Fimbriation and curliation in Escherichia coli O157:H7: a paradigm of intestinal and environmental colonization

Shiga toxin-producing Escherichia coli (STEC) serotypes, particularly E. coli O157:H7, possess a variety of fimbrial and afimbrial adhesins which have emerged as important contributors to intestinal colonization. E. coli O157:H7 possesses two chromosomal operons encoding long polar fimbriae (Lpf), which have been found to influence adherence in vitro and colonization in vivo. In a recent Infection and Immunity paper, we further explored the role of Lpf in E. coli O157:H7 intestinal colonization by using the infant rabbit model of STEC infection. We found that an E. coli O157:H7 Lpf-deficient mutant was outcompeted in the rabbit intestine by its parental strain, which may suggest that Lpf contributes to colonization. In contrast, the Lpf-deficient mutant showed an increased adherence to cultured intestinal epithelial cells, and we discovered that this strain overexpressed curli fibers. In this addendum article, we provide a continued perspective on the predicted roles of Lpf and curli, both in vivo and in vitro.     

出血性大肠杆菌O157菌壳的制备研究

目的利用温度控制噬菌体PhiX174裂解基因E的表达,制备出血性大肠杆菌O157∶H7菌壳,鉴定其裂解效率并观察其形态。方法利用PCR技术扩增得到噬菌体PhiX174裂解基因E并克隆到质粒pBV220中,将重组质粒导入出血性大肠杆菌O157∶H7。重组菌株O157∶H7(pBV220::E)培养温度从28℃突升至42℃,每20min检测菌液OD600值,绘制重组菌株生长曲线。体外菌落计数计算裂解效率,并通过电镜观察菌壳结构。结果获得了PhiX174裂解基因E全长基因及重组质粒,构建了大肠杆菌的重组菌株。重组菌菌液OD600值在温度突升至42℃后40min后开始显著下降,80min后OD600值趋于平稳。细菌的裂解效率为98.4%。电子显微镜观察显示,经诱导后,O157∶H7细菌内容物可以通过细菌表面的孔道流出,从而形成菌壳。结论本研究成功制备了大肠杆菌O157∶H7菌壳,为将来进一步研究O157菌壳的特性奠定了基础。     

大肠杆菌O157∶H7 CVa9株O抗原变异的研究

目的　研究本实验室保藏的大肠杆菌O15 7:H7(E coliO15 7:H7)日本分离株CVa9O抗原的变异。方法　血清凝集试验检测CVa9菌株O和H抗原 ,区分O抗原变异株与非变异株。聚合酶链反应 (PCR)法分别检测O15 7和H7特异性基因。生化试验检测生化特性。观察菌株在麦康凯、山梨醇麦康凯、棉子糖麦康凯及ChromagarO15 7显色培养基上菌落形态 ,菌落计数法计算变异率。结果　抗 -O15 7抗血清与CVa9菌株进行玻片凝集试验出现强凝集 (CVa9- 8)和不凝集 (CVa9- 1、CVa9- 15 )两种菌落 ,试管凝集试验结果相同 ,证实不凝集菌落O抗原发生变异。抗 -HT 抗血清分别与变异株和非变异株H抗原进行试管凝集试验 ,均为强凝集。两种菌株O15 7和H7特异性基因均为阳性。变异株与非变异株生化特性基本相同 ,但变异株不发酵棉子糖。两种菌株在麦康凯及山梨醇麦康凯培养基上菌落形态特征没有区别。在ChromagarO15 7显色培养基上培养 4 8h ,变异株为浅紫红色 ,菌落周边呈毛边状 ,非变异株为紫红色 ,菌落边缘整齐。变异株在用棉子糖代替乳糖制备的棉子糖麦康凯培养基上菌落呈粉红色 ,非变异株呈红色。菌落计数显示变异率为 99 80 %。结论　CVa9菌株在保存过程中O抗原发生变异 ,菌落形态及部分生化特征亦有所改变。变异株和非变异株均携带O15     

