艰难梭菌毒素A/B、BD-PCR毒素基因及GDH检测对艰难梭菌相关性腹泻的诊断价值

目的探讨艰难梭菌毒素A/B及其相关毒素基因检测对艰难梭菌相关性腹泻的诊断价值。方法收集2015年1月至2015年10月我院ICU病房腹泻疑似艰难梭菌感染患者的粪便标本133例作为研究对象,分别采用艰难梭菌培养法、CDAB法、PCR毒素基因检测法及艰难梭菌毒素GDH检测法进行检测,以艰难梭菌培养法结果为金标准,计算各方法的诊断指标所包含有的特异度、敏感度、阴性预测值和阳性预测值等。结果本研究收集的133例粪便标本中,经过金标准粪便样本厌氧培养法检出阳性结果 20例,阴性结果 113例。CDAB法具有低敏感度(0.550)和高特异度(0.912),诊断符合率为0.932,BD-PCR毒素基因检测法具有高敏感度(0.950)和高特异度(0.929),诊断符合率为0.932,艰难梭菌毒素GDH检测法的高敏感度(0.900)和低特异度(0.779),诊断符合率为0.797。结论对于疑似艰难梭菌感染,可联合艰难梭菌GDH、艰难梭菌毒素A/B(CDAB)或进行荧光定量PCR毒素基因共同检测,有效降低检测时间,为临床医师及时提供准确的诊断依据,并制定行之有效的治疗措施。     

抗艰难梭菌A毒素单克隆抗体的制备及特性分析

目的 :制备抗艰难梭菌A毒素的单克隆抗体 (mAb)并鉴定其特性。方法 :用纯化的艰难梭菌A毒素免疫BALB/c小鼠 ,将免疫小鼠的脾细胞与骨髓瘤细胞Sp2 / 0融合 ,采用间接ELISA筛选杂交瘤细胞。用ELISA检测mAb腹水的效价、相对亲和力和进行表位分析 ;用Westernblot检测mAb的特异性。结果 :得到 6株杂交瘤细胞株 ,5C10株细胞分泌的mAb为IgG2a ,4B5和 8A1株细胞分泌的mAb为IgG1,其他 3株细胞mAb (2H7、3E9和 6G8)均分泌IgM。中和试验表明 ,所有的mAb均无中和活性。腹水mAb的效价均在 10 -4以上 ,其中mAb 2H7、6G8、5C10、4B5和 8A1具有共同的表位 ,而mAb 3E9识别的位点与其他 5株不同。mAb 8A1和 4B5的相对亲和力>10 5,其他 4株mAb的相对亲和力 >10 4。在非变性条件下 ,PAGE后Westernblot的结果显示 ,6株mAb均可与相对分子质量 (Mr)为 5 5× 10 4的A毒素产生反应 ;而在变性条件下 ,还原与非还原SDS PAGE后Westernblot均显示 ,6株mAb均可与Mr 为 5× 10 4～ 2 4× 10 4的A毒素产生反应。结论 :6株杂交瘤细胞株均能分泌抗艰难梭菌A毒素的特异性mAb ,为艰难梭菌A毒素的研究提供了有利的工具     

牙龈卟啉单胞菌prtH基因分布与多态性研究

目的　分析牙龈卟啉单胞菌 (P .gingivalis)prtH基因的遗传多态性 ,从而了解细菌变异与其对牙周致病作用的相关性。方法　以PCR技术从牙周炎患者口腔中分离的P .gingivalis进行prtH基因扩增 ;采用斑点杂交法 ,以生物素标记prtH基因为探针 ,与以引物B进行PCR扩增为阳性的P .gingivalis基因组DNA杂交 ;对PCR产物进行AluⅠ限制性酶切和DNA测序分析。结果　以prtH基因A、B引物对 14 0株临床分离株进行PCR扩增 ,分别在 76例 (引物A)和 117例 (引物B)出现阳性扩增产物 ,阳性率分别为 5 4 .2 %、84 %。对 34例引物B扩增阳性的P .gingivalisDNA进行点杂交检测 ,阳性吻合率为 82 .4 %。与GenBank中菌株ATCC332 77(U15 2 82 )和W83(L2 74 83)的prtH基因序列相比 ,5株P .gingivalisPCR扩增产物的测序存在着缺失和点突变。结论　在慢性牙周炎患者临床P .gingivalis分离菌株中存在着prtH基因的遗传多态性 ,本实验建立了具有高度敏感性和特异性的PCR检测方法     

