多重PCR检测毒力型艰难梭菌的方法学研究及应用

目的建立多重PCR方法检测毒力型艰难梭菌。方法设计艰难梭菌种特异tpi引物和毒力基因tcdA、tcdB特异性引物,建立多重PCR方法。利用已知菌株,验证方法的特异性和最低检出限。与厌氧培养法、ELISA法比较其检测临床菌株和其毒素分泌的准确性。结果多重PCR方法检测艰难梭菌的最低检出浓度为0.7 pg/μ1,特异性为100%。53株厌氧培养法鉴定的艰难梭菌临床分离株,多重PCR方法检测tpi基因均为阳性,其中tcdA+/tcdB+为39株,tcdA-/tcdB-为14株。ELISA法检测毒素A/B显示23株为阳性、30株为阴性。23株ELISA法毒素A/B阳性的艰难梭菌多重PCR方法检测结果均为tcdA+/tcdB+。结论多重PCR方法可用于检测毒力型艰难梭菌具有较高的临床应用价值。     

多重聚合酶链反应检测流感嗜血杆菌

目的 建立检测流感嗜血杆菌的多重聚合酶链反应(M-PCR)方法 .方法 合成扩增流感嗜血杆菌编码P6外膜蛋白基因的引物(Hi),鉴定流感嗜血杆菌种特异性;合成扩增流感嗜血杆菌编码荚膜基因的引物(Hi-cap),鉴定菌株是否具有荚膜;设计并合成6对扩增流感嗜血杆菌不同血清型(荚膜型)编码摹因的引物(Hia-Hif),鉴定菌株的血清型,以其他呼吸道常见病原体菌株做对照,应用M-PCR方法 对200株临床分离的疑似流感嗜血杆菌菌株进行鉴定和血清分型.结果 M-PCR方法 检测流感嗜血杆菌具有高度的敏感性和特异性.对照菌株应用种(Hi)、荚膜(Hi-cap)和荚膜型(Hia-Hif)特异引物没有扩增出DNA片段.M-PCR方法 检测DNA的最低检测量为0.935 Pg.对临床分离的200株疑似流感嗜血杆菌鉴定,189株为流感嗜血杆菌,与API R NH鉴定结果 一致.其中1株具有荚膜,为f血清型,与玻片凝集法鉴定结果 一致.结论 M-PCR方法 检测流感嗜血杆菌具有较高的敏感性和特异性,可用于流感嗜血杆菌感染病例标本的快速检测和病例诊断.     

艰难梭菌感染实验室检测方法进展

<正>艰难梭菌(Clostridium difficile,CD)是一种专性厌氧的革兰阳性芽孢杆菌,1935年首次在新生儿肠道正常菌群中被分离出来。1978年起人们发现该细菌是引起抗生素相关性腹泻、医院性腹泻及假膜性肠炎的主要病原体。有资料显示,25%~30%的抗生素相关性腹泻以及90%以上的假膜性肠炎均是由CD引起的,美国由艰难梭菌感染(Clostridium-difficile infection,CDI)所致的病死     

细菌性脑膜炎多重聚合酶链反应检测方法的研究

目的建立8种细菌性脑膜炎多重聚合酶链反应(Multiplex-polymerase Chain Reaction M-PCR)检测方法。方法针对脑膜炎奈瑟菌、流行性感冒嗜血杆菌、肺炎链球菌、金黄色葡萄球菌、单核细胞增生性李斯特菌、猪链球菌、结核杆菌、新生隐球菌的种特异性基因,通过优化单一PCR扩增体系及扩增程序,建立M-PCR方法检测8种导致细菌性脑膜炎的病原体,检测M-PCR体系的灵敏度。结果初步建立了检测8种导致细菌性脑膜炎病原体的M-PCR扩增方法,能够同时检测多种导致细菌性脑膜炎的病原。结论M-PCR方法较常规的分离培养鉴定方法具有较高的灵敏度和检测快速的特点,适合临床疑似细菌性脑膜炎感染病例的检测及筛查,提高临床细菌性感染脑膜炎病例的诊断阳性率。     