O157大肠埃希菌食品分离株的特征研究

目的掌握福建省E.coliO157∶H7和O157∶H?食品分离株的毒力基因携带状况、PFGE分型特征、抗生素的药敏谱以及产志贺毒素的E.coliO157∶H7菌株的细胞毒性状况。方法分离菌株经VITEK全自动生化系统鉴定;O157和H7单克隆诊断血清凝集;PCR法检测O157、H7抗原基因及毒力因子基因;菌株的分型用PFGE方法进行;采用CLSI推荐的K-B法对菌株进行15种抗生素的药敏试验;对产志贺毒素的分离株用Vero细胞和Cyto Tox 96R○试剂盒进行细胞毒性检测。结果2株E.coliO157∶H7,其O157、H7及Stx2、Hly、eaeA毒力基因均阳性,Stx1基因均阴性;另3株E.coliO157∶H?,其O157基因阳性,H7和Stx1、Stx2、Hly、eaeA毒力基因均阴性;5株菌的PFGE带型各不相同,2株E.coliO157∶H7的同源性较高,达81%;菌株对15种常用抗生素较为敏感,链霉素、甲氧苄啶敏感率稍低为40%,其余敏感率达60%～100%。2株产志贺毒素的菌株对Vero细胞有毒性作用,细菌细胞比位50:1时细胞毒性百分比分别为61.25%和67.80%。结论本省在外环境动物性食品中存在产志贺毒素的E.coliO157∶H7菌株,提示应加强E.coliO157∶H7的监测,预防该菌在本省人间的感染和流行。     

从熊猴肺脏中检出大肠埃希氏菌O157：H7

西安市动物园于１９９８年７月５日死亡熊猴１只,从送检标本熊猴肺脏中分离的菌株经生物学及血清不窒面鉴定,证实为大肠埃危机 氏菌Ｏ１５７：Ｈ７。该菌是引起熊猴死亡的病原菌。     

Characterization and Food Application of the Novel Lytic Phage BECP10: Specifically Recognizes the O-polysaccharide of Escherichia coli O157:H7

Escherichia coli O157:H7 is a global concern that causes serious diseases, such as hemolytic uremic syndrome and bloody diarrhea. To control E. coli O157:H7 in food, a novel siphophage, BECP10, that targets the O157 serotype was isolated and characterized. Unlike other E. coli phages, BECP10 can only infect E. coli O157 strains, and thus, did not infect other strains. The 48 kbp genome of BECP10 contained 76 open reading frames (ORFs), including 33 putative functional ORFs. The phage did not contain lysogeny-related modules or toxin-associated genes, suggesting that the phage might be strictly lytic. The tail spike protein (TSP) sequence had very low homology with the reported T1-like phages, indicating that TSP might be related to this unique host spectrum. The specific O-antigen residue of E. coli O157:H7 may be a key factor for phage infection by adsorption and receptor identification. The phage exhibited strong antibacterial activity against E. coli O157:H7 over a broad pH range and showed little development of phage-insensitive mutants. The phage sustained viability on the burger patties and reduced E. coli O157:H7 to a non-detectable level without the emergence of resistant cells at low temperatures for five days. Therefore, phage BECP10 might be a good biocontrol agent for E. coli O157:H7-contaminated food matrices.     

Preparation of immunomagnetic iron-dextran nanopartides and application in rapid isolation of E.coli O157:H7 from foods

AIM: To prepare a kind of magnetic iron-dextran nanopartides that was coated with anti-E.coli O157:H7 IgG, analyze its application conditions, and try to use it to isolate E.coli O157:H7 from foods. METHODS: Magnetic iron-dextran nanopartides were prepared by the reaction of a mixture of ferric and ferrous ions with dextran polymers under alkaline conditions. The particles were coated with antiserum against E.coli O157: H7 by the periodate oxidation-borohydride reduction procedure. The oxidation time, amount of antibody coating the particles, amount of nanoparticles, incubation time and isolation time were varied to determine their effects on recovery of the organisms. Finally, the optimum conditions for isolating E.coli O157:H7 from food samples were established. RESULTS: E.coli O157:H7 can be isolated from samples within 15 min with the sensitivity of 101 CFU/mL or even less. In the presence of 108 CFU/mL of other organisms, the sensitivity is 101-102 CFU/mL. Nonspecific binding of other bacteria to the particles was not observed. Two and a half hours of enrichment is enough for the particles to detect the target from the food samples inoculated with 1 CFU/g. CONCLUSION: Isolation of target bacteria by immuno magnetic nanoparticles is an efficient method with high sensitivity and specificity. The technique is so simple that it can be operated in lab and field even by untrained personnel.     

