Prevalence and Study of the Clonality of Extended-Spectrum Beta-Lactamase-Producing Klebsiella pneumoniae Strains in Neonatology at the University Hospitals of Abidjan by the Pulsed Field Gel Electrophoresis and the Quantitative Antibiogram

Background: ESBL-producing strains of Klebsiella pneumoniae, one of the main causes of nosocomial and hospital-acquired infections, are commonly associated with therapeutic impasses. Surveillance of these multidrug-resistant pathogens is a crucial tool for controlling and preventing infections. This surveillance involves the use of appropriate molecular and phenotypic typing techniques. The choice of techniques is based on criteria such as discriminatory power, intra- and inter-laboratory reproducibility, epidemiological concordance, ease of use and cost. The aim of our study was to identify clusters of Extended-Spectrum Beta-Lactamase-producing Klebsiella pneumoniae (ESBL-K. pneumoniae) strains circulating in neonatology using quantitative antibiogram (QA) and Pulsed Field Gel Electrophoresis (PFGE). Materials and Methods: This cross-sectional study included 55 K. pneumoniae strains isolated from a total of 513 samples. These various samples are taken from newborns, healthcare personnel, and the environment. K. pneumoniae identification followed standard bacteriological procedures and was confirmed using the Vitek® 2 (bioMérieux). The detection of the ESBL phenotype was performed using the synergy test. QA and PFGE were used to identify clonal relationships between the various strains isolated. Concordance between these two methods was assessed by calculating Cohen’s KAPPA coefficient and Simpson’s diversity index. Results: Among the 55 K. pneumoniae strains included in this study, 58.2% (32/55) were found to be Extended-Spectrum Beta-Lactamase (ESBL) producers. Most of these strains were isolated from neonatal samples (blood samples and rectal swabs). The quantitative antibiogram method applied to 28 out of the 32 ESBL-producing strains revealed that the isolates were grouped into 5 clusters. Pulsed Field Gel Electrophoresis performed on a total of 16 ESBL-producing strains showed the existence of four profiles. A perfect concordance was observed between the two methods. Conclusion: The results of this study highlighted the existence of clonal strains of various origins within neonatology units.

Establishment and Comparison of Pulsed-field Gel Electrophoresis,Multiple-locus Variable Number Tandem Repeat Analysis and Automated Ribotyping Methods for Subtyping of Citrobacter Strains

Objective To establish and compare the pulsed-field gel electrophoresis （PFGE）, multiple-locus variable number tandem repeat analysis （MLVA） and automated ribotyping for subtyping of Citrobacter strains. Methods PFGE protocol was optimized in terms of plug preparation procedure, restriction enzymes and configuration of electrophoretic parameters. MLVA method was evaluated by finding variable number tandem repeats in two genomes of Citrobacter strains. The ribotyping was performed by using the automated RiboPrinter system. Results We optimized the plug preparation procedure, focused on the cell suspension concentration （turbidity of 2.5 to 3.5）, SDS addition （no SDS needed） and lysis time （1 h）, and selected the appropriate restriction enzyme （Xbal） and the electrophoretic parameters （1.0 s-20.0 s for 19 h） of PFGE. There was nearly no discriminatory power of MLVA between Citrobacter strains. For 51 Citrobacter strains, automated ribotyping gave a D-value of 0.9945, while PFGE gave a D-value of 0.9969. Both PFGE and automated ribotyping clustered strains from the same sources （with the same species from the same place at the same time identified as the same source） and divided strains from different sources （from different years, places and hosts） into different subtypes. Conclusion PFGE protocol established in this paper and automated ribotyping are suitable for application in Citrobacter subtyping.

