上海市16个冷却塔水中军团菌脉冲场凝胶电泳分型及基因型监测

Objective To investigate the genotypic characteristics and persistence of Legionella pulsed-field gel electrophoresis (PFGE) patterns in 16 air-conditioner cooling towers in six different public sites of Shanghai. Methods From May to October, continuous sampling was operated once per month in 2007. Legionella strains isolated from the 16 cooling towers were confirmed by serological and latex agglutination. PFGE was applied for the fingerprinting of the isolates, while the culster results of PFGE were analyzed by BioNumerics software. Results 131 strains of Legionella were isolated, including L. pneumophila, L. bozemanae, L. micdadei and L anisa.52 distinguishable PFGE patterns were differentiated among the 16 cooling towers, with 37 patterns were owned by just one cooling tower, which was not shared with other cooling towers, while 15 patterns were shared by more than 2 cooling towers. All the cooling towers had ≥2 PFGE patterns,while in 13 cooling towers the same PFGE patterns were recovered during the six months. From June to October of 2007, 18 strains of Legionella belonging to the PFGE pattern of LPAs. SH0078 were isolated continuously from 6 cooling towers. Conclusion This study demonstrated great genotypic diversity and complexity of Legionella in cooling towers. Persistence of the PFGE patterns was observed in 81.25% of the cooling towers. The PFGE pattern of LPAs. SH0078 was distributed widely,suggesting it might be the dominate strain in Shanghai.     

中国嗜肺军团菌分离株脉冲场凝胶电泳分型分析以及数据库的建立

目的 对分离的262株嗜肺军团菌进行脉冲场凝胶电泳(PFGE)分析,初步建立中国嗜肺军团菌的PFGE分型数据库.方法 采用PFGE技术,对2004-2009年中国11个省(市)分离的嗜肺军团菌用AscⅠ酶切,BioNumerics软件分析PFGE图谱,并建立分子分型数据库.结果 262株嗜肺军团菌的PFGE图谱共分为108种不同的PFGE带型,相似性系数在16%～100%之间,通过聚类分析,可以分为差异明显的不同簇.不同省份、年份和血清型的菌株之间有交叉带型.结论 中国环境分离的嗜肺军团菌菌株基因组变异较大,同时也具有克隆化特征,且可能有多个克隆系存在.

Abstract：

Objective To analyze the molecular types of Legionella (L.) pneumophila strains isolated in China,and to develop the PulseNet-China Database of L.pneumophila.Methods Pulsed field gel electrophoresis (PFGE) was used to analyze 262 L.pneumophila strains collected from 11 provinces between 2004 and 2009 in China.Different kinds of genomic DNA in different L.pneumophila strains were isolated and separated after digesting with Asc Ⅰ.BioNumerics software was used to analysis the PFGE fingerprints.Results L.pneumophila strains isolated in China were quite different regarding their PFGE patterns.There were 108 PFGE types among the 262 strains tested in this study.The similarity value of these strains was in the range of 16%-100% and the same types were discovered in different provinces and years.Conclusion L.pneumophila strains isolated in China were with high genetic variations.There might be different clones existed in China.The development of PulseNet China Database was thus of great significance in monitoring the L.pneumophila strains in the future.     

军团菌rcp毒力基因的聚合酶链反应检测方法研究

目的 建立军团菌rcp毒力基因聚合酶链反应(PCR)检测方法.方法 根据GenBanK公布的嗜肺军团菌核苷酸序列合成军团菌rcp毒力基因的特异引物,采用PCR方法对2005年-2007年天津市中央空调冷却塔分离的16株嗜肺军团菌、杜氏军团菌(Legionella dumoffii,L.dum)、博氏军团菌(Legionella bozemanii,L.boz)、长滩军团菌(Legionellafeeleii,L.fee)等菌株进行了军团菌毒力基因rcp的检测.结果 3株嗜肺军团菌扩增出了900 bp的rcp基因片段,其余菌株未扩增出该基因片段.结论 本研究建立的军团菌毒力基因rcp的PCR检测方法具有较高的特异性和敏感性,适于军团菌毒力基因的深入研究.