Preparation of immunomagnetic iron-dextran nanoparticles and application in rapid isolation of E.coli O157：H7 from foods

AIM: To prepare a kind of magnetic iron-dextran nanoparticles that was coated with anti-E.coli O157:H7 IgG, analyze its application conditions, and try to use it to isolate E.coli O157:H7 from foods. METHODS: Magnetic iron-dextran nanoparticles were prepared by the reaction of a mixture of ferric and ferrous ions with dextran polymers under alkaline conditions. The particles were coated with antiserum against E.coli O157:H7 by the periodate oxidation-borohydride reduction procedure. The oxidation time, amount of antibody coating the particles, amount of nanoparticles, incubation time and isolation time were varied to determine their effects on recovery of the organisms. Finally, the optimum conditions for isolating E.coli O157:H7 from food samples were established. RESULTS: E.coli O157:H7 can be isolated from samples within 15 min with the sensitivity of 10(1) CFU/mL or even less. In the presence of 10(8) CFU/mL of other organisms, the sensitivity is 10(1)-10(2) CFU/mL. Nonspecific binding of other bacteria to the particles was not observed. Two and a half hours of enrichment is enough for the particles to detect the target from the food samples inoculated with 1 CFU/g. CONCLUSION: Isolation of target bacteria by immunomagnetic nanoparticles is an efficient method with high sensitivity and specificity. The technique is so simple that it can be operated in lab and field even by untrained personnel.     

衢州市带毒力因子肠出血性大肠埃希菌O157：H7的检测

目的了解衢州市家禽、家畜肠出血性大肠埃希菌O157:H7带菌情况和菌型分布特征,以制定相应的防治对策。方法6月份肠道传染病高发季节,采集动物粪便标本,对O157:H7菌株进行分离培养,并用PCR方法检测其毒力基因。结果共采集动物粪便标本300份,检出O157:H7菌16株,总带菌率为5.33%,其中牛、羊、猪带菌率较高,分别为20.83%、12.70%和3.61%。经PCR检测,检出的所有菌株均携带SLT2毒力因子,而SLT1与hly阴性。结论衢州市分离到带有毒力基因的肠出血性大肠埃希菌O157:H7,对人群健康构成了威胁,应加强O157:H7的综合监测。     

非O157产志贺毒素大肠埃希菌研究进展

产志贺毒素大肠埃希菌(Shiga toxin-producing Escherichia coli,STEC)是一类能产生一种或一种以上志贺毒素的大肠埃希菌的总称,包括400余种血清型,其中以O157∶H7血清型为主。近年来,非O157STEC在世界范围内引起散发感染和暴发的报道明显增加,但由于非O157STEC血清型多样,菌株间表型差异较大,目前尚无一种有效的能用于所有非O157STEC菌株分离的方法,因此非O157STEC的流行情况可能被低估。本文就非O157STEC的病原学、致病机制、流行病学特征、实验室诊断、治疗和预防等方面的研究进展做一简要综述。     

上海地区2006-2009年分离的大肠埃希菌O157特征分析研究

目的分析2006年至2009年在上海地区各监测点从病人、动物粪便及食品中分离的13株大肠埃希菌O157（E.coliO157）携带毒力基因的情况,分子分型特征及各菌株之间的相关性。方法利用聚合酶链反应（PCR）和脉冲场凝胶电泳（PFGE）技术,结合生化鉴定、血清学分型的表型分析方法及Vero细胞毒性试验对上海地区分离的13株E.coliO157进行研究。结果 PCR结果显示有9株菌株的菌体抗原基因O157,鞭毛抗原基因H7及毒力基因stx2,hly,eaeA检测结果均为阳性,其中1株食品分离株的stx1基因检测结果也为阳性;9株菌均对Vero细胞有毒性作用。其余4株牛粪分离株,除O157基因检测结果为阳性外,其他检测结果均为阴性。13株上海分离株可分成6个PFGE型别。其中1株食品分离株与同样带有stx1基因的德国分离株的图谱最为接近;2株腹泻病人分离株属于同一PFGE型别;6株牛粪分离株的PFGE型别相同或高度相似。其余4株不携带毒力基因的牛粪分离株为不相关菌株。结论上海地区从病人、动物粪便和食品中都分离获得了能产生stx毒素的E.coliO157,提示需加强对该菌的监测。     

