Assessment and application of a molecular diagnostic method on the detection of four types of diarrheagenic Escherichia coli / 中华流行病学杂志

<p><b>OBJECTIVE</b>To establish and evaluate a molecular diagnostic method for routine monitoring of four types of diarrheagenic Escherichia (E.) coli (DEC)and to study the distribution of four types of DEC isolated from diarrheal patients in Shanghai.</p><p><b>METHODS</b>DEC-PCR standard operation procedure(SOP)had been developed for DEC detection and isolation, using the Statens Serum Institute (SSI) DEC PCR kits with multiplex PCR technique after verification tests on reference strains. Diarrhea specimens from 3 clinical hospitals in Shanghai were tested from June to September, 2012.</p><p><b>RESULTS</b>Specificity of the PCR kit was 100% by verification on the 26 DEC reference strains. A total number of 218 DEC isolates, including 181 fermented lactose and 37 unfermented lactose were identified from the 1887 stool specimens of diarrhea patients, with positive rate as 11.6%. The most common pathogen(54.1%, 118/218)was enteropathogenic E. coli(EPEC), followed by enterotoxigenic E. coli(ETEC, 41.3%, 90/218), enteroinvasive E. coli (EIEC, 4.1%, 9/ 218) and Shigatoxin-producing E. coli(STEC, 0.5%, 1/218)in addition to 18 Shigella isolates. ETEC dominated in diarrhea patients with foreign residency, as well as 1/3 were perinatal stage of neonatal ETEC of all diarrhea cases under the age of 5, while EPEC dominated in the Chinese diarrhea patients especially among young kids under the age of 2.</p><p><b>CONCLUSION</b>Data was reliable after assessment on this molecular diagnostics and seperation procedures used for the routine monitoring on four types of DEC, while the diagnosis and reference ability of DEC regarding the laboratories net-working on food-borne pathogens need to be built up and improved.</p>

Gold-immunochromatography assay for detection of Yersinia pestis F1 antigen / 中国地方病学杂志

Objective To study the sensitivity and specificity of gold-immunochromatography assay (GICA) for detection of Yersiniapestis(Y. pestis ) F1 antigen. Methods Viscera organ(liver and spleen) specimens of 308 mice with virulent Y. pestis infection and 225 control specimens of rats(217 Spermophilus dauricus, 5 mice,3 guinea pigs) were detected by GICA dipstick with monoclonal antibody against plague F1 antigen (F1MAb).Meanwhile, micro-method of reverse indirect hemagglutination assay(RIHA) and bacteria culture were carried out for parallel testing. Results Bacteriological examination of 225 control specimens, and F1 antigen detected with GICA and RIHA were all negative. No cross-reaction with related Yersinia pseudotuberculosis at 1 x 108 cfu/ml level was found in GICA and RIHA. Detection sensitivity of Y. pestis by GICA and RIHA were 2.5 × 105 cfu/ml and 2.0 × 105 cfu/ml, respectively, and of F1 antigen were 1μg/L and 10 μg/L, respectively. Coincidence was 97.94% (522/533) between GICA and bacteriological test, Kappa = 0.959, and the difference was statistically insignificant(x2 = 0.36, P ＞ 0.05); and 97.94%(522/533) between GICA and RIHA, Kappa = 0.959, with statistically significant difference in the positive detection rates(x2 = 9.09, P ＜ 0.05). Out of the 308 infected mice, 284 were positive of plague bacterial cultured, In 284 samples with positive bacterial culture, there were 280 of positive detected by GICA for F1 antigen, positive rate of F1 antigen was 98.59%, higher than that by RIHA[the positive rate of 96.13%(522/533)], with statistically significant difference(x2 = 5.14, P ＜ 0.05). Sensitivity of GICA was 98.59% (280/284), specificity was 97.19% (242/249), positive predictive value (PPV) was 97.56% (280/287),negative predictive value ( NPV ) was 98.37% (242/246), and Youden index was 0.9578. Conclusions GICA is sensitive and specific, fast and simple in detection of F1 antigen of the plague. It's a valuable detection technique for early and rapid diagnosis of plague.