Optimization of Pulse-Field Gel Electrophoresis for Borrelia burgdorferi Subtyping

Objective To optimize the performance of Pulsed-Field Gel Electrophoresis （PFGE） for the comparison of inter-laboratory results and information exchange of Borrelia burgdorferi subtypingo Methods A panel of 34 strains of B. burgdorferi were used to optimize PFGE for subtyping. In order to optimize the electrophoretic parameters （EPs）, all 34 strains of B. burgdorferi were analyzed using four EPs, yielding different Simpson diversity index （D） values and the epidemiological concordance was also evaluated. Results The EP of a switch time of l s to 25 s for13 h and l s to10 s for 6 h produced the highest D value and was declared to be optimal for Mlul and 5mal PFGE of B. burgdorferi. Mlul and Smal were selected as the first and second restriction enzymes for PFGE subtyping of B. burgdorferi according to discrimination and consistency with epidemiological data. Conclusion PFGE can be used as a valuable test for routine genospecies identification of B burgdorferi.

CHARACTERIZATION OF PATHOGENIC FUNGI GENOMES USING PULSED FIELD GEL ELECTROPHORESIS

Pulsed field gel electrophoresis(PFGE) has been firstly introduced in characterization of the pathogenic fungi Penicillium marne f fei and Exophiala dermatitidis genomes.The numbers and sizes of their chromosomes have been detected.Polymorphism was identified on the smallest chromosome of E.dermatitidis.The result shows that PFGE for characterization of large molecular DNA pathogenic fungi is very suitable,it is more simple and more efficacy.The result also shows the diversity of pathogenic fungi is relative common even in rare occurred pathogenic fungi such as E.dermatitidis.

Antimicrobial resistance, genotypic characterization and pulsed-field gel electrophoresis typing of extended spectrum β-lactamases-producing clinical Escherichia coli strains in Macao, China

Background The rise of the production of CTX-M class extended spectrum β-lactamases （ESBLs） has been well documented in traveling countries but no data are found for Macao, an international travel city. The objectives of this study were to identify the antimicrobial resistance pattern, and determine the prevalence, genotype and clonal relationship of ESBLs in 209 clinical Escherichia coli strains from Macao, China. Methods Antimicrobial susceptibility test was performed to determine the resistance patterns of the isolates using the disk diffusion method with 17 antimicrobial agents. Phenotypic detection was screened and confirmed according to the Clinical and Laboratory Standards Institute. Genotypic characterization was detected by isoelectric focusing analysis, polymerase chain reaction and sequencing. The clonal relationship between the different ESBL isolates was studied by pulsed-field gel electrophoresis （PFGE）. Results Imipenem and meropenem exhibited 100% susceptible among 209 strains. Overall, 82.3%, 67.3%, 52.9%, 51.2% and 51.0% of the isolates displayed resistance to ampicillin, tetracylcline, ciprofloxacin, sulfamethoxazole trimethoprin and gentamycin. The prevalence rate of ESBLs was 30.1%. Antibiotic resistances were found to be significantly higher among the ESBL producing group compared to non-ESBL producing group. We detected CTX-M-14 to be the major genotypic characterization of ESBLs （76.2%）. Two strains showed indistinguishable patterns by PFGE. Conclusions The prevalence of antimicrobial resistance is alarming high in Macao. Antimicrobial resistance is significantly higher among the ESBL producing group. This study documented CTX-M-14 as the predominant ESBL type. Although indistinguishable pattern was found between two strains, it was too small to decide whether any of the investigated strains was epidemic. Our findings may be also pertinent for other geographic areas undergoing similar travel characteristics to understand the corresponding effects on bacterial populations.

Sorting Semiconducting Single-Walled Carbon Nanotubes by Water-Soluble Polyfluorene Assisted Electrophoresis and Its Application in Field-effect Transistors

We report a considerably promising method based on agarose gel electrophoresis （AGE） to separate single-walled carbon nanotubes by adding a water-soluble polyfluorene （w-PFO） as surfactant into the agarose gel. In this effective method, the AGE/w-PFO gel network will trap more semiconducting single-walled carbon nanotubes （SWNTs） with the assistance ofw-PFO, for the strong interaction between w-PFO and semiconducting species. The optical absorbance, photoluminescence emission and resonant Raman scattering characterization were used to ver- ify the separation effect. The purity of separated semiconducting species is as high as （98±1）%. The demonstrated field effect transistors give the on/off ratio and mobility about 27000 and 10.2 cm^2·V^-1·s^-1, respectively.