多重PCR对金黄色葡萄球菌杀白细胞素基因的检测

目的应用多重PcR检测含Panton-Valentine杀白细胞素（PVL）基因的金黄色葡萄球菌。方法收集我院2005年1月至2006年1月从临床多种标本中分离的金黄色葡萄球菌，用多重PCR同时检测葡萄球菌16SrRNA基因、mecA基因和lukS/F-PV基因。多重PCR检测MRSA的SCCmec基因型及亚型。结果195株金黄色葡萄球菌经多重PCR检测，121株为耐甲氧西林金黄色葡萄球菌（MRSA），74株为甲氧西林敏感金黄色葡萄球菌（MSSA），共检测到26株金黄色葡萄球菌lukS/F-PV基因阳性，阳性率为13．3％（26，195）。其中19株为MRSA，阳性率为15．7％（19／121）；7株为MSSA，阳性率为12．2％（7／74）。19株lukS/F-PV基因阳性的MRSA的SCCmec基因型分别为SCCmec Ⅲ型10株、SCCmecⅢA型4株、SCCmecⅣ型4株及SCCmecⅠ型1株。26株lukS/F-PV基因阳性的分离株有11株分离自脓液或创面分泌物，10株分离自痰标本，3株分离自血液标本，2株分离自尿液。结论在温州地区分离的MRSA和MSSA中都能检测到Panton-Valentine杀白细胞素基因，含Panton-Valentine杀白细胞素基因MRSA的SCCmec基因型主要为SCCmec Ⅲ，含PVL基因的金黄色葡萄球菌主要引起化脓性感染和肺部感染。     

三种检测常见碳青霉烯酶型方法的评估研究

目的评估mCIM联合eCIM试验、Carba-5和Carba-R三种方法检测碳青霉烯类耐药细菌(carbapenem-resistant organisms, CRO)中常见碳青霉烯酶型的性能。方法随机挑选2019年1月至2020年12月浙江大学医学院附属邵逸夫医院临床分离的122株非重复CRO菌株, 应用生物梅里埃MALDI-TOF MS全自动快速质谱仪对菌株进行菌种鉴定, 分别采用改良碳青霉烯类抗生素灭活试验(mCIM联合eCIM试验)、Carba-5检测条和Carba-R试剂盒对所有菌株进行碳青霉烯酶型检测;以PCR法检测结果为金标准, 评价上述3种检测方法的性能。结果 122株CRO菌株属于12个不同菌种, PCR法碳青霉烯酶型检测结果:共112株检测结果阳性, KPC-2型阳性70株, 占57%(70/122), 其中肺炎克雷伯菌46株, 铜绿假单胞菌12株, 其他菌株12株;OXA-232型阳性19株占15%(19/122), 均为肺炎克雷伯菌;NDM型阳性20株占16%(20/122), 其中NDM-1型阳性7株和NDM-5型阳性13株, 以大肠埃希菌为主(12/20);...     