Study on immunization of Balb/c mice with F1 antigen of Yersinia pestis / 中国地方病学杂志

Objective To study the doses and methods of F1 antigen(F1Ag) to immune Balb/c mice during the establishment of hybridoma cell strains. Secreting McAbs against F1Ag of Yersinia pestis. Methods Balb/c mice of seven to nine weeks old were randomly divided into six groups. The first four groups were 150, 100, 50 and 25 μg F1Ag inoculated group, having multipoint hypodermic inoculation of F1Ag of 150, 100, 50 and 25 μg followed by multipoint hypodermic inoculation of F1Ag of 100 μg for a second time and then intraperitoneal injection of 100 μg. Next, hypodermically inoculated group received F1Ag of 100 μg for three times in multiple points. Finally, the intraperitoneal injection group was intraperitoneally inoculated with F1Ag of 100 μg for three times. Emulsification liquid of F1Ag + Complete Frednd's adjuvant(CFA) of equivalence was used in the first inoculation, emulsification liquid of F1Ag + Incomplete Frednd's adjuvant(IFA) balanced mix in the second, F1Ag liquid in the third. One week afterwards, tail blood of the mice was collected to test antibody titers of anti-F1Ag by double antigens sandwich enzyme linked immunosorbent assay (DAgS-ELISA) and trace indirect hemagglutination assay(IHA). Results The levels of antibody of anti-F1Ag in 150,100,50 and 25 μg groups had statistics difference (DAgS-ELISA method: G = 12 173.87,13 440.37,15 024.19 and 4466.72, F= 3.11, P< 0.05;IHA: G = 19 972.32,18 089.40,23 170.47 and 4871.08, F = 4.11, P < 0.05). Immune effect of the 3 groups of 150, 100 and 50 μg was almost the same (P> 0.05), and excelled as compared with that in 25 μg group with statistics difference(DAgS-ELISA method: t = 2.18,2.39,2.73, P < 0.05;IHA: t = 2.54,2.73,3.13, P< 0.05). The titer of F1 antibody had an increasing trend from the 100 μg group to hypodermic group and intraperitoneal injection groups, but without statistics difference (DAgS-ELISA method: G = 8933.44, 9986.16, 13 440.37;IHA: G = 13 777.25,16 384.00, 18 089.40, F = 0.66,0.25, all P > 0.05). Conclusions Hyodermical inoculation of F1Ag with the first dose of 50 μg in multiple points for mouse is appropriate, and a strengthening dose of 100 μg in an intraperitoneal injection may shorten the immune period.

Estimating rapid detection of F1 antigen of Yersinia pestis with gold-immunochromatography / 中国地方病学杂志

Objective To develop a rapid test for the detection of F1 antigen of Yersinia Pestis based on gold-immunochromatography.Methods F1 antibodies were coupled with colloidal gold to prepare collidal gold reagent,which was used to detect F1 antibodies based on double antigen sandwich.The collidal gold reagent was estimated for its sensitivity specificity and stablity in labs and 1798 samples were detected in 17 surveillance spots.Results The reagent was sensitive to 0.0010 g/L F1 antigens.The reagens kept stable when it had been placed at 4℃ or room-temperature for 12 months and did not react to Yersinia pseudotuberculosis and Yersinia enterolitica.In 17 surveillance labs the reagent was used to test 1798 viscera samples from animal.resulting an accordance rate of 97.11%(1746/1798)to bacterial culture and 96.83%(1741/1798)accordance to reverse indirect hemagglutination assay(RIHA),showing a higher detection rate[9.23%(166/1798)]compared with RIHA[6.79%(122/1798)]and bacterial culture[6.28%(113/1798)].Conclusions The collidal gold reagent,sensitive and specific in diagnosing Yersinia pestis infection of both human and animals,is a rapid method in surveillance spot.