多重PCR方法检测大肠杆菌O157:H7的初步研究

目的研究一种快速、特异的检测大肠杆菌O157：H7的多重PCR方法。方法以大肠杆菌O157：H7的O157抗原基因（rfbE基因）、鞭毛H7抗原基因（fliC基因）、粘附素基因（eaeA基因）和志贺样毒素Ⅰ、Ⅱ（SLT-Ⅰ、SLT-Ⅱ基因）为扩增对象，设计能导至目的片段大小不同的5对引物，通过优化条件，建立了可用于粪便检测的大肠杆菌5重PCR。结果在同一扩增体系中，检测了5株不同来源的大肠杆菌O157：H7及27株非大肠杆菌O157：H7细菌。结果表明，该方法能从2株大肠杆菌O157：H7中扩增出rfbE、fliC、eaeA、SLT-Ⅰ、SLT-Ⅱ基因，它们的大小分别为582bp、802bp、487bp、368bp和177bp。而另外3株大肠杆菌O157：H7也能扩增出除eaeA、SLT-Ⅱ基因外的其它3个基因片段。表明该方法可用于检测大肠杆菌O157：H7，还可检测细菌是否含有毒素基因。在检测27株非大肠杆菌O157：H7．除O149出现SLT-Ⅱ扩增产物和01：H7出现flic基因扩增产物外，其它非大肠杆菌O157：H7的扩增结果均为阴性，表明该方法有较高的特异性。当粪便样品经增菌培养12h，用该5重PCR体系能检测出最初接种量为5cfu／g粪便的样品。结论本5重PCR方法具有较高的特异性和敏感性，可迅速、有效地将大肠杆菌O157：H7与其它非大肠杆菌O157：H7相区别，同时还能检测O157：H7中的毒力因子。因此，通过进一步研究，本方法有望应用于临床大肠杆菌O157：H7感染的辅助诊断。     

Microarray analysis of Escherichia coliO157：H7

AIM: To establish the rapid, specific, and sensitive method for detecting O157:H7 with DNA microchips. METHODS: Specific oligonucleotide probes (26-28 nt) of bacterial antigenic and virulent genes of E. coli O157:H7 and other related pathogen genes were pre-synthesized and immobilized on a solid support to make microchips. The four genes encoding O157 somatic antigen (rfbE), H7 flagellar antigen (fliC) and toxins (SLT1, SLT2) were monitored by multiplex PCR with four pairs of specific primers. Fluorescence-Cy3 labeled samples for hybridization were generated by PCR with Cy3-labeled single prime. Hybridization was performed for 60 min at 45 degrees. Microchip images were taken using a confocal fluorescent scanner. RESULTS: Twelve different bacterial strains were detected with various combinations of four virulent genes. All the O157:H7 strains yielded positive results by multiplex PCR. The size of the PCR products generated with these primers varied from 210 to 678 bp. All the rfbE/fliC/SLT1/SLT2 probes specifically recognized Cy3-labeled fluorescent samples from O157:H7 strains, or strains containing O157 and H7 genes. No cross hybridization of O157:H7 fluorescent samples occurred in other probes. Non-O157:H7 pathogens failed to yield any signal under comparable conditions. If the Cy3-labeled fluorescent product of O157 single PCR was diluted 50-fold, no signal was found in agarose gel electrophoresis, but a positive signal was found in microarray hybridization. CONCLUSION: Microarray analysis of O157:H7 is a rapid, specific, and efficient method for identification and detection of bacterial pathogens.     