副溶血性弧菌引起食源性疾病暴发事件调查与病原特征分析

目的调查和分析山西省阳泉市一起食源性疾病暴发事件中副溶血性弧菌的病原特征,提高对食物中毒应急事件的处理能力。方法使用脉冲场凝胶电泳(PFGE)、血清学分型、毒力基因检测、药物敏感实验和全基因组测序的方法分析25例有腹泻、腹痛、恶心、呕吐等消化道症状的患者分离出的11株分离菌株。结果11株分离菌株均为副溶血性弧菌,其中8株副溶血性弧菌分离株携带毒力基因tdh,1株同时携带毒力基因trh和tdh,1株只携带毒力基因trh,1株只有毒力基因tlh。血清型分为3种型别,分别是O10:K4、O4:K63以及O5:unknown。根据11株副溶血性弧菌的PFGE图谱将菌株分为5种不同的群,基于全基因组序列的分析显示8株来自患者的副溶血性弧菌具有相同的ST型,属于同一克隆群。副溶血性弧菌病原体毒力、耐药基因和药敏表型相同,符合暴发流行病学特征,判断其为该起食物中毒事件的病原体。11株菌均只含有blaCARB耐药基因,且未检测到耐药质粒,对氯霉素、萘啶酸、四环素、美罗培南、阿米卡星、氨苄西林、厄他培南、替加环素、头孢噻肟、头孢他啶和环丙沙星均敏感,对多黏菌素E中度敏感,均无耐药表型。结论这是一起由多种血清型副溶血性弧菌污染了食品而导致的食源性疾病暴发事件。该食堂储存食物时生熟不分,副溶血性弧菌机会性繁殖在合适的含盐食物中也可以增殖,进而引起该起事件发生。

1起ST19型鼠伤寒沙门氏菌引起的食物中毒调查、溯源分析与探讨

目的分析武汉市某区1起食物中毒事件的致病原因,探讨分离菌株之间的分子流行病学关系,为食源性疾病暴发溯源和临床诊治提供参考依据。方法采集食物中毒相关样本20份,提取样本总DNA进行18种食源性致病菌多重PCR检测,同时按时GB4789.4-2016进行病原菌分离鉴定;应用传统玻片凝集法和微量肉汤稀释法对阳性菌株进行血清型分型和耐药性检测,并提取所有菌株核酸进行全基因组测序组装,利用Abricate和SeqSero在线预测每株菌的血清型和耐药基因,然后与传统方法进行比较分析。对分离的9株沙门氏菌分别采用脉冲场凝胶电泳(PFGE)和全基因组序列方法(WGS)递进分析。结果共检出12株沙门氏菌(菌株编号DXH001~DXH012),其中病例肛拭子样本7份、病例粪便样本2份,工作人员肛拭子样本3份。常规血清型分型均为B群鼠伤寒沙门氏菌,与全基因组测序鉴定分型结果一致。12株菌株耐药谱完全一致,对阿米卡星、氨苄西林、头孢唑啉、庆大霉素、哌拉西林、四环素均耐药。基于全基因组预测的氨基糖苷类、头孢菌素、青霉烷、四环素的耐药性与耐药表型结果完全一致。选取DXH001~DXH009开展PFGE和WGS分析。9株鼠伤寒沙门氏菌获得完全一致的PFGE图谱,全基因组序列大小无明显差异,约为4.9 Mbp,MLST型均为ST19。从SNP的最小生成树来看共存在17个变异位点,各菌株间SNP差异数为1~6。全基因组系统发育进化树分析显示,9株沙门氏菌自成一簇,与数据库其他沙门氏菌相差甚远,属于新的克隆分支。同源性最高的来源于江西的GCF_020221795.1参考样本。结论本次食物中毒事件致病源为鼠伤寒沙门氏菌ST19,为同一暴发来源。9株沙门氏菌遗传距离较近,但与数据库中其他沙门氏菌遗传距离较远,自成一簇属于新的克隆分支。本研究中沙门氏菌具有多重耐药性,需加强对多重耐多药菌株的监控及抗菌药物使用的监管。