多重逆转录聚合酶链反应检测流感病毒

目的：建立特异敏感的热速检测流感病毒的分子生物学方法。方法：用多重逆转录聚合酶链反应连接多重聚合酶链反应扩增甲1、甲3和乙型流感病毒的HA基因的HA1片段。根据扩增产物的大小检测流感病毒。结果：以流感病毒的HA基因为模板设计的三对引物能特异性地扩增出942bp、1117bp和751bp的核酸片段，它们分别和甲1、甲3和乙型流感病毒有稳定对应关系。根据扩增产物的大小可以检测流感病毒。用这个方法能检测病毒浓度为0．1TCID50的样品。还可以直接从疑似流感病人的含漱液中检测到乙型流感病毒。结论：多重逆转录聚合酶链反应连接多重聚合酶链反应是检测流感病毒的特异敏感的方法，此法还能直接从疑似流感病人的含漱液中检测到乙型流感病毒。     

艰难梭菌谷氨酸脱氢酶抗原及毒素检测试剂盒对艰难梭菌感染诊断价值的Meta分析

目的探讨艰难梭菌谷氨酸脱氢酶(GDH)抗原及毒素检测试剂盒(简称CD快速检测试剂盒)对艰难梭菌感染(CDI)的诊断价值。方法按照纳入和排除标准筛选文献,检索有关CD快速检测试剂盒诊断CDI的文献,采用诊断准确性研究的质量评价工具QUADAS进行质量评价,应用Meta DiSc 1.4软件进行Meta分析。结果共纳入8篇文献2 852例研究对象。纳入文献均为高质量文献,异质性检验显示无阈值效应,但存在其他原因导致的非阈值性异质性。采用随机效应模型进行Meta分析,结果显示,CD快速检测试剂盒GDH抗原检测诊断CDI的合并灵敏度、特异度、阳性似然比、阴性似然比、诊断优势比及其95%CI分别为0.96(0.94,0.98)、0.96(0.95,0.97)、20.07(13.47,29.92)、0.04(0.03,0.07)、409.35(168.01,997.39);毒素检测诊断CDI分别为0.54(0.48,0.59)、1.00(0.99,1.00)、64.23(18.90,218.33)、0.48(0.37,0.62)、142.74(40.94,497.61)。试剂盒GDH抗原、毒素检测诊断CDI的受试者工作曲线下面积(AUCSROC)分别为0.9877、0.9529,Q*指数分别为0.9718、0.9228。结论 CD快速检测试剂盒抗原检测部分灵敏度、特异度、阳性似然比、阴性似然比及诊断优势比均较高,毒素检测部分虽灵敏度欠佳,但特异度较高,可作为缺乏专业设备条件的地区及医院CDI的初筛试剂盒。     

用两种聚合酶链反应方法检测流感病毒

目的：建立特异敏感的快速检测流感病毒的分子生物学方法。方法：用多重逆转录聚合酶链反应和半巢式多重聚合酶链反应扩增甲1、甲3和乙型流感病毒的HA基因的HA1片段。根据扩增产物的大小检测流感病毒。结果：以流感病毒的H基因为模板设计的3对引物能特异性地扩增出942bp,1117bp和751bp的核酸片段，它们分别和甲1，甲3和乙型流感病毒有稳定对应的关系。根据扩增产物的大小可以检测流感病毒。用这个方法能检测病毒浓度为0．1TCID50的样品。结论：多重逆转录聚合酶链反应和半巢式多重聚合酶链反应是检测流感病毒的特异敏感的方法。     