淋病奈瑟菌临床菌株PⅠ基因型及PⅠB基因点突变分析

目的分析浙江地区淋病奈瑟菌株外膜孔蛋白PⅠ基因序列及其点突变与耐药性关系，了解本地区淋病奈瑟菌株PⅠA与PⅠB基因分布及其优势基因型。方法采用高保真PCR扩增34株淋病奈瑟菌全长PⅠ基因序列，T-A克隆后测序。根据测序结果，建立多重PCR同时检测113株淋病奈瑟菌PⅠA和PⅠB基因。分析测序菌株PⅠB基因中与耐药性密切相关的G120和A121变异情况，采用二倍琼脂稀释法确定PⅠB菌株的耐药性。结果11株PⅠA^＋淋病奈瑟菌均为ⅠA6血清型。23株PⅠB^＋淋病奈瑟菌中，6株（26．1％）为ⅠB3血清型、5株（21．7％）为ⅠB3／6血清型、2株（8．7％）为ⅠB4血清型、9株（39．1％）为ⅠB3／6-ⅠB2嵌合血清型、1株（4．3％）为ⅠB2-ⅠB4嵌合血清型。所建立的多重PCR可特异和准确地对PⅠA和PⅠB基因分型，检测灵敏度为10雌DNA模板。113株淋病奈瑟菌中，26株（23．0％）和87株（77．0％）分别携带PⅠA和PⅠB基因。经测序的23株PⅠB^＋淋病奈瑟菌中，1株（4．3％）G120和A121均未突变，3株（13．0％）G120或A121突变，2株、8．7％）G120突变但A121缺失，17株（73．9％）双位点突变。22株G120和／或A121突变的PⅠB^＋菌株均对青霉素和四环素耐药。结论所建立的多重PCR可用于淋病奈瑟菌PⅠA和PⅠB基因的分型检测。本地区流行的淋病奈瑟菌主要携带PⅠB基因。ⅠA6为PⅠA菌株优势血清型。PⅠB菌株以ⅠB3／6-ⅠB2嵌合、ⅠB3和ⅠB3／6血清型常见，但主要为耐药性G120和／或A121突变株。     

耐甲氧西林金黄色葡萄球菌SCCmec基因分型及药敏分析

目的 研究临床分离的耐甲氧西林金黄色葡萄球菌(MRSA)的SCCmec基因型及亚型并对其耐药性进行分析,为临床治疗和流行病学研究提供依据.方法 应用PCR法检测50株MRSAmeeA基因和SCCmec的基因型及亚型.用纸片扩散法进行药敏试验.结果 50株MESA mecA基因均为阳性.45株为SCCmecⅡ型,3株为SCCmecⅢA型,2株为SCCmec Ⅱ型.未见SCCmee Ⅰ和SCCmecⅣ型.携带SCCmecⅡ、SCCmecⅢ或SCCmecⅢA的菌株均为多重耐药株.结论 50株MESA为多重耐药菌株,以SCCmecⅢ型为主.     

慢性牙周炎患者龈下菌斑中伴放线放线杆菌基因型的分析

目的：建立龈下菌斑标本中伴放线放线杆菌（Actinobacillus actinomycetemcomitans，Aa）PCR检测方法，了解慢性牙周炎患者不同牙位的龈下菌斑中Aα 的感染率及其优势基因型。方法：61例慢性牙周炎患者每例采取2个不同牙位共122份龈下菌斑标本，采用培养法分离Aα菌株，以PCR或多重PCR检测16SrDNA基因、lktA基因和fap基因，部分扩增产物克隆后测序。结果：在11例患者的11份龈下菌斑标本中分离到Aα菌株。122份龈下菌斑中Aα16SrDNA、lktA、和fap检测阳性率分别为84.4%、75.4%、和50.0%。38.8%的患者（19/49）不同牙位龈下菌斑中检出的Aα基因型不一致。Aα有4种基因型，其优势基因型是16SrDNA^ /lktA^ /fap^ ，其次为16SrDNA^ /lktA^ /fap^-。部分标本上述3种基因的扩增片段与文献报道核苷酸序列的同源性为93.75%-100%。结论：建立的PCR或多重PCR有较高的敏感性和特异性，适用于龈下菌斑标本中Aα的快速检测。慢性牙周炎患者Aα感染率较高，并存在优势基因型，部分患者可被不同基因型的菌株同时感染。     

B型流感病毒Yamagata系和Victoria系双重荧光PCR诊断方法的建立与应用

目的 建立一种新型的双重荧光PCR诊断方法,用于B型流感病毒By (B/Yamagata)和Bv(B/Victoria)亚系的准确分子分型.方法 从GenBank随机下载By和By HA(hemagglutinin)基因各50条序列,通过MEGA分析,利用Primer Primer软件设计亚系特异性引物和通用探针,建立双重荧光PCR诊断方法.用HAI(hemagglutination inhibition)实验确认的B型流感病毒亚系分离毒株和A型流感病毒进行特异性验证,用体外转录核酸拷贝数进行灵敏度实验.结果 2006-2010流感监测年份,对17 765份流感样病例咽拭标本中分离到B型流感病毒793株,本方法鉴定有152株By和641株Bv病毒,与HAI鉴定结果一致.本诊断方法的检测特异性达100％,灵敏度达102拷贝/μl,重复性变异系数＜3.5％.结论 本研究所建立的荧光PCR方法为流感实时监测提供了有力的技术支撑,适合于流感监测实验室对流感病毒的快速分子诊断.     