云南省2016—2022年志贺氏菌分子分型及耐药性分析

目的对云南省2016—2022年食源性疾病主动监测分离的志贺氏菌进行血清、分子分型和药敏试验等分析,了解云南省志贺氏菌的病原学特性,为志贺氏菌感染的防控和治疗提供数据支持。方法2016年1月至2022年12月从患者粪便中分离志贺氏菌,采用玻片凝集法进行血清学分型,脉冲场凝胶电泳(PFGE)进行分子分型分析,微量肉汤稀释法进行药敏试验。结果共分离志贺氏菌89株,其中福氏志贺氏菌占52.81%,宋内志贺氏菌占47.19%。PFGE分析发现,2种志贺氏菌均分为A和B 2个聚类簇,B簇为优势簇。47株福氏志贺氏菌分为30种PFGE带型,有3组优势带型,42株宋内志贺氏菌分为22种PFGE带型,有4组优势带型,并识别两起疑似暴发事件。志贺氏菌对13种抗生素存在不同程度的耐药,78.65%的菌株为多重耐药菌株。结论云南省志贺氏菌PFGE优势带型明显,部分带型聚集分布。耐药形势严峻,多重耐药现象严重。福氏志贺氏菌和宋内志贺氏菌耐药表型存在差异。

2022—2023年贵州省单核细胞增生李斯特氏菌PFGE分型及耐药性分析

目的了解2022—2023年贵州省单核细胞增生李斯特氏菌血清表型、脉冲场凝胶电泳(pulse-field gel electrophoresis,PFGE)分子分型特征和耐药情况,旨在为贵州省李斯特氏菌病的防控提供实验室数据支持并提高预警监测能力。方法收集2022年1月—2023年12月贵州省致病菌识别网中心实验室监测腹泻疾病相关样本1220份,按照GB 4789.30—2016《食品安全国家标准食品卫生微生物学检验单核细胞增生李斯特氏菌检验》的执行标准分别进行分离培养,按照《国家致病菌识别网实验室监测技术手册(2022试用版)》进行实时荧光聚合酶链反应(polymerase chain reaction,PCR)检测方法鉴定,多重PCR检测血清型分型、PFGE分子分型和药敏试验。结果1220份腹泻疾病相关样本分离出424株菌株,其中单核细胞增生李斯特氏菌11株,阳性率为2.59%(11/424);11株单核细胞增生李斯特氏菌分为6种血清表型,血清型分布为1/2a、1/2b、1/2c、3a、3b和3c型;11株单核细胞增生李斯特氏菌对头孢西丁(cefoxitin,FOX)耐药率高达100%,对氯霉素(chloroamphenicol,CHL)中介率为72.72%,剩余12种药物[红霉素(erythromycin,ERY)、复方新诺明(trime-thoprim/sulfamethoxazole,T/SUL)、庆大霉素(gentamicin,GEN)、亚胺培南(imipenem,IPM)、苯唑西林(benzoxacillin,OXA)、克林霉素(clindamycin,CLI)、环丙沙星(ciprofloxacine,CIP)、达托霉素(datomycin,DAP)、氨苄西林(ampicillin,AMP)、四环素(tetracycline,TET)、万古霉素(vancomycin,VAN)、青霉素(chloramphenical,PEN)]均100%敏感;经AscⅠ酶切后11株单核细胞增生李斯特氏菌分成7种PFGE带型,相似性为40%~100%,其中3株菌相似性高达100%。结论2022—2023年贵州省发生了一起家庭聚集性李斯特氏菌病事件,遵义市肉制品中存在相同的污染来源,且污染源持续存在,贵州省具有多种致病性单核细胞增生李斯特氏菌,但尚未出现严重耐药情况。

一起由副溶血性弧菌引起的食物中毒事件的病原检测及溯源分析

目的:对一起农村自办婚宴发生的食物中毒事件进行病原检测及溯源分析。方法:对采集的粪便、肛拭子、手涂抹样等样本进行病原学检测,对检出的副溶血性弧菌进行血清凝集、3种毒力基因检测、MIC药敏试验和PFGE分型。结果:该起食物中毒事件共涉及10例病例,发病时间较集中,首末病例发病时间间隔4.75 h,患者主要症状为腹痛、腹泻、恶心、呕吐等。采集的样本中共检出5株副溶血性弧菌,分为3种血清型,4种PFGE型,毒力基因均为tlh+tdh+trh-,对头孢唑啉全部耐药。结论:该起农村自办婚宴食物中毒事件由副溶血性弧菌感染引起。