Abstract：

Objective To establish a polymerase chain reaction method for the detection of the rcp virulence gene of L. pneumophila. Methods Sixteen strains of Legionella pneumophila, L. dumiffii, L. bozemanii and L. Longbeachae isolated from the cooling towers of the centralized air-conditioning systems in Tianjin form 2005 to 2007 were detected by polymerase chain reaction method using L. pneumophila rcp virulence gene-specific primer according to GenBank published nucleotide sequence. Results The 900 bp rcp genetic fragment was amplified in three strains of L. pneumophila, while others not. Conclusion The rcp virulence gene-based polymerase chain reaction method for the detection of L. pneumophila has been successfully established and is the foundation for the studies of Legionella virulence.     

肺炎克雷伯菌脉冲场凝胶电泳及多位点序列分型技术的联合应用

Objective To type Klebsiella pneumonia through methods including pulse-field gel electrophoresis (PFGE) in combination with multilocus sequence typing. Methods Four selected different Eps, referring to the Standard Operating Procedure of PulseNet China, were used. The single colony of Klebsiella pneumonia was quantified after enriched culture. Embedding organisms in agarose and genome DNA were lysed with Proteinase K and then digested by restriction endonuclease Xba Ⅰ , to produce agarose gel. Fingerprint was obtained through PFGE and bands were marked with their molecular weights and then analyzed by BioNumerics software. Using MLST to analyze the strains that were highly similar, by PFGE typing Results By comparing the four results from each Eps, fk3 (switch time from 6s to 36s,total run time is 18.5 hours) seemed to be better than the others.59 strains of Klebsiella pneumonia were divided into 47 PFGE types and 19 PFGE clusters. The highly similar strains could be typed into ST-340、ST-342、ST-343、ST-344、ST-345 by MLST. Among them, ST-342、 ST-343、 ST-344、 ST-345 types were all new MLST types that were reported in China.Conclusion Highly similar Klebsiella pneumonias typed by PFGE could also be typed by MLST.     

肺炎克雷伯菌脉冲场凝胶电泳及多位点序列分型技术的联合应用

Objective To type Klebsiella pneumonia through methods including pulse-field gel electrophoresis (PFGE) in combination with multilocus sequence typing. Methods Four selected different Eps, referring to the Standard Operating Procedure of PulseNet China, were used. The single colony of Klebsiella pneumonia was quantified after enriched culture. Embedding organisms in agarose and genome DNA were lysed with Proteinase K and then digested by restriction endonuclease Xba Ⅰ , to produce agarose gel. Fingerprint was obtained through PFGE and bands were marked with their molecular weights and then analyzed by BioNumerics software. Using MLST to analyze the strains that were highly similar, by PFGE typing Results By comparing the four results from each Eps, fk3 (switch time from 6s to 36s,total run time is 18.5 hours) seemed to be better than the others.59 strains of Klebsiella pneumonia were divided into 47 PFGE types and 19 PFGE clusters. The highly similar strains could be typed into ST-340、ST-342、ST-343、ST-344、ST-345 by MLST. Among them, ST-342、 ST-343、 ST-344、 ST-345 types were all new MLST types that were reported in China.Conclusion Highly similar Klebsiella pneumonias typed by PFGE could also be typed by MLST.     

