Correlation between pulsed-field gel electrophoresis profiles and Salmonella serotypes / 中华流行病学杂志

Objective To analyze the relationship between pulsed-field gel electrophoresis (PFGE) subtyping and serotyping of Salmonella (S.).Methods PFGE was performed and profiles were analyzed on 1230 Salmonella isolates which comprising the top five serotypes including Typhimurium,Enteritidis,Derby,Agona and Senftenberg identified in China.The potential predictive relationship between PFGE banding patterns and particular serotypes was compared and the discriminatory consensus band class markers of individual serotypes were identified.Results Among all the 1230 Salmonella strains,1149 strains were found assistant with serotyping through PFGE cluster analysis,providing the matching accuracy reaching 93.4％.For the five serotypes,the positive prediction rate appeared more than 90.0％ and the negative prediction rate was over 95.0％ on serotype cluster prediction.Conclusion Results presented in this study were representatives of the top 5 Salmonella serovars,showing that PFGE cluster analysis could provide clues to identity and confirmation of serotypes.

The fundamental role of stage control technology on the detectability for Salmonella networking laboratory / 中华流行病学杂志

<p><b>OBJECTIVE</b>To evaluated the fundamental role of stage control technology (SCT) on the detectability for Salmonella networking laboratories.</p><p><b>METHODS</b>Appropriate Salmonella detection methods after key point control being evaluated, were establishment and optimized. Our training and evaluation networking laboratories participated in the World Health Organization-Global Salmonella Surveillance Project (WHO-GSS) and China-U.S. Collaborative Program on Emerging and Re-emerging infectious diseases Project (GFN) in Shanghai. Staff members from the Yunnan Yuxi city Center for Disease Control and Prevention were trained on Salmonella isolation from diarrhea specimens. Data on annual Salmonella positive rates was collected from the provincial-level monitoring sites to be part of the GSS and GFN projects from 2006 to 2012.</p><p><b>RESULTS</b>The methodology was designed based on the conventional detection procedure of Salmonella which involved the processes as enrichment, isolation, species identification and sero-typing. These methods were simultaneously used to satisfy the sensitivity requirements on non-typhoid Salmonella detection for networking laboratories. Public Health Laboratories in Shanghai had developed from 5 in 2006 to 9 in 2011, and Clinical laboratories from 8 to 22. Number of clinical isolates, including typhoid and non-typhoid Salmonella increased from 196 in 2006 to 1442 in 2011. The positive rate of Salmonella isolated from the clinical diarrhea cases was 2.4% in Yuxi county, in 2012. At present, three other provincial monitoring sites were using the SBG technique as selectivity enrichment broth for Salmonella isolation, with Shanghai having the most stable positive baseline.</p><p><b>CONCLUSION</b>The method of SCT was proved the premise of the network laboratory construction. Based on this, the improvement of precise phenotypic identification and molecular typing capabilities could reach the level equivalent to the national networking laboratory.</p>

Typhoid and paratyphoid fever in Yunnan province: distributional patterns and the related meteorological factors / 中华流行病学杂志

Objective To characterize the spatial distribution of typhoid and paratyphoid fever(TPF)in Yunnan province, China and to determine the effectiveness of meteorological factors on the epidemics of TPE Methods Data of reported TPF cases in Yunnan province(2001 -2007)from the China Information System for Diseases Control and Prevention was applied to GIS-based spatial analyses to detect their spatial distribution and clustering of TPF incidence at the county level.Panel data analysis was used to identify the relationships between the TPF incidence and meteorological factors including monthly average temperature, monthly cumulative precipitation and monthly average relative humidity. Results During the study period, the average incidence of TPF in Yunnan province was 23.11/100 000, with majority of the TPF cases emerged in summer and autumn. Although widely distributed, two TPF clusters were detected in Yunnan province based on the spatial analysis:one area around Yuxi city with the average annual incidence as 207.45/100 000 and another at the junctions of Yunnan province with Burma and Laos. Based on results from panel data analysis, the incidence of TFP was shown to be associated with meteorological factors such as temperature,precipitation, relative humidity and one month lag of temperature increase [10 ℃ increase in the monthly average temperature:IRR=1.30(95%CI: 1.24-1.36);10% increase in monthly average relative humidity:IRR= 1.07(95%CI: 1.05-1.09); 100 mm rise in monthly cumulative precipitation:IRR=1.02(95%CI: 1.00-1.03); and 10 ℃ average temperature increase, the last month: IRR=1.73(95%CI: 1.64-1.82)]. Conclusion Areas with high TPF incidence were detected in this study,which indicated the key areas for TPF control in Yunnan province. Meteorological factors such as temperature, precipitation and humidity played a role in the incidence of TPF.