Study on the application and evaluation of methods for gene and antigen detection in plague surveillance program / 中华流行病学杂志

<p><b>OBJECTIVE</b>To apply and evaluate new methods regarding specific gene and antigen detection in plague surveillance program.</p><p><b>METHODS</b>1798 samples from natural foci of plague were tested, using internal quality control multiple-polymerase chain reaction, F1 antigen marked by immuno chromatographic assay and enzyme linked immunosorbent assay. Culture of Yersinia pestis and reverse indirect hemagglutination assay were used as reference diagnostic methods.</p><p><b>RESULTS</b>The overall positive rate of culture on Yersinia pestis together with gene and antigen detection was 7.34%, showing an 16.81% increase when comparing to 6.28% using Yersinia pestis culture method alone. The rate of coincidence was 97.13%.</p><p><b>CONCLUSION</b>The new standard being used for specific gene and antigen detection could increase the positive rate of diagnosis on plague.</p>

Molecular biological characteristics and genetic significance of Yersinia pestis in China / 中华流行病学杂志

<p><b>OBJECTIVE</b>To understand the molecular biological characteristics in order to analyse the genetic background of Yersinia pestis in China.</p><p><b>METHODS</b>Primary datum on ribotyping, pulsed field gene electrophoresis (PFGE), random amplified polymorphic DNA (RAPD) and insertion sequence (IS) of Yersinia pestis were used and under cluster analysis. Genetic interval and various methods of recognized molecular feature between different strains were evaluated.</p><p><b>RESULTS</b>Ribotypes the PFGE types seemed to be corresponding. Stains from Microtus fuscus and area in Tibet Zhongba belonged to 7 copy rRNA gene and the genetic interval were the far more with 6 copy rRNA gene stains, and not definite with RAPD, but with many exceptions. The genetic interval between strains were showed by resemble value.</p><p><b>CONCLUSION</b>Yersinia pestis in China had its own manifold, particular molecular biological characteristics due to natural barriers, geographical complex, circumstances in Tianshan Mountains and Gandise Mountains areas. Yersinia pestis were limited to separateness, evoluted only in certain areas to form a great many gene types.</p>

Genetic analysis of Yersinia pestis strains isolated in China / 中华流行病学杂志

<p><b>OBJECTIVE</b>The strains of Yersinia pestis isolated in different period and different natural foci in China were analyzed.</p><p><b>METHODS</b>Traditional and molecular biological methods were used. Rhamnose fermentation, rRNA gene copy number, nitrite reduction, and the glycerol fermentation were important characters for typing, and pulse field gel electrophoresis (PFGE) and random amplified polymorphic DNA (RAPD) profile could reflect the genetic distance between the strains.</p><p><b>RESULTS</b>The strains could be divided into 15 genetic types by those 6 characters with each of them covered an isolated geographical territories.</p><p><b>CONCLUSION</b>The characters of strains were described; the genetic relationship of different types, their evolution, and the forming and shift of plague natural foci were analyzed.</p>

Application of Internal Amplification Control in the PCR Detection Method for Food-borne Salmonella / 微生物学通报

An internal amplification control, which could be co-amplified with the invA target gene of Salmonella in the PCR system, was constructed in order to indicate possible PCR inhibitors derived from food samples. Specificity of this PCR system was tested with 9 Salmonella strains and 15 non-Salmonella strains, and the results showed that there was a 374 bp amplicon resulted from all Salmonella strains, while only a 513 bp IAC amplicon appeared after the amplification for all non-Salmonella strains. The detection sensitivity of this PCR system was 12.8 fg/?L for purified target DNA, and the detection limit for artificially inoculated milks was 8 cfu /25g if they were enriched for 8h in buffered peptone water. Salmonella in 80 samples of seriously contaminated milks was detected by the PCR method developed in this study, and the experiments demonstrated that it could successfully eliminate false-negative results.