福建省沿海地区鼠形动物巴尔通体感染状况调查及基因类型研究

Objective To investigate Bartonella infection in rodent hosts from different environments and types of climate in Fujian coastal regions. Genetypes of the Bartonella strains was also studied to provide scientific basis for prevention and control of the correlated diseases. Methods By random sampling method, we selected six study sites in Fujian southeastern coastal regions. Rodents were captured by cages to Isolate Bartonella strains. Bartonella-like isolates were confirmed by polymerase chain reaction (PCR). The 379 bp fragment of gltA gene was sequenced and the growth and development tree was constructed to determine Bartonella species. Distribution of Bartonella species in the different area and related hosts was also analysed. Results Bartonella species were isolated from 188 of 1161 small animals including five rodent species. The infected animals were grouped into 2 genera and 2 orders. They were Suncus murinus, Rattas norvegicus, Rnttus flavipectus, Mus masculus and Rattus rattus. The overall prevalence of Bartonella bacteremia was 16.19% in the most prevalent species of rodents in Fujian southeastern coastal regions including 21.43% in Suncus murinus, 13.54% in Rattas norvegicus and 18.27% in Rattus flavipectus. Rodents in every investigated areas were infected by Bartonella species (9.25% in Ningde, 9.52% in Fuzhou, 9.38% in Putian, 28.18% in Quanzhou, 17.42% in Xiamen and 13.33% in Zhangzhou). There were significant differences among infected rates in different annual accumulated temperature districts (χ2=12.93, P<0.001). Isolates from rodents were clustered in three genotypes (B.elizabethae, B.qeenslandensis and B.tribocorum A, B). Conclusion The local rodents in Fujian southeastern coastal regions were widely infected by Bartonella spp. Differences among the prevalent species of Bartonella in Fujian southeastern coastal region, Yunan and Beijing were noticed. Our findings suggested there was a need to study the prevalence, related vectors and the molecular organism of Bartonella spp.     

云南省2007--2009年流行性腮腺炎病毒SH和HN基因的遗传特征分析

目的 分析2007-2009年云南省腮腺炎病毒(MuV)分离株的SH和HN遗传特征.方法 采用反转录-聚合酶链反应从Vero细胞分离的病毒株基因组中扩增出SH基因和HN基因,测序后用Mega4.1软件分析其遗传特征.结果 云南省分离14株MuV的SH基因其核苷酸和氨基酸同源性为98.3%～100.0%和96.5%～100.0%,与其他省份比较其同源性为92.6%～99.4%和87.7%～100.0%,其中Wsh1和Wsh2与其他F基因型差异较大;与疫苗株同源性为84.5%～85.1%和77.2%;与其他基因型同源性为83.4%～90.9%和70.1%～86.0%.6株MuV分离株的HN基因与核苷酸和氨基酸同源性分别为99.3%～99.5%和99.1%～99.7%;与中国分离株SP株的核苷酸和氨基酸同源性均为99.8%;与其他基因型同源性为94.7%～96.8%和95.5%～99.1%;与疫苗株的同源性为92.4%～93.2%和95.5%～96.4%.结论 2007-2009年云南省流行的MuV均为F基因型;其HN基因比SH基因保守.

Abstract：

Objective To analyze genetic characterization of the small hydrophobic and hemagglutinin-neuraminidase genes of mumps virus(MuV)isolated in Yunnan province,China from 2007 to 2009.Methods Fourteen MuV strains were isolated in Yunnan,China from 2007 to 2009.Using RT-PCR,the SH gene fragments contained 316 nucleotides in all strains and HN gene of six strains were sequenced.The sequences were aligned with other mumps virus sequences downloaded from GenBank using Mega 4.1 software.Results Fourteen isolated strains were closely related to other reference strains of F genotypes.In SH gene,the homology of nucleotide and amino acid among the fourteen isolated strains were 98.3%-100.0%and 96.5%-100.0%,respectively,and 92.6%%-99.4%and 87.7%-100.0% of homology when compared with that of strains isolated from other provinces in China,respectively.Wsh1 and Wsh2 strains had less homology when compared to other strains of F genotypes.The fourteen strains had homology of 84.5%-85.1%and 77.2%compared to vaccine strains on nucleotide and amino acid,respectively,and had homology of 83.4%-90.9% and 70.1%-86.0% compared to that of other genotypes.In HN gene,the homology of nucleotide and amino acid among the six isolated strains were 99.3%-99.5% and 99.1%-99.7%,respectively,and also 99.8% and 99.8% of homology respectively when compared to the SP strain in China.All the six strains had homology of 92.4%-93.2% and 95.5%-96.4% when compared to the vaecine strains on nucleotide and amino acid,respectively,and had homology of 94.7%-96.8% and 95.5%-99.1%compared to other genotypes.Conclusion Fourteen strains isolated in Yunnan from 2007 to 2009belonged to F genotype of MuV while the HN gene seemed more conservative than SH gene.     