B型肉毒神经毒素基因的PCR检测

本研究用一对Ｂ型肉毒神经毒素基因特异的寡核苷酸引物，扩增Ｂ型基因轻链区域一段２５３ｂｐ的ＤＮＡ片段，对２２株Ｂ型肉毒梭菌进行了鉴定，所试２２株Ｂ型肉毒梭菌其ＰＣＲ均为阳性。用Ｂ型肉毒梭菌ＣＭＣＣ（Ｂ）６４３５２对ＰＣＲ的检测灵敏度进行检查，可从６０个细菌中得到明显的扩增产物。用其它各型肉毒梭菌及其它梭状芽胞杆菌共５３株对ＰＣＲ的特异性进行了检测，除一株Ａ型肉毒梭菌（ＬＣＬ００１）ＰＣＲ为阳性外，其余菌株均为阴性。ＬＣＬ００１的扩增产物其分子量以及限制性内切酶消化产物和Ｂ型肉毒梭菌的扩增产物完全一致，认为该株菌中带有不表达的Ｂ型肉毒神经毒素基因，应为Ａ（Ｂ）型。由此可见，该ＰＣＲ扩增系统不仅具有灵敏度高，特异性强等特点，而且可检测出不表达的Ｂ型肉毒神经毒素基因，用于肉毒梭菌的鉴定具有其它方法不可比拟的优点。     

Multiplex PCR method for detection of Clostridium difficile tcdA, tcdB, cdtA, and cdtB and internal in-frame deletion of tcdC

A multiplex PCR method was developed for the detection of Clostridium difficile toxin genes tcdA, tcdB, ctdA, and cdtB and the major in-frame deletion types (18, 39, and 54 bp) of tcdC. The method has high specificity for PCR ribotype 027 and may identify other C. difficile strains of clinical and epidemiological importance.     

Rapid stool-based diagnosis of Clostridium difficile infection by real-time PCR in a children's hospital

Clostridium difficile is a major cause of nosocomial antibiotic-associated infectious diarrhea and pseudomembranous colitis. Detection of C. difficile by anaerobic bacterial culture and/or cytotoxicity assays has been largely replaced by rapid enzyme immunoassays (EIA). However, due to the lack of sensitivity of stool EIA, we developed a multiplex real-time PCR assay targeting the C. difficile toxin genes tcdA and tcdB. Stool samples from hospitalized pediatric patients suspected of having C. difficile-associated disease were prospectively cultured on cycloserine-cefoxitin-fructose agar following alcohol shock. Six testing modalities were evaluated, including stool EIA, culture EIA, and real-time PCR (tcdA and tcdB) of cultured isolates and stool samples. Real-time PCR detection was performed with tcdA and tcdB gene-specific primers and hydrolysis probes using the LightCycler platforms (Roche Diagnostics, Indianapolis, IN). A total of 157 samples from 96 pediatric patients were analyzed. The sensitivities of stool real-time PCR and stool EIA were 95% and 35%, respectively, with a specificity of 100% for both methods. The lower limit of detection of the stool real-time PCR was 30 CFU/ml of stool sample per reaction for tcdA and tcdB. This study highlights the poor performance of stool toxin EIAs in pediatric settings. Direct detection of C. difficile toxin genes in stool samples by real-time PCR showed sensitivity superior to that of stool and culture EIAs and performance comparable to that of real-time PCR assay of cultured isolates. Real-time PCR of DNA from stool samples is a rapid and cost-effective diagnostic modality for children that should facilitate appropriate patient management and halt the practice of serial testing by EIA.     