浙江省O157大肠杆菌监测及其分子生物学特性

目的了解肠出血性大肠杆菌O157∶H7和其他O157大肠杆菌在浙江省动物、人群中的分布、流行以及PFGE分型、毒力基因携带状况。方法按全国O157∶H7监测方案在5-10月份肠道传染病高发季节,采集全省各地(市)肠道门诊腹泻病人粪便,进行O157大肠杆菌分离培养,并用免疫磁珠分离法对浙江省5个监测点的宿主动物进行O157∶H7分离培养、鉴定,可疑菌株以PCR法检测O157∶H7抗原、志贺样毒素(stx1和stx2)、粘附抹平因子(eaeA)及溶血素(hly)4种毒力基因。用脉冲场凝胶电泳(pulse field gel electrophoresis,PFGE)方法进行同源性分析,同时选择14种抗生素进行药敏试验,并将分析结果与本省首株患者粪便中分离的产志贺样毒素的O157∶H7菌株进行比较。结果全省5个监测点2006年共监测动物粪便标本2377份,分离到4株O157∶H7菌株,阳性率为0.17%;同时在绍兴、舟山肠道门诊腹泻病人粪便中分离到2株O157:H?菌株。4株O157∶H7菌株,stx2、Hly、eaeA均阳性,stx1均阴性;2株O157∶H?菌株仅1株携带eaeA毒力基因。脉冲场凝胶电泳分型显示,4株O157∶H7菌株分3个型,除金华地区2006年分离所得2株完全相似外,其它相同地区不同年代分离的O157∶H7菌株及相同年代不同地区分离的O157∶H7菌株则完全不相似。2株O157∶H?菌株1株PF-GE电泳条带降解,另1株与其它O157∶H7菌株电泳条带差异明显。结论浙江省大肠杆菌0157菌株在动物中以携带stx2毒力基因的O157∶H7菌株为主,但在腹泻患者中则以不带志贺样毒素的O157∶H?菌株为主。不同地区分离的O157∶H7菌株PFGE分型差异明显。羊、奶牛是携带stx2毒力基因的O157∶H7大肠杆菌的主要宿主。各级疾控应加强对宿主动物和腹泻病人大肠杆菌O157的分离监测和流行病学调查。     

肠出血性大肠埃希菌O157:H7Ⅱ型志贺毒素的纯化及功能鉴定

目的 亲和层析纯化肠出血性大肠埃希菌(EHEC)O157:H7Ⅱ型志贺毒素,并鉴定其生物学功能.方法 用抗-Ⅱ型志贺毒素分子A亚单位的抗体S1D8耦联至柱填料Sepharose 4B,制备亲和层析柱.纯化EHEC O157:H7菌体分泌的毒素分子,分别用聚丙烯酰胺凝胶电泳(SDSPAGE)和Western印迹法鉴定毒素分子纯度和特异度,将纯化毒素倍比稀释,观察其对Vero细胞和小鼠的毒性作用,计算其对细胞半数致死量(CD50)和对小鼠的全数致死量(LD100);观察抗毒素血清对小鼠进行毒素攻击的保护作用.结果 通过亲和层析从EHEC O157:H7培养物中成功纯化Ⅱ型志贺毒素.SDS-PAGE显示,其A、B亚单位的相对分子质量分别为32 000和7 500,纯化的毒素分子可分别与Ⅱ型志贺毒素A、B亚单位特异性的单抗结合;对Vero细胞和小鼠均存在致死作用,其CD50和LD100分别为20 ng/L和5 ng,小鼠体内抗毒素血清对毒素可有效中和.结论 成功纯化Ⅱ型志贺毒素,并证实其在细胞和动物模型中的毒性作用.     

广东地区大肠杆菌O157∶H7的分离与鉴定

目的了解广东地区家畜、肉菜市场及屠宰场中动物、动物源性食品原材料中大肠杆菌O157H7的分布及这些细菌对常用抗菌素的敏感性。了解这些细菌对小白鼠的致病力。方法样品采集送实验室后,接种mEC+n肉汤培养基中于41℃增菌24h,取增菌液接种CTSMAC平板,37℃培养24h,挑取可疑菌落,经血清学检验、微量生化实验初步确认。再用5重PCR对它们进行基因检测确认。然后在小白鼠中进行毒性试验;用药敏试纸测试它们对常用抗菌素的敏感性。结果共检查猪、牛粪便、猪肉样品及肝肺拭子样品共774份,检出4株O157H7,检出率052%;对分离菌株作药物试验,发现菌株对四株素,链霉素、青霉素、磺胺类等存在不同程度的耐药。结论我们首次对广东省作O157H7较全面的调查,分离出4株O157H7。     