广东省2008－2009 年沙门菌监测

目的 了解广东省腹泻患者中沙门菌的感染及沙门菌暴发的情况以及沙门菌株的血清型别、耐药性和分子特征.方法 对纳入研究的腹泻病患者进行沙门菌的检测,对日常监测中分离到的菌株和暴发监测收集到的菌株进行血清分型、药物敏感试验和脉冲场凝胶电泳(PFGE)分型.结果 2008年共检测1922份粪便标本,分离到7l株沙门菌,阳性率为3.7%;2009年检测2110份粪便标本,分离到85株沙门菌,阳性检出率为4.0%;156株菌共分37种血清型,鼠伤寒和肠炎沙门菌居多;监测到10起由沙门菌污染引起的食物中毒事件,其中有4起由肠炎沙门菌引起,有3起由鼠伤寒沙门菌引起;发现1起疑似肠炎沙门菌暴发,并开展流行病学调查,结果提示4名病例中有2名病例是感染同一来源的肠炎沙门菌;229株沙门菌对头孢类和喹诺酮类抗菌药物敏感率达80%以上,59.3%是多重耐药沙门菌.结论 在广东省引起感染性腹泻和食物中毒的沙门菌主要为肠炎沙门菌和鼠伤寒沙门菌.

Abstract：

Objective To understand the infection of Salmonella (S.) in patients with diarrhea and outbreaks caused by Salmonella to identify the serotypes, resistance to antibiotics and PFGE types of the strains from the surveillance program in Guangdong province. Methods S. strains from patients with diarrhea were detected, and all the positive strains collected in routine and outbreak surveillance programs, were tested by serum agglutination, antibiotic susceptibility and PFGE.Results 71 S. strains were isolated from 1922 stool samples in 2008, with positive rate as 3.7%.85 S. strains were isolated from 2110 stool samples in 2009, with positive rate as 4.0%. All the 156 strains were divided into 37 serotypes, with S. serotype typhimurium and enteritidis as the most common serotypes. 10 incidents of food poisoning were detected, of which 4 were caused by enteritidis and 3 by typhimurium. A suspected outbreak by enteritidis was discovered and under epidemiological investigation. The findings indicated that 2 of the 4 patients from this outbreak were infected with identical enteritidis isolates. 80% of the 229 isolates were found susceptible to cephalosporins and quinoione and 59.3% of them were muitiresistant to the antibiotics. Conclusion S. enteritidis and S. typhimurium were the most common serotypes that caused infectious diarrhoea and food poisoning in Guangdong province.     

新生儿肺炎克雷伯菌脓毒血症细菌的耐药性分析

Objective To study the drug resistance of neonatal sepsis caused by Klebsiella pneumoniae and provide evidence for drug treatment. Method Retrospectively analysis was conducted on the clinical data and antibiotic resistance of Klebsiella pneumoniae in 50 neonates with sepsis. Results The majority of the 50 cases were infected in hospital. There were 13 ESBLs strains in 50 Klebsiella pneumoniae strains (26%), and the others were negative ESBLs starins (74%). All the strains were multidrug-resistance to the β-lactam antibiotics and only sensitive to few antibiotics such as Imipenem and Amikacin. The sensitive rate was 100%. Conclusions The first selected antibiotic for the treatment of neonatal sepsis caused by Klebsiella pnemoniae was Imipenem or Amikacin.     