Rapid detection of Clostridium difficile in feces by real-time PCR

Clostridium difficile is the major causative agent of nosocomial antibiotic-associated diarrhea, colitis, and pseudomembranous colitis. The pathogenicity of C. difficile is closely related to the production of toxins A and B. Toxigenic C. difficile detection by a tissue culture cytotoxin assay is often considered the "gold standard." However, this assay is time consuming, as it implies an incubation period of at least 24 h. We have developed a rapid real-time fluorescence-based multiplex PCR assay targeting the C. difficile toxin genes tcdA and tcdB, with the Smart Cycler. Two molecular beacons bearing different fluorophores were used as internal probes specific for each amplicon type. The analytical sensitivity of the assay was around 10 genome copies for all nine C. difficile strains tested, representing the 6 most common toxinotypes. The specificity was demonstrated by the absence of amplification with DNA purified from bacterial species other than C. difficile (n = 14), including Clostridium sordellii for which the lethal toxin gene sequence is closely related to the toxin genes of C. difficile. Following a rapid (15 min) and simple fecal sample preparation protocol, both tcdA and tcdB were efficiently amplified from 28 of 29 cytotoxin-positive feces samples. There was no amplification observed with all 27 cytotoxin-negative feces samples tested. This is the first real-time PCR assay for the detection of C. difficile. It is rapid, sensitive, and specific and allows detection of C. difficile directly from feces samples.     

Epidemiology of Clostridium difficile infection in a large teaching hospital in Singapore

AIMS: We undertook this study to define the incidence of toxigenic Clostridium difficile in our hospital and to characterise the isolates. METHODS: All unformed stool was tested for the presence of Toxin A (TcdA) and Toxin B (TcdB), and cultured for C. difficile. Culture filtrates were also tested for TcdA and TcdB. Detection of tcdA and tcdB genes was carried out for A(-)B(+) strains by polymerase chain reaction (PCR).The minimum inhibitory concentrations (MICs) of metronidazole, vancomycin and clindamycin for all isolates were tested using the Etest. PCR ribotyping was carried out on all isolates. RESULTS: The incidence of Clostridium difficile associated disease (CDAD) was 3.2 cases per 1000 admissions or discharges and 53.8 cases per 100 000 patient days. Most cases occurred in renal and haematology patients. CDAD was more common in patients aged over 50 years and of male gender. The Indian population was under-represented. Fourteen (11.8%) isolates were A(-)B(+). All strains were susceptible to metronidazole but one strain showed intermediate resistance to vancomycin. Only 12.8% of the isolates were susceptible to clindamycin. Thirty-five isolates had PCR ribotype A, of which 29 (83%) had a clindamycin MIC >256 mg/L. Thirty-three had PCR ribotype B, of which only one (3%) had a clindamycin MIC >256 mg/L. The 14 A(-)B(+) strains were all PCR ribotype C, and had a range of MICs for clindamycin from 2 to >256 mg/L. CONCLUSIONS: The incidence of CDAD in our hospital is relatively low. Isolates remain susceptible to metronidazole and vancomycin.     

Toxin gene analysis of a variant strain of Clostridium difficile that causes human clinical disease

A toxin variant strain of Clostridium difficile was isolated from two patients with C. difficile-associated disease (CDAD), one of whom died from extensive pseudomembranous colitis. This strain, identified by restriction endonuclease analysis (REA) as type CF2, was not detected by an immunoassay for C. difficile toxin A. Culture supernatants of CF2 failed to elicit significant enterotoxic activity in the rabbit ileal loop assay but did produce atypical cytopathic effects in cell culture assay. Southern hybridization, PCR amplification, and DNA sequence analyses were performed on the toxin A (tcdA) and toxin B (tcdB) genes of type CF2 isolate 5340. Type CF2 5340 tcdA exhibited a 1,821-bp truncation, due to three deletions in the 3' end of the gene, and a point mutation in the 5' end of the gene, resulting in a premature stop codon at tcdA position 139. Type CF2 5340 tcdB exhibited multiple nucleotide base substitutions in the 5' end of the gene compared to tcdB of the standard toxigenic strain VPI 10463. Type CF2 5340 toxin gene nucleotide sequences and deduced amino acid sequences showed a strong resemblance to those of the previously described variant C. difficile strain 1470, a strain reported to have reduced pathogenicity and no association with clinical illness in humans. REA of strain 1470 identified this strain as a distinct type (CF1) within the same REA group as the closely related type CF2. A review of our clinical-isolate collection identified five additional patients infected with type CF2, three of whom had documented CDAD. PCR amplification of the 3' end of tcdA demonstrated identical 1. 8-kb deletions in all seven type CF2 isolates. REA type CF2 is a toxin variant strain of C. difficile that retains the ability to cause disease in humans but is not detected in clinical immunoassays for toxin A.     