空肠弯曲菌多重聚合酶链反应基因鉴定及其毒力相关基因分析

目的建立空肠弯曲菌、结肠弯曲菌多重聚合酶链反应（m-PCR）鉴定方法,并对菌株毒力相关基因cadF、virB11、flaA、cdtA、cdtB、cdtC的分布进行初步分析。方法利用m-PCR的方法对经过传统生物化学方法鉴定的65株弯曲菌进行鉴定,并通过空肠弯曲菌特异基因hipO、结肠弯曲菌glyA基因特异片段的PCR扩增对鉴定的结果进一步验证;利用特异引物PCR方法初步分析其毒力、毒素相关基因cadF、virB11、flaA、cdtA、cdtB和cdtC的分布。结果m-PCR扩增结果发现65株不同来源的弯曲菌,42株为空肠弯曲菌,23株为结肠弯曲菌。hipO、glyA基因PCR扩增结果与m-PCR扩增结果一致。16．9%菌株PCR鉴定结果与传统的生物化学鉴定结果不一致。100%（65/ 65）菌株cadF、flaA基因阳性,并且PCR扩增片段大小一致。virB的阳性率为10．8%（7/65）,其中空肠弯曲菌阳性率11．9%（5/42）,结肠弯曲菌阳性率为8．7%（2/23）。空肠弯曲菌、结肠弯曲菌cdtA的阳性率分别为100%（42/42）和78%（18/23）;空肠弯曲菌cdtB扩增的的阳性率为97．6%（41/42）。而23株结肠弯曲菌扩增结果均为阴性;空肠弯曲菌、结肠弯曲菌cdtC的阳性率皆为100%,但PCR扩增产物大小不一致,空肠弯曲菌为555 bp,结肠弯曲菌约为465 bp。结论m-PCR的方法可以有效的对空肠弯曲菌和结肠弯曲菌进行属内分型。中国菌株细胞溶涨毒素基因簇cdt基因的特征与文献报道国外菌株存在差异。     

用聚合酶链反应法检测水中产气荚膜梭菌

1980年ＢｉｓｓｏｎＪＷ和ＣａｂｅｌｌｉＶＪ指出[1],产气荚膜梭菌繁殖体的出现表示水受到新近粪便污染,而其芽胞的出现则表明污染为陈旧性的,并提出产气荚膜梭菌作为水污染的指示菌有一定的卫生学意义。但它存在的一个主要缺陷是没有简易、快速、经济的检测方法。为此,我们对检测水中产气荚膜梭菌的聚合酶链反应(ＰＣＲ)方法进行了研究。材料与方法1.菌株来源:产气荚膜梭菌20株(肠毒性产气荚膜梭菌14株;非肠毒性产气荚膜梭菌6株),其中产气荚膜梭菌肠毒株ＮＣＴＣ8239、Ｃ581购于卫生部生物药品鉴定所,其余由西京医院检验科提供。2.主要试…     

学龄前患儿艰难梭菌毒素基因分型及患儿临床特点分析

目的探讨学龄前患儿艰难梭菌毒素基因分型及患儿临床特点。方法选取2017年10月—2020年10月在嘉兴市第二医院儿科住院的148例腹泻患儿为研究对象,所有患儿均留取48 h内粪便,将粪便标本置于-80℃冰箱中,进行艰难梭菌培养,实时荧光定量PCR完成DNA提取及毒素基因检测,酶联免疫吸附法测毒素A/B。结果148例腹泻患者的粪便标本培养出24株艰难梭菌,分离率16.21%。发现粪便标本培养阳性及培养阴性患儿近2个月抗生素使用情况、血红蛋白含量、白蛋白含量及粪便性状差异有统计学意义(P<0.05)。用PCR法对24株艰难梭菌毒素基因检测,tcdA和tcdB均为阳性菌株9株(37.50%),均为阴性3株(12.50%)。tcdA或tcdB阳性有12株(50.00%),其中tcdA^(-)tcdB^(+)菌株9株,tcdA^(+)tcdB^(-)菌株3株。酶联免疫吸附法检测,测得毒素阳性21例,阳性率为87.50%,其中毒素A^(+)B^(-)9例,毒素A^(+)B^(+)6例,毒素A^(-)B^(+)6例。建立logistic回归模型分析,抗生素过去2个月、白蛋白与粪便性状是艰难梭菌感染的危险因素(P<0.05)。结论艰难梭菌培养以产毒株tcdA^(-)tcdB^(+)、A^(+)B^(-)为主,艰难梭菌感染与抗生素过去2个月、白蛋白与粪便性状体有关,为艰难梭菌监测、预防具有指导价值。     