Assessment of the application of variable-number tandem repeat loci of Salmonella Enteritidis in subtyping multiple-locus variable-number tandem repeat analysis / 中华预防医学杂志

<p><b>OBJECTIVE</b>To evaluate the feasibility of the application of variable-number tandem repeat (VNTR) loci of Salmonella Enteritidis (S. enteritidis) in subtyping mutiple-locus variable-number tandem repeat analysis (MLVA).</p><p><b>METHODS</b>A total of 16 isolates of S.enteritidis from different place and time in China were preliminarily assessed by choosing 11 reported VNTR loci, the loci with single amplified bands were picked to subtype all 104 S. enteritidis isolates. The isolates were also analyzed by pulse field gel electrophoresis (PFGE) to compare the superiority or inferiority of MLVA method and PFGE method.</p><p><b>RESULTS</b>Seven VNTR loci were selected from the preliminary screening to expand the analysis, and the 7 VNTR loci had grouped 104 of S.enteritidis isolates into either 16 MLVA subtypes or 22 PFGE subtypes, with the D value at 0.7222 and 0.7974, respectively. Comparing with the isolates in MLVA subtypes, the isolates in PFGE showed a stronger resolving power. Meanwhile the results in PFGE showed a more disperse frequency distribution than those in MLVA.</p><p><b>CONCLUSION</b>These results indicate that some VNTR locus which have shown a good polymorphism internationally, may fail to show polymorphism in China, thereby, more VNTR loci should be included in MLVA and the wide screening may benefit the unity of global laboratorial methods.</p>

Comparison of the transcriptional levels of mannitol PTS operon between epidemic and non-epidemic strains of Vibrio cholerae / 中国医学科学院学报

<p><b>OBJECTIVE</b>To compare the transcription difference of the mannitol PTS genes between epidemic and non-epidemic strains of Vibrio cholerae El Tor in mannitol ferment tests.</p><p><b>METHODS</b>Growth curves of 10 epidemic strains (slow-ferment) and 10 non-epidemic strains (rapid-ferment) of Vibrio cholerae were detected in the process of fermentation test, and the transcriptional level of mannitol PTS operon of these strains were determined with quantitative reverse-transcriptional PCR.</p><p><b>RESULTS</b>After 4 hours of test, the non-epidemic strains became positive and the average growth density of the non-epidemic strains was higher than that of the epidemic strains; however, some were still lower than the epidemic strains. In contrast, at the eighth hour of test, when epidemic strains got positive, they showed higher average growth density. Compared to the epidemic strains, the transcription of mannitol PTS genes of the non-epidemic strains were much more active at the 1st and 2nd hour and were lower at the 4th and 8th hour.</p><p><b>CONCLUSIONS</b>The difference of mannitol PTS operon transcription level should be an important feature to identify the epidemic and non-epidemic strains of Vibrio cholerae, which directly influences the mannitol fermentation rate during the test. The growth rate is not a key factor that affect such difference.</p>

Development and application of real-time polymerase chain reaction to detect Vibrio cholerae O1 and O139 in river water / 中华流行病学杂志

