 serotype tested was positive for LPSgt gene. Meanwhile, none of other bacteria was identified. Sensitivity of the test was 2 × 102 cfu/ml. When this assay was applied directly to identify 45 clinical specimens, results showed that 10 were positive to Vibrio cholerae, in which 4 clinical specimens were positive to Vibrio cholerae O139 serotype. All the results were the same to the one that had been obtained from the conventional assays. Conclusion Our rsults showed that the multiplex real time PCR was a reliable,accurate and feasible method for identifying Vibrio cholerae that carrying toxin gene and distinguishing Vibrio cholerae O139 serotype from Vibrio cholerae. This method could be applied to the cholera surveillance, prevention and control system for identifying and distinguishing Vibrio cholerae in the labs.

Detection of co-infection with Lyme spirochetes and Spotted fever group rickettsiae in a group of Haemaphysalis longicornis / 中华流行病学杂志

Objective The present study was conducted to investigate the infection of Lyme disease, Spotted fever, Ehrlichiosis (anaplasmosisin) in wild animals and ticks in the mountain areas of Zhejiang province. Methods Nested polymerase chain reaction was used to amplify specific DNA sequences of Lyme spirochetes, Spotted fever group rickettsiae, Ehrlichia (anaplasma) from samples of mice and ticks. Results 14 positive samples were identified from 121 mice and 105 groups of ticks. Among mice samples, one positive 5S-23S rDNA intergenic spacer of Borreia burgdorferi and two 5' fragments of Ehrlichia (anaplasma) 16S rDNA were obtained. 11 positive results were detected from tick samples including three 5S-23S rDNA intergenic spacer regions of Borreia burgdorferi and eight 5' fragments of Spotted fever group rickettsiae outer member protein A gene. One group of adult ticks, Haemaphysalis longicornis, which had been collected from eastern mountain area were detected to have co-infected with Lyme spirochetes and Spotted fever group rickettsiae. The positive sequences of 5S-23S rDNA intergenic spacer and ompA gene were tested and analyzed as Lyme spirochetes while rickettsia which was closely related to Borrelia valaisiana and R. massilliae. Conclusion This was the first report about co-infection of Lyme spirochetes and Spotted fever group rickettsiae found in the same group of adult Haemaphysalis longicornis. It is very important to strengthen the surveillance program on tick-borne infectious disease and their pathogenic in vectors, wild animals and targeted high risk groups and to differentiate the clinical manifestation and diagnosis to extend the knowledge of tick-borne infectious diseases in Zhejiang.

Investigation on vibrio cholera carried in aquatic products of littoral areas, Zhejiang Province / 中华预防医学杂志

<p><b>OBJECTIVE</b>To examine vibrio cholera (V.C) in aquatic products of littoral area, Zhejiang Province and to provide scientific evidence for administration of aquatic products and cholera epidemic control.</p><p><b>METHODS</b>All 990 samples of aquatic products collected from local markets, eateries and aquafarms in three chosen areas. Samples were proliferated in alkaline liquid medium, and purified in NO: 4 medium, the isolations were identified biochemically, and phenotype of strains were defined by phagocyte and coagulation with V.C. diagnostic serum. Three virulence genes (ctx, ace, zct) of the isolated strains were detected by polymerase chain reaction (PCR).</p><p><b>RESULTS</b>There were 1.41% samples caught by V.C., having a carrying rate highest in turtles of 8.9%. 14 strains were defined as three serogroups, and the numbers of Inaba, Ogawa, and Hikojima types were 2, 2, 10 respectively. Virulence genes had detected in 9 of 12 stains. All genes were detected in 5 strains, only ZOT genes in 3 strains, and both CTX and ACE genes in 1 strain.</p><p><b>CONCLUSIONS</b>Aquatic products from inshore in Zhejiang Province caught with V.C. strains might be divided into three serogroups. Most of them should be virulence genes. Cholera epidemic outbreak might be caused by those contaminated products.</p>