江苏省肠出血性大肠埃希菌O157的基因PCR-RFLP分型研究

目的对历年从江苏省不同地区分离的肠出血性大肠埃希菌O157（以下简称：O157）进行分型分析。方法采用多聚酶链反应-限制性片段长度多态性分析（PCR-RFLP）方法对108株O157分子分型,比较不同地区、不同年份菌型差异。结果根据EcoRV限制性酶切图谱可将菌株分成JS01-JS10十个不同的型别。主要菌型JS01占64.9%,JS02型与JS01型菌株酶切图谱相似度很高,JS03和JS04型菌株数目较少（12株）,但近一半属于人源菌株。从时间方面看,1999年分离的菌型最多;从地区方面看,铜山县分离到的菌株型别最为多样化。结论不同菌型之间的致病性存在差异,菌株与地理来源的关系密切。PCR-RFLP方法操作简便、重复性好,为O157的流行病学研究提供了一条全新途径。     

Microarray analysis of Escherichia coli0157:H7

AIM: To establish the rapid, specific, and sensitive method for detecting O157:H7 with DNA microchips. METHODS: Specific oligonucleotide probes(26-28 nt) of bacterial antigenic and virulent genes of E.coli O157:H7 and other related pathogen genes were pre-synthesized and immobilized on a solid support to make microchips. The four genes encoding O157 somatic antigen(rfbE), H7 flagellar antigen(fliC)and toxins(SLT1, SLT2) were monitored by multiplex PCR with four pairs of specific primers. Fluorescence-Cy3 labeled samples for hybridization were generated by PCR with Cy3-labeled single prime. Hybridization was performed for 60 min at 45℃. Microchip images were taken using a confocal fluorescent scanner. RESULTS: Twelve different bacterial strains were detected with various combinations of four virulent genes. All the O157:H7 strains yielded positive results by multiplex PCR. The size of the PCR products generated with these primers varied from 210 to 678 bp. All the rfbE/fliC/SLT1/SLT2 probes specifically recognized Cy3-labeled fluorescent samples from O157:H7 strains, or strains containing O157 and H7 genes. No cross hybridization of O157:H7 fluorescent samples occurred in other probes. Non-O157:H7 pathogens failed to yield any signal under comparable conditions. If the Cy3-labeled fluorescent product of O157 single PCR was diluted 50-fold, no signal was found in agarose gel electrophoresis, but a positive signal was found in microarray hybridization. CONCLUSION: Microarray analysis of O157:H7 is a rapid, specific, and efficient method for identification and detection of bacterial pathogens.     

应用多重PCR方法检测大肠埃希菌O157：H8的初步研究

目的 研究一种快速、特异的检测大肠埃希菌（以下称大肠杆菌）O157：H7的复合PCR方法。方法 选用针对大肠杆菌O157：H7志贺样毒素Ⅰ、Ⅱ（SLT-Ⅰ、SLT-Ⅱ）和溶血素（Hly)基因的三对引物,在同一扩增体系中进行PCR,检测12株不同来源的O157：H7大肠杆菌及其它致病性大肠杆菌及沙门菌、志贺菌15株。结果 除质粒缺失株（933）外,其余11株O157：H7大肠杆菌均在361bp处有溶血素基因产物出现;而12株O157：H8大肠杆菌扩增后的两条志贺样毒素基因产物存在差异,其中6株在210bp、484bp处出现两条相应产物,3株仅有210bp一条SLT－Ⅰ基因产物,另3株仅有484bp的SLT－Ⅱ基因产物。其它致病性大肠杆菌及沙门菌、志贺菌的扩增结果均为阴性。结论 本复合PCR方法具有较高的特异性,可迅速、有效地将O157：H7大肠杆菌与其它常见致病性大肠杆菌及沙门菌、志贺菌相鉴别,通过进一步研究有望应用于临床大肠杆菌O157：H7感染的辅助诊断。     

肠出血性大肠杆菌O157：H7L型及其意义的研究

目的诱导肠出血性大肠杆菌O157：H7（以下简称O157：H7）L型观察其特性及意义。方法羧苄青霉素和氨苄青霉素纸片法诱导。比技L型,与原菌生化特性、药物敏感性,L型小鼠灌胃,取肝、结肠、直肠组织分离培养,以观察体内L型存留情况。结果经L型鉴定,如电镜超薄切片等证实细胞壁缺损。L型生化反应比原菌大为减弱、O157凝集为阴性,对抗生素敏感性除卡那霉素（P＜0．01）外,其余同原菌无显著性差别（P＞0．05）。小鼠体内肠道可存留L型,其可回复为细菌型。结论两种抗生素均可诱导O157：H7形成L型。给实验室诊断带来极大困难。提示L型有可能造成该菌感染传播及暴发流行的危险。