<p><b>OBJECTIVE</b>To develop a real-time SYBR Green polymerase chain reaction (PCR) for detection of Vibrio cholerae serogroups O1 and O139, and to evaluate its reliability through detection of estuary water samples.</p><p><b>METHODS</b>O antigen rfb genes specific for O1 and O139 were used for the design of PCR primers. The real-time SYBR Green PCR system in detecting O1 and O139 specific rfb genes in one tube was developed, and its sensitivity, specificity and reproducibility were evaluated. The ability of the real-time PCR in detection of estuary water samples was compared with the routine PCR and bacteria isolation.</p><p><b>RESULTS</b>The amplification of O1 or O139 specific target gene could be detected according to the melt curve temperature of amplicons. No amplification was observed in the templates of other 10 non-cholerae vibrios. When comparing to the real-time PCR to bacteria isolation in detection of 524 estuary water samples, it showed high sensitivity, plus also positive in real-time PCR detection among all the samples in which bacteria of O1 or O139 were isolated.</p><p><b>CONCLUSION</b>The real-time SYBR Green PCR could be used as the first step of rapid environment screen of V. cholerae in water samples thus might enhance the efficiency of isolation in screening of large amount of water samples.</p>

Surveillance on severe acute respiratory syndrome associated coronavirus in animals at a live animal market of Guangzhou in 2004 / 中华流行病学杂志

<p><b>OBJECTIVE</b>To study the prevalence of severe acute respiratory syndrome coronavirus (SARS-CoV) like virus in animals at a live animal market of Guanzhou in 2004 before and after culling of wild animal action taken by the local authority, in order to predict the re-emerging of SARS from animal originals in this region.</p><p><b>METHODS</b>Animals at live animal market were sampled for rectal and throat swabs in triplicate. A single step realtime reverse transcription-polymerase chain reaction (RT-PCR) diagnostic kit was performed for screening SARS-CoV like virus, the manual nested RT- PCR and DNA sequencing were performed for confirmation. Only specimens which tested positive for both of the N and P genes by nested RT-PCR were scored as positive.</p><p><b>RESULTS</b>In 31 animals sampled in January 5 2004 before culling of wild animals at Guangdong Province, including 20 cats (Felis catus), 5 red fox (Vulpes vulpes) and 6 Lesser rice field rats (Rattus losea), 8 (25.8%) animals were tested positive for SARS-CoV like virus by RT-PCR methods, of which 4 cats, 3 red fox and one Lesser rice field rats were included. However, two weeks after culling of animals and disinfection of the market were implemented, in 119 animals sampled in January 20 2004, including 6 rabbits (Oryctolagus cuniculus), 13 cats, 46 red jungle fowl (Gallus gallus), 13 spotbill duck (Anas platyrhynchos), 10 greylag goose (Anser anser), 31 Chinese francolin (Franclinus pintadeanus), only rectal swab from one greylag goose was tested positive for SARS-CoV like virus. Furthermore, in 102 animals that including 14 greylag gooses, 3 cats, 5 rabbits, 9 spotbill duck (Anaspoecilorhyncha), 2 Chinese francolin (Franclinus pintadeanus), 8 common pheasant (Phasianus colchicus), 6 pigeons, 9 Chinese muntjac (Muntiacus reevesi), 19 wild boar (Sus scrofa), 16 Lesser rice field rats, 5 dogs, 1 mink (Mustela vison), 3 goats, 2 green peafowl (Pavo muticus) sampled in April, May, June, July, August and November, only rectal swab from one pig was tested positive. However, of 12 and 10 palm civets sampled in November and December including five of which had been at the live animals market for 2 days, none of them was tested positive.</p><p><b>CONCLUSION</b>This findings revealed that animals being sampled in April, May, June, July, August and November of 2004, only one rectal swab from a pig was tested positive as SARS-CoV like virus, much lower than the results from the previous year, suggesting that the possibility of re-emerging of human infection from animal origins is low for the winter of 2004-2005.</p>