低压静电场处理对鱿鱼保鲜效果的影响

为探究低压静电场(low voltage electrostatic field,LVEF)处理对鱿鱼贮藏品质的影响,采用pH值、蒸煮损失率、挥发性盐基氮(total volatile basicnitrogen,TVB⁃N)和硫代巴比妥酸(thiobarbituric acid,TBA)等评价指标,以无电场处理的样品为对照组,研究比较低压静电场贮藏条件下的鱿鱼品质变化情况。结果表明,低压静电场处理能够改善鱿鱼的贮藏品质。随着贮藏时间的延长,LVEF组的样品pH值增加缓慢;贮藏期间对照组的蒸煮损失率、TVB⁃N值始终低于LVEF组,且当贮藏至15 d时LVEF组的TBA值远低于对照组的1.24 mg/kg;低压静电场对微生物繁殖有明显的抑制作用,贮藏15 d内LVEF组菌落总数均低于6 lg(CFU/g);在硬度、弹性、感官评价和蒸煮损失率上LVEF组均优于对照组。此外,十二烷基硫酸钠⁃聚丙烯酰胺凝胶电泳分析显示LVEF组条带未发生明显变化,故低压静电场处理能更好地保持鱿鱼品质。

遵义市食源性沙门菌分子分型及耐药研究

目的了解遵义市食源性沙门菌分型及耐药特征。方法收集遵义市2020-2022年食源性沙门菌,采用玻片凝集法对沙门菌进行血清分型,利用脉冲场凝胶电泳(PFGE)对沙门菌进行分子分型,采用肉汤稀释法对沙门菌进行耐药监测,应用BioNumerics软件进行数据分析。结果收集的21株沙门菌分为16种血清型,其中肯塔基沙门菌3株、德尔卑沙门菌2株、肠炎沙门菌2株、希林登沙门菌2株,其余均为1株。PFGE结果显示带型呈现多态性,同源性最高为62.96%。药敏试验结果显示食源性沙门菌对氨苄西林耐药率最高,为71.43%,其次对四环素耐药率达61.90%,多重耐药率为76.19%。结论遵义市食源性沙门菌血清型和遗传性多样,对抗菌药物的耐药率高,多重耐药严重。

丰城市食源性沙门氏菌的血清型、耐药性及同源性分析

目的探究丰城市食源性沙门氏菌的血清型分布特征、耐药性分析及脉冲场凝胶电泳(PFGE)分子溯源分析,为食源性疾病的暴发预警提供科学依据。方法对丰城市2015年4月至2022年11月分离来自食品和腹泻患者的沙门氏菌进行血清学分型以及耐药性分析,应用PFGE分析菌株之间的同源关系。结果在756份食品和806份腹泻患者样品中,共检出沙门氏菌49株,其中鼠伤寒沙门氏菌占比率为38.78%,其次肠炎沙门氏菌占比率为32.65%。选取的35株沙门氏菌对氨苄西林耐药率最高,耐药率达到82.86%,其次是对头孢唑啉和萘啶酸耐药率达到48.57%,其中30株具有多重耐药性(30/35,85.71%)。49株沙门氏菌DNA指纹图谱同源性为55.4%~100.0%。结论丰城市从食源性分离到的沙门氏菌株主要以鼠伤寒沙门氏菌和肠炎沙门氏菌为主,耐药和多重耐药存在严重,应加强对抗生素规范使用,DNA指纹图谱显示沙门氏菌较高同源性,需加强PFGE的日常监测为沙门氏菌的食品安全风险提供预警。