Binary toxin and death after Clostridium difficile infection

We compared 30-day case-fatality rates for patients infected with Clostridium difficile possessing genes for toxins A and B without binary toxin (n = 212) with rates for patients infected with C. difficile possessing genes for A, B, and binary toxin. The latter group comprised patients infected with strains of PCR ribotype 027 (CD027, n = 193) or non-027 (CD non-027, n = 72). Patients with binary toxin had higher case-fatality rates than patients without binary toxin, in univariate analysis (relative risk [RR] 1.8, 95% confidence interval [CI] 1.2-2.7) and multivariate analysis after adjustment for age, sex, and geographic region (RR 1.6, 95% CI 1.0-2.4). Similar case-fatality rates (27.8%, 28.0%) were observed for patients infected with CD027 or CD non-027. Binary toxin either is a marker for more virulent C. difficile strains or contributes directly to strain virulence. Efforts to control C. difficile infection should target all virulent strains irrespective of PCR ribotype.     

Diarrhea due to Clostridium difficile toxin in hemato-oncological patients]

In two patients with multiple myeloma, men aged 72 and 54 years, diarrhoea developed upon chemotherapy with vincristin, doxorubicin and dexamethasone (VAD). In the second patient, diarrhoea developed after subsequent peripheral stem cell mobilisation. Pseudomembranous colitis was seen in the first patient during endoscopy but an enzyme immunoassay of the faeces was false negative for Clostridium difficile enterotoxin. The bacterium was later cultured from stool samples and toxins were detected in a repeated immunoassay. Stool samples of the second patient were positive for C. difficile enterotoxin. For both patients an antibiotic treatment resulted in a rapid recovery. In haemato-oncological patients, diarrhoea is often caused by oncolytic therapy. However, consideration should also be given to C. difficile infection as an alternative cause which is easily treatable.     

Prevalence of Clostridium difficile toxin genes in the feces of veal calves and incidence of ground veal contamination

A study was conducted in two parts to determine the prevalence of toxigenic Clostridium difficile in veal calves and retail meat. The first part of the study focused on the veal production continuum (farm to abattoir). Fifty calves from 4 veal herds (n=200) were followed for 18-22 weeks from the time of arrival on the veal farm to the time of slaughter. Fecal samples were collected from calves every 4-6 weeks. Half of the calves included in the study (n=100) were followed to the abattoir where carcass swabs were collected post slaughter. Fecal samples and carcass swabs were screened for genes encoding C. difficile toxins TcdA, TcdB, and CDT by using real-time polymerase chain reaction (PCR). Carcass swabs were also screened for toxigenic C. difficile by using traditional culture methods. In the second part of the study, ground veal products (n=50 samples) purchased from local grocery stores were examined for toxigenic C. difficile by using real-time PCR and traditional culture methods. Fecal samples from 56 of 200 (28%) calves tested positive for C. difficile toxin genes at least once over the course of the study. Calf age (p=0.011) influenced prevalence of C. difficile toxin genes in calf feces. Toxin genes of C. difficile were detected in one carcass swab by multiplex real-time PCR only. Toxigenic C. difficile was detected by PCR and culture in four (8%) and three (6%) ground veal samples, respectively. The findings of the study reveal that toxigenic C. difficile was most prevalent in veal calves (12%) just before slaughter, although viable toxigenic C. difficile was not recovered from veal carcasses. On the contrary, viable toxigenic C. difficle was recovered from 6% retail meat, thus suggesting that contamination occurs either during or after veal fabrication.     