Isolation and characterisation of toxin A-negative, toxin B-positive Clostridium difficile in Dublin, Ireland

Clostridium difficile is a major cause of infectious diarrhoea in hospitalised patients. Most pathogenic C. difficile strains produce two toxins, A and B; however, clinically relevant toxin A-negative, toxin B-positive (A- B+) strains of C. difficile that cause diarrhoea and colitis in humans have been isolated worldwide. The aims of this study were to isolate and characterise A- B+ strains from two university hospitals in Dublin, Ireland. Samples positive for C. difficile were identified daily by review of ELISA results and were cultured on selective media. Following culture, toxin-specific immunoassays, IMR-90 cytotoxicity assays and PCR were used to analyse consecutive C. difficile isolates from 93 patients. Using a toxin A-specific ELISA, 52 samples produced detectable toxin. All isolates were positive using a toxin A/B ELISA. Similarly, all isolates were positive with the cytoxicity assay, although variant cytopathic effects were observed in 41 cases. PCR amplification of the toxin A and toxin B genes revealed that 41 of the previous A- B+ strains had a c. 1.7-kb deletion in the 3'-end of the tcdA gene. Restriction enzyme analysis of these amplicons revealed the loss of polymorphic restriction sites. These 41 A- B+ isolates were designated toxinotype VIII by comparison with C. difficile strain 1470. PCR ribotyping revealed that all A- B+ isolates belonged to PCR-ribotype 017. A- B+ C. difficile isolates accounted for 44% of the isolates examined in this study, and appeared to be isolated more frequently in Dublin, Ireland, than reported rates for other countries.     

Characterization of toxin A-negative, toxin B-positive Clostridium difficile isolates from outbreaks in different countries by amplified fragment length polymorphism and PCR ribotyping

Clinical Clostridium difficile isolates of patients with diarrhea or pseudomembranous colitis usually produce both toxin A and toxin B, but an increasing number of reports mention infections due to toxin A-negative, toxin B-positive (A(-)/B(+)) strains. Thirty-nine clinical toxin A(-)/B(+) isolates, and 12 other unrelated isolates were obtained from Canada, the United States, Poland, the United Kingdom, France, Japan, and The Netherlands. The isolates were investigated by high-resolution genetic fingerprinting by use of amplified fragment length polymorphism (AFLP) and two well-described PCR ribotyping methods. Furthermore, the toxin profile and clindamycin resistance were determined. Reference strains of C. difficile representing 30 known serogroups were also included in the analysis. AFLP discriminated 29 types among the reference strains, whereas the two PCR ribotyping methods distinguished 25 and 26 types. The discriminatory power of AFLP and PCR ribotyping among 12 different unrelated isolates was similar. Typing of 39 toxin A(-)/B(+) isolates revealed 2 AFLP types and 2 and 3 PCR ribotypes. Of 39 toxin A(-)/B(+) isolates, 37 had PCR ribotype 017/20 and AFLP type 20 (95%). A deletion of 1.8 kb was seen in 38 isolates, and 1 isolate had a deletion of approximately 1.7 kb in the tcdA gene, which encodes toxin A. Clindamycin resistance encoded by the erm(B) gene was found in 33 of 39 toxin A(-)/B(+) isolates, and in 2 of the 12 unrelated isolates (P < 0.001, chi-square test). We conclude that clindamycin-resistant C. difficile toxin A(-)/B(+) strain (PCR ribotype 017/20, AFLP type 20, serogroup F) has a clonal worldwide spread.     