嗜水气单胞菌TaqMan实时PCR检测方法的建立

Objective To develop a TaqMan real-time PCR for the detection of aeromonas hydrophila. Methods The conserved region of major adhesion gene of aeromonas hydrophila (aha) was used to design primers and TaqMan probe. A total of six concentration gradients for forward and reverse primers ranging from 200 -700 nmol/L were chosen, and four concentration gradients for probe ranging from I00 -400 nmol/L were chosen. And then the concentration of primers and probe were optimized by ANOVA of completely randomized design respectively. The specificity of the established method was evaluated by using bacteria as contrast, including 45 strains Vibrio cholerae,20 strains Vibrio parahemolyticus, 10 strains Vibrio fluvialis,4 strains Vibrio mimicus,5 strains Vibrio vulnificus, 1 strain Vibrio aiginoayticns, 1 strain Vibrio furnissii, 5 strains Salmonella, 10 strains Shigella and 2 strains Piesiomonas shigelloides. The sensitivity, bacterial sensitivity and DNA sensitivity included,were evaluated. The stool of healthy people was contaminated by aeromonas hydrephila artificially, and the ability of the established TaqMan real-time PCR system for detection of aeromonas hydrophila was also evaluated. Results The cycle threshold (Ct) value deserved from 6 groups of primers concentration gradient was (x±s) :20.69±0.33,20.72±0.21,20.81±0. 12,20.74±0.12,20.51±0. 16 and 20.69±0. 11, respectively, and the concentration of forward primer and reverse primer was determined to be 200 nmol/L (F=1.33, P=0. 28). The Ct value deserved from 4 groups of probe concentration gradient was (x±s) : 20.56±0. 08,20.82±0.05,20. 82±0. 11 and 20.93±0.09,respectively,and the concentration of probe was determined to be 100 nmol/L(F =5.26,P =O. 01 ). The bacterial sensitivity and DNA sensitivity were 80 CFU/ml and 100 fg/μl respectively,and the sensitivity to detect aeromonas hydrophila from stool was 8 × 103 CFU/ml, which might be 8 CFU/ml after 8 hours' enrichment. No amplification was observed in the templates of other bacterial. Conclusion The TaqMan real-time PCR method targeting the aha gene of aeromonas hydrophila had a high sensitivity and specificity and might be used to detect aeromonas hydrophila from pure bacterial and stool rapidly.     

副溶血性弧菌引起食物中毒的同源性研究

目的:探讨深圳市龙岗区由副溶血性弧菌O3:K6型引起食物中毒的分子流行病学研究和同源性分析.方法:收集不同地区、不同时期食物中毒事件的副溶血性弧菌菌株,并从7宗相同血清型O3:K6的溶血性弧菌菌株中,每宗取1株副溶血性弧菌进行生化鉴定、血清学分型、脉冲场凝胶电泳(PFGE)分析.结果:7株副溶血性弧菌,它们的血清型均为O3:K6,脉冲场凝胶电泳(PFGE)分析结果显示,有2株副溶血性弧菌图谱一致,具有高度的同源性;5株副溶血性弧菌为紧密相关.结论:通过PFGE分子分型的方法了解到该血清型O3:K6的副溶血性弧菌菌株之间具有紧密相关和高度的同源性,表明副溶血性弧菌血清型O3:K6是该地区引起腹泻的主要菌型.     

脉冲场凝胶电泳对肠球菌的分子检测与同源性分析

目的对40株肠球菌进行分子同源性检测分析,探讨脉冲场凝胶电泳(pulsed field gel electrothoresis, PFGE)在分子流行病学方面的价值. 方法应用PFGE对40株分离自住院患者的肠球菌进行同源性分析. 结果 40株肠球菌经脉冲场凝胶电泳在30～500 kb之间显示12～18条大小不同的DNA片段;40株肠球菌表现出大小不一的同源性:3对肠球菌100%同源,来自同一病房的4对肠球菌分别为78.27%、72.73%、72.73%、80.01%同源;来自不同病房两对肠球菌分别为80.01%、77.78%同源,其余菌株则显示了较低的同源性或者无同源性. 结论 40株肠球菌未见同一克隆的暴发流行;PFGE是细菌分子流行病学分析的理想方法.     