中国部分地区艰难梭菌PCR 核糖体分型及毒素基因多态性研究

目的了解中国部分地区艰难梭菌聚合酶链反应（PCR） 核糖体型别分布及其A、B毒素基因多态性,为建立适宜中国的艰难梭菌分子检测和分子分型技术提供基础数据,同时在基因水平上为艰难梭菌感染导致的复杂临床表现提供依据。方法对中国3个城市（北京、广州、济南）分离的64株艰难梭菌临床株进行PCR 核糖体分型,并对不同型别的26株代表菌株的A、B毒素基因进行扩增测序。结果64株艰难梭菌中,毒素基因型以A+B+型（45株,70.31%）为主,A-B+型19株（29.69%）。共存在9种PCR 核糖体型别,以017型（21株,32.81%）为主要型别,其次为001型（13株,20.31%）、012型（11株,17.19%）。A-B+菌株中,14株(73.68%)是017型,1株是001型。A、B毒素基因呈现一定的多态性,其中有7种A毒素序列型别（TSTA）,6种B毒素序列型别(TSTB),8种A、B毒素序列型别组合（TSTG）。结论我国部分地区的艰难梭菌可能以PCR 核糖体017型为主,A、B毒素基因在菌株间存在多态性,且核糖体型别与毒素基因多态性间存在相对应的关联。应进一步扩大菌株数量和范围,探寻适合我国的分子检测和分子分型方法,从而帮助医院更好地预防和控制艰难梭菌感染。     

Predicting Clostridium difficile toxin in hospitalized patients with antibiotic-associated diarrhea.

OBJECTIVE: Clostridium difficile infection is implicated in 20%-30% of cases of antibiotic-associated diarrhea. Studying hospitalized patients who received antibiotic therapy and developed diarrhea, our objective was to compare the clinical characteristics of patients who developed C. difficile-associated diarrhea (CDAD) with those of patients with a negative result of a stool assay for C. difficile toxin. METHODS: A prospective study was done with a cohort of 217 hospitalized patients who had received antibiotics and developed diarrhea. Patients with CDAD were defined as patients who had diarrhea and a positive result for C. difficile toxin A/B by an enzyme immunoassay of stool. The variables that yielded a significant difference on univariate analysis between patients with a positive assay result and patients with a negative assay result were entered into a logistic regression model for prediction of C. difficile toxin.Setting. A 900-bed tertiary care medical center. RESULTS: Of 217 patients, 52 (24%) had a positive result of assay for C. difficile toxin A/B in their stool. The logistic regression model included impaired functional capacity, watery diarrhea, use of a proton pump inhibitor, use of a histamine receptor blocker, leukocytosis, and hypoalbuminemia. The area under the receiver operating characteristic curve for the model as a predictor of a positive result for the stool toxin assay was 0.896 (95% confidence interval, 0.661-1.000; P<.001), with 95% specificity and 68% sensitivity. CONCLUSIONS: Our results may help clinicians to predict the risk of CDAD in hospitalized patients with antibiotic-associated diarrhea, to guide careful, specific empirical therapy, and to direct early attention to infection control issues.     

Laboratory-based surveillance for vancomycin-resistant enterococci: utility of screening stool specimens submitted for Clostridium difficile toxin assay.