院内多重耐药鲍曼不动杆菌分子流行病学和耐药性研究

目的分析院内临床和环境多重耐药鲍曼不动杆菌(MDRAB)的耐药机制和分子流行病学特征,为预防和控制MDRAB的传播提供依据。方法收集2020年5月至2021年4月院内临床及环境分离到的非重复MDRAB菌株34株,其中临床标本25株,环境标本9株。应用PCR和测序方法检测MDRAB的耐药基因。多位点序列分型(MLST)和脉冲场凝胶电泳(PFGE)对MDRAB进行分子分型。结果34株MDRAB阳性基因携带率分别为:blaOXA23、blaOXA-51及blaOXA64gp均为100%,TEM 85.3%(29/34)。25株临床MDRAB监测到7个ST序列类型:分别为ST540(10/25)、ST195(5/25)、ST369(3/25)、ST208(2/25)、ST381(2/25)、ST938(2/25)和ST451(1/25);6个克隆群:分别为A群(9/25)、D群(8/25)、C群(4/25)、F群(2/25)、E群(1/25)、G群(1/25)。9株环境MDRAB监测到2个ST序列类型:ST208(8/9)、ST540(1/9);2个克隆群:B群(8/9)、C群(1/9)。结论院内MDRAB主要来源于重症监护病房,blaOXA-51-Like+blaOXA-23+blaTEM-like是主要碳青霉烯耐药模式。院内临床流行的主要序列类型为ST540和ST195,主要的克隆群为A群、D群。ST540、A克隆群MDRAB贯穿整个研究阶段且在多个重症监护病区播散流行。临床与环境MDRAB主要流行的ST序列型和克隆群存在差异。

潮州市临床沙门氏菌的耐药性和分子分型

为了研究引起潮州市临床患者腹泻沙门氏菌的血清型分布、耐药谱和分子分型特征,对2021年分离自广东省潮州市的定点监测医院腹泻患者的55株沙门氏菌,采用血清凝集法鉴定血清型、微量肉汤稀释法检测对17种抗生素的敏感性,脉冲场凝胶电泳对菌株进行分子分型.结果显示,在55株沙门氏菌中,主要的血清型为鼠伤寒沙门氏菌,占41.82%;其次是胥莱士亥姆沙门氏菌和瓦根尼亚沙门氏菌,均占10.91%.药物敏感性试验表明,菌株对氨苄西林/舒巴坦的耐药率最高,达80.00%;其次是四环素、氯霉素和复方新诺明,分别为76.36%、50.91%和49.09%.在55株沙门氏菌中,48株沙门氏菌经XbaⅠ内切酶处理后获得分子分型结果.它们共产生47个PFGE带型,呈现高度多态性,没有明显的优势PFGE带型.该研究结果提示引起腹泻的沙门氏菌血清型以鼠伤寒沙门氏菌为主.PAGE分子分型散在分布,表明潮州市沙门氏菌总体呈散发多态性,没有形成大规模的流行.值得关注的是,对抗生素耐药性及多重耐药性严重,应当引起重视并持续开展耐药及病原学监测.

基于磁流变胶泥磁电阻效应的转速检测实验研究

转速是评估旋转机械运行状态的一个重要参数,针对转速检测,本文提出一种基于磁流变胶泥磁电阻效应的转速传感器。由旋转磁场单元与敏感单元组成转速传感器的主体结构,利用静态及动态磁电阻实验研究敏感单元的磁电阻特性,从微观结构层面分析了磁电阻效应机理,推出了敏感单元电阻与激励磁场之间的关系;针对传感器的结构特点建立转速实验测试系统,通过直流电桥的输出电压信号表征被测转速;研究表明:软磁颗粒含量及激励磁场的强度都对敏感单元磁电阻效应有显著影响,随着被测转速的增大,传感器输出电压信号峰峰值具有较好的线性衰减特性,以磁流变胶泥为核心敏感材料的转速传感器可实现对中低转速的有效检测。