烧伤病房铜绿假单胞菌的耐药检测及脉冲场凝胶电泳分析

目的了解烧伤病房铜绿假单胞菌的耐药性,用脉冲场凝胶电泳对铜绿假单胞菌进行分子流行病学的调查。方法采用琼脂纸片扩散法对9种抗菌药物作敏感试验,其中20株进行脉冲场凝胶分析。结果20株PAE对9种抗菌药物显示很高的耐药率,多重耐药率为30%;20株菌经脉冲场凝胶分析分别有3组菌株具有同源性。结论铜绿假单胞菌对常用抗菌药物耐药率高,多重耐药情况严重,脉冲场凝胶电泳是研究铜绿假单胞菌分子流行病学较好的基因分型方法。     

荧光定量PCR和DNA分子分型在菌痢暴发中的应用

[目的]探讨实时荧光PCR快速检测和脉冲肠凝胶电泳（PFGE）分型方法在菌痢暴发流行病学研究中的应用。[方法]采用实时荧光PCR检测技术对一起菌痢患者的24份肛拭增菌液进行快速检测，同时从患者肛拭中分离的5株福氏4型志贺氏菌采用脉冲场凝脉电泳的方法进行了分子分型。[结果]在这一起菌痢疫情中，实时荧光PCR快速检测24份肛拭增菌液．5份阳性，并从PCR阳性的增菌液中分离到5株福氏4型志贺氏菌，而且5株志贺氏菌的脉冲场凝胶（PFGE）图谱显示DNA条带完全一致，具有高度的同源性。[结论]实时荧光定量PCR技术特异性强，灵敏度高，能在采样后数小时内检测到病原菌的DNA，达到快速诊断的目的。PFGE具有分型能力强，重复性好等特点，能直观地判断致病菌的亲缘关系，及时查明暴发流行的传染源从而有效控制疫情的蔓延，在志贺氏菌的分子流行病学研究中具有重要作用。     

副溶血性弧菌食物中毒的分子分型及耐药性分析

目的对1起副溶血性弧菌引起的食物中毒病原菌进行分子分型及耐药性分析。方法采用脉冲场凝胶电泳进行分子分型,利用药敏卡通过仪器对分离菌株进行药敏检测。结果从患者肛拭分离的9株副溶血性弧菌与可疑剩余食物中的菌株PFGE图谱完全一致,相似度为100％。分离的副溶血性弧菌菌株的耐药结果基本一致：均对氨苄西林耐药,对阿米卡星、庆大霉素、妥布霉素、环丙沙星、左旋氧氟沙星、复方新诺明等敏感,对头孢一代、头孢二代中度敏感,部分头孢三代中度敏感。结论利用脉冲场凝胶电泳对本起副溶血性弧菌引起的食物中毒病原菌进行分子分型,为食源性疾病溯源及分子流行病学研究提供科学依据。     

PFGE在识别和追踪医院感染暴发及流行中的应用

医院感染是危害医疗安全最重要的原因之一，据美国疾病预防控制中心统计每年约有200万住院病人发生医院感染，占住院总数的5％～10％，同时会导致每年约88000人死亡以及带来45亿美元的经济损失，而近年来随着广谱抗生素、肾上腺皮质激素、免疫抑制剂等药物的广泛使用，各种侵入性诊疗措施的不断增多．由多重耐药菌株引起的医院感染暴发流行时有发生，有学者估计可能为5％。     