OBJECTIVE: To study vancomycin-resistant enterococci (VRE) gastrointestinal colonization prevalence in high-risk hospitalized patients and to assess the cost and utility of this laboratory-based surveillance. SETTING: Large university teaching hospital. DESIGN: Quarterly prevalence culture survey of 50 stool specimens submitted for Clostridium difficile toxin A assay from October 1996 through June 1999 (n=526). Screening culture survey of all C difficile-positive stool specimens from July 1998 through June 1999 (n=140). PATIENTS: Specimens for analysis were collected from patients who were admitted to the hospital and who had C difficile toxin A testing ordered. Patient samples were excluded from analysis if they were obtained from patients not hospitalized at UCLA Medical Center, if the C difficile toxin assay result was indeterminate, or if the patient was known to have previous VRE colonization or infection. RESULTS: During quarterly surveillance, VRE was detected in 19.8%, C difficile toxin A in 9.5%, and both VRE and C difficile toxin A in 3.2% of stool specimens submitted for C difficile toxin assay. Patients whose stool specimens were positive for C difficile toxin A were significantly more likely than those whose specimens were negative to have VRE detected (odds ratio, 2.3; 95% confidence interval, 1.2-4.5). Based on these findings, in July 1998, we began routine screening of all C difficile-positive stool specimens for VRE. From July 1998 through June 1999, 58 (41.4%) of 140 patients with C difficile-positive specimens had VRE newly detected in the stool. The combined cost of the two laboratory-based surveillance strategies was approximately $62 per VRE-positive patient identified and $5,800 per year. CONCLUSION: Quarterly surveillance of stool submitted for C difficile assay combined with screening all C difficile-positive stools is a cost-effective and efficient strategy for detecting VRE stool colonization among high-risk hospitalized patients. Such a laboratory-based surveillance should be included as part of a comprehensive program to limit nosocomial VRE transmission.     

TaqMan-MGB探针实时荧光定量PCR联合检测难辨梭菌菌属基因及毒素基因方法学的建立

目的 建立一种简便、快速难辨梭菌菌属鉴定及其毒素基因筛查的荧光定量PCR检测方法。方法 采用TaqMan-MGB探针,通过real-time PCR分析系统,同时检测难辨梭菌菌属基因磷酸丙糖异构酶（Tpi）、A毒素（TcdA）、B毒素（TcdB）及缺失部分基因的A毒素（TcdAT）,从特异度、灵敏度及其抗干扰性等方面评价该方法,并联合全自动酶联荧光免疫系统（VIDAS）检测50 例临床不明原因腹泻病例粪便标本探讨其应用价值。结果 难辨梭菌非产毒株 Tpi 基因（tpi）的检测下限是6×10^-2 CFU/μl,产毒株 tpi、tcdA、tcdB、tcdAT 的检测下限为 6×10^-1 CFU/μl;难辨梭菌非产毒株tpi检测下限批内、批间变异率分别为2.1%和2.3%;产毒株tpi、tcdA、tcdB、tcdAT的检测下限批内、批间变异率依次为3.0%和3.4%、2.9%和3.2%、5.3%和5.7%、2.7%和2.8%。临床常见分离菌株及梭菌属其他细菌对检测无干扰。50 例不明原因腹泻病例粪便标本中,采用TaqMan-MGB 探针实时荧光 PCR 与 VIDAS 酶标免疫检测 39 例阴性标本其符合率为 100%;6 例两方法检测均为阳性;3例VIDAS酶标免疫检测为可疑及2例为阴性,经TaqMan-MGB探针实时荧光PCR检测为A-/B＋菌株。结论 建立的TaqMan-MGB探针实时荧光定量PCR具有高通量、高灵敏度和重复性好的特性,且可筛查携带缺失部分基因的TcdA难辨梭菌菌株。     

Rapid detection of toxigenic Clostridium difficile from stool samples by a nested PCR of toxin B gene

Toxigenic Clostridium difficile is the aetiologic agent of most cases of antibiotic-associated diarrhoea and pseudomembranous colitis. The present standard method for C. difficile diagnosis is a cytotoxicity assay, performed on human fibroblast cultures. It is time consuming and requires special facilities. A nested-PCR assay detecting toxin B gene within a few hours was designed. One hundred and two stool samples were collected during four months. All samples were processed for toxin B-PCR, cultured for C. difficile and tested for cytotoxicity. This approach achieved 99% concordance with the cytotoxic assay. The sensitivity and specificity for the new PCR assay were 96.3% and 100% respectively. The procedure described is easy to perform, does not require special equipment and has produced excellent results. It deserves serious consideration for routine clinical microbiology laboratory use.