移动性多黏菌素耐药基因介导的大肠埃希菌药敏特点与同源性分析

目的分析多黏菌素耐药大肠埃希菌的耐药机制、药敏特点及其同源性,为有效预防和控制其暴发及流行提供分子流行病学依据。方法收集2016年5月至2022年6月分离自临床的多黏菌素耐药大肠埃希菌,应用PCR技术筛选移动性多黏菌素耐药基因(mobile colistin resistance,MCR),采用微量肉汤稀释法测定最小抑菌浓度。收集患者的临床资料,利用脉冲场电泳技术(PFGE)对收集到的菌株进行同源性分析并对其中1株进行全基因组测序分析。结果分离并鉴定出4株携带有MCR-1基因的多黏菌素耐药大肠埃希菌,4株菌株除了对替加环素均敏感外,对于临床常见的绝大多数抗生素均表现出不同程度的耐药。临床资料分析均未发现患者有多黏菌素使用史。该4株菌可分为2种类型,其中A型3株,B型1株。对其中1株菌进行全基因组测序分析发现MCR-1基因位于约70 kb的质粒上。结论携带MCR-1基因的多黏菌素耐药大肠埃希菌具有克隆传播的潜在威胁,对临床常见抗生素均表现出较高的耐药性,为临床治疗带来极为严重的挑战,需要加强防护措施,防止其暴发流行。

Phylogenetically clustering of rhizobia by genome structure:application to unclassified Rhizobium

Previous research reveals that the genome structures of rhizobial type strains and reference strains can reflect their phylogenetic relationships. In order to further explore the potential application of genome structure as a phylogenetic marker in rhizobial natural taxonomy, this study analyzed the genome structures of 29 unclassified nodule bacteria isolated from the root nodules of leguminous trees, Robinia sp., Dalbergia spp., and A lbizia spp. and 7 rhizobial reference strains by I-CeuI cleavage, then clustered these bacteria phylogenetically based on their genome structures and compared these clusters with those based on numerical taxonomy and 16S rDNA PCR-RFLP. Eleven phylogenetic clusters were obtained, The clusters were in large part consistent with those based on numerical taxonomy and 16S rDNA PCR-RFLP. Also there are inconsistent clusters based on the above three methods. But results are completely consistent with 16S rRNA clusters. This suggested that the genome structure clustering method can be used to lastly identify root nodule isolates and detect their phylogenetic relationships. The credibility and repeatability of the results, together with the simplicity and possibility to analyze a large number of strains in a short time of the method, indicates the broad potential application of genome structure as phylogenetic marker to categorize rhizobial isolates and should in the future facilitate biodiversity studies.

一起肠炎沙门氏菌感染的食源性疾病暴发事件的溯源分析及药敏检测

目的对一起因食用肠炎沙门氏菌污染的熏肉大饼引起的食源性疾病暴发事件进行溯源分析。方法对8例患者进行流行病学调查,采集相关环境、食品及粪便等样本,根据国家标准进行实验室检测,经增菌后挑取可疑菌落进行生化鉴定,对检出的6株沙门氏菌株采用标准诊断血清进行血清凝集试验,药敏试验及脉冲场凝胶电泳。结果该起事件发病8例,6份样本中,分离出肠炎沙门氏菌,沙门氏菌检出率食品、环境和病人粪便样本均为100%,药敏试验结果显示,耐药谱为多粘菌素E(Colistin,CT)―头孢噻肟(Cefotaxime,CTX)―四环素(Tetracycline,TET)―环丙沙星(Ciprofloxacin,CIP)―氨苄西林(Ampicillin,AMP)―氨苄西林/舒巴坦(Ampicillin/Sulbactam,AMS),均呈现6重耐药现象,对氯霉素(Chloramphenicol,CHL)、复方新诺明(Sulfamethoxazole,SXT)、厄他培南(Ertapenem,ETP)、美罗培南(Meropenem,MEM)、头孢他啶(Ceftazidime,CAZ)、头孢他啶/阿维巴坦(Ceftazidime/avibactam,CZA)、替加环素(Tigecycline,TIG)、阿奇霉素(Azithromycin,AZM)、阿米卡星(Amikacin,AMI)敏感,6株菌的脉冲场凝胶电泳(Pulse Field Gel Electrophoresis,PFGE)条带一致,同源性100%,显示为同一克隆。结论该起事件为市民食用被肠炎沙门氏菌污染的熏肉大饼引起的食源性疾病暴发事件。