Antimicrobial resistance, toxinotype, and genotypic profiling of Clostridium difficile isolates of swine origin

The occurrence of Clostridium difficile infections in patients that do not fulfill the classical risk factors prompted us to investigate new risk factors of disease. The goal of this study was to characterize strains and associated antimicrobial resistance determinants of C. difficile isolated from swine raised in Ohio and North Carolina. Genotypic approaches used include PCR detection, toxinotyping, DNA sequencing, and pulsed-field gel electrophoresis (PFGE) DNA fingerprinting. Thirty-one percent (37/119) of isolates carried both tetM and tetW genes. The ermB gene was found in 91% of isolates that were resistant to erythromycin (68/75). Eighty-five percent (521/609) of isolates were toxin gene tcdB and tcdA positive. A total of 81% (494/609) of isolates were positive for cdtB and carry a tcdC gene (a toxin gene negative regulator) with a 39-bp deletion. Overall, 88% (196/223) of pigs carry a single C. difficile strain, while 12% (27/223) of pigs carried multiple strains. To the best of our knowledge, this is the first report of individual pigs found to carry more than one strain type of C. difficile. A significant difference in toxinotype profiles in the two geographic locations was noted, with a significantly (P < 0.001) higher prevalence of toxinotype V found in North Carolina (84%; 189/224) than in Ohio (55%; 99/181). Overall, the study findings indicate that significant proportions of C. difficile in swine are toxigenic and often are associated with antimicrobial resistance genes, although they are not resistant to drugs that are used to treat C. difficile infections.     

Community-acquired Clostridium difficile diarrhea caused by binary toxin, toxin A, and toxin B gene-positive isolates in Hungary

The aim of this work was to study the toxin types of Clostridium difficile isolates originating from different parts of Hungary. A PCR method was used for amplification of the two major toxin genes and the binary toxin gene and to detect the deletion or insertion in the 3' end of the toxin A gene. The findings were compared with the results of cytotoxicity assays on the HeLa cell line. One hundred twelve isolates were tested; the toxin A and toxin B genes were detected in 79 strains by the PCR method. All of the isolates that were positive by the PCR method were also positive by the cytotoxicity assay. All of the other strains (n = 33) were negative for the toxin A and toxin B genes; in these cases, cytopathic effects on the cell line were not observed. No tcdA-negative and tcdB-positive isolates were found by the PCR method. In two cases, the presence of a binary toxin gene was observed by PCR; both isolates that were isolated from diarrheal feces carried the tcdA and tcdB genes. No prior hospitalization had occurred in either case.     

Multilocus sequence typing analysis of human and animal Clostridium difficile isolates of various toxigenic types

A multilocus sequence typing (MLST) scheme was developed to study the genetic relationships and population structure of 72 Clostridium difficile isolates from various hosts, geographic sources, PCR ribotypes, and toxigenic types (determined by PCR targeting tcdA and tcdB genes). MLST was performed by DNA sequence analysis of seven housekeeping genes (aroE, ddl, dutA, tpi, recA, gmk, and sodA). The number of alleles ranged from five (dutA and ddl) to eleven (recA). Allelic profiles allowed the definition of 34 different sequence types (STs). These STs lacked correlation with geographic source but were well correlated to toxigenic type. The dendrogram generated from a matrix of pairwise genetic distances showed that animal isolates did not constitute a distinct lineage from human isolates and that there was no hypervirulent lineage within the population of toxigenic human isolates (isolates recovered from pseudomembranous colitis and antibiotic-associated diarrhea did not cluster in distinct lineages). However, A(-) B(+) variant isolates shared the same ST that appeared as a divergent lineage in the population studied, indicating a single evolutionary origin. The population structure was further examined by analysis of allelic polymorphism. The dendrogram generated from composite sequence-based analysis revealed a homogeneous population associated with three divergent lineages, one of which was restricted to A(-) B(+) variant isolates. C. difficile exhibited a clonal population structure, as revealed by the estimation of linkage disequilibrium (Ia) between loci. The analysis of alleles within clonal complexes estimated that point mutation generated new alleles at a frequency eightfold higher than recombinational exchange, and the congruence of the dendrograms generated from separate housekeeping loci confirmed the mutational evolution of this species.