上海市16个冷却塔水中军团菌脉冲场凝胶电泳分型及基因型监测

目的 研究上海市公共场所16个空调冷却塔水中军团菌的脉冲场凝胶电泳(PFGE)分型,并连续监测该菌基因型变化.方法 2007年5-10月连续6个月以每月1次的频率采样,从16个公共场所空调冷却塔水中分离军团菌,经血清学凝集试验、胶乳凝集试验分型后,使用PFGE技术对酶切后的军团菌全染色体DNA进行电泳获得指纹图谱,利用BioNumerics软件进行聚类分析.结果 16个冷却塔水中共分离出131株军团菌,包括嗜肺军团菌、博杰曼军团菌、米克戴德军团菌和茴香军团菌,分为52个PFGE型别,其中37个PFGE型别(71.15%)仅分布于1个冷却塔中,即为该冷却塔所特有;15个PFGE型别(28.85%)分布于2个或以上冷却塔中.16个冷却塔具有2个或以上的PFGE型,13个冷却塔(81.25%)中多次出现相同的PFGE型别.2007年6-10月连续5个月从6个冷却塔中分离出18株PFGE型为LPAs.SH0078型的军团菌.结论 冷却塔水中的军团菌基因型具有多样性和复杂性,81.25%的冷却塔水中PFGE型具有持续性,且LPAs.SH0078型广泛分布,可能为优势PFGE型.     

北京市2010年细菌性痢疾病原学分析

目的掌握北京市2010年细菌性痢疾的血清学分布以及脉冲场凝胶电泳技术(PFGE)分子分型特征,为流行病学研究提供合理依据。方法从形态特征、生化反应、血清分型、PFGE分子分型方面对北京市6个区的肠道多病原监测点分离到的195株志贺菌进行了系统鉴定和病原学分析。结果 195株志贺菌包括福氏志贺菌33株(16.92%)、宋内志贺菌162株(83.08%);福氏志贺菌血清型以F2a为主。7、8、9三个月志贺菌的发病率最高。选择其中55株宋内志贺菌进行脉冲场凝胶电泳分析,结果显示55株菌可以分为27个带型,其中以J16X01.BJ0016带型(11株)和J16X01.BJ0011(7株)为主。结论北京市2010年6个监测区县分离到的志贺菌包括福氏和宋内2种血清群,以宋内志贺菌为优势血清群,福氏志贺菌以F2a血清型为主。8月份为志贺菌高发季节。J16X01.BJ0016为宋内志贺菌PFGE优势型别。     

Novel ctxB variants of Vibrio cholerae O1 isolates,China

We screened 650 isolates from historical collection of Vibrio cholerae O1 during the 7th cholera pandemic in China, by amplifying and sequencing the cholera toxin subunit gene ctxB. Ten isolates were identified as harboring three novel ctxB genotypes based on amino acid residue substitutions. Within them one isolate from a patient in 1964 was similar to the El Tor genotype, except for an 11 amino acid repeat sequence (LAGKREMAIIT) that was inserted after position 62. Six environmental isolates from different regions and years were identified as the Australia El Tor genotype, except at positions 36(T → A), 39(H → Y), and 55(K → N), while three environmental isolates were similar to genotype 5, except at position 24(Q → H). Sequencing of rstR, the marker gene for the CTXΦ allele typing, revealed that two isolates carried the rstR gene of the El Tor type, five carried the classical type rstR, while other isolates carried the rstR232 type. All 10 isolates contained the repeat in the toxin gene rtxC, an El Tor biotype-specific marker, and the El Tor toxin-coregulated pili subunit A gene tcpA, showing the El Tor traits of these isolates. Additionally, by phenotypic biotyping (susceptibility to polymyxin B, positive for chicken erythrocyte agglutination, and Voges–Proskauer test), all isolates except two were typical of the prototype El Tor isolate, while these two isolates had mixed classical phenotypes (hybrid biotype). Furthermore, pulsed-field gel electrophoresis analysis suggested that the new ctxB altered isolates possessed potential transmissibility and thatthey propagated in the local region(s). Taken together, these novel ctxB variants of V. cholerae O1 experienced complex hybrid and genetic exchange but belong to the El Tor lineage, and the pathogenic and epidemic potential of these lineages should be monitored.