产气荚膜梭菌肠毒素的致病机理研究进展

产气荚膜梭菌是一种重要的人兽共患病的病原体，可引起人的食物中毒和抗生素相关腹泻，产气荚膜梭菌肠毒素是该菌的一个非常重要的致病毒素，在引起人的胃肠疾病方面起着关键性的作用，本文对产气荚膜梭菌肠毒素产生、细胞毒性和组织学作用以及在胃肠粘膜上造成损伤的致病分子机理等方面的研究内容进行论述。     

产气荚膜梭茵肠毒素的分子生物学研究进展

产气荚膜梭茵（Clostridium perfringens）是一种重要的人兽共患病的病原体，它是一类革兰氏阳性产芽孢的厌氧梭茵，可引起人的食物中毒和肠毒素相关腹泻。近年来，研究人员发现由产气荚膜梭茵导致腹泻的主要原因与该茵在芽孢形成过程中产生的一种肠毒素有关。文章重点针对产气荚膜梭茵肠毒素的生物学特性和致病机制等方面的研究做一综述。     

全面认识家禽腐败皮炎

腐败皮炎（GD）是一种鸡和火鸡的细菌疾病，主要影响腹部皮肤以及皮肤下的组织。GD被认为是芽孢杆菌，通常是产气英膜梭菌或者败毒梭菌引起，但是也有很多其它的细菌从GD损伤的地方分离出来。     

应用随机扩增多态性DNA技术对产气荚腊梭菌的基因分型

采用随机扩增多态性ＤＮＡ（ｒａｎｄｏｍｌｙ ａｍｐｌｉｅｄ ｐｏｌｙｍｏｒｐｈｉｃＤＮＡ,ＲＡＰＤ）技术对产气英膜梭菌进行ＰＣＲ扩菌。结果,产气英膜梭菌Ａ、Ｂ、Ｃ、Ｄ４个型均可扩增出约４３０ｂｐ的条带,Ｂ、Ｃ型还扩增出约２１０ｂｐ的条带,Ｂ、Ｄ型还扩增出约１２１０ｂｐ的条带,Ａ型还扩增出约２４０ｂｐ和６９０ｂｐ的条带,各型之间的条带差别明显。     

产气荚膜梭菌感染肉鸡后宿主免疫反应的机制

坏死性肠炎是一种由产气荚膜梭菌引起的疾病，它威胁着缺乏饲用抗生素情况下的家禽生产。加拿大圭尔夫食品研究中心的科学家采用添加产气荚膜梭菌的饲料饲喂罗斯肉鸡，利用低密度鸡免疫微阵列研究其对产气英膜梭菌感染反应的基因表达谱。共使用24个阵列。包含处理、时间、数纽、随机效应、染色的混合模型以及处理和时间中的所有互作来识别感染后vs感染前之间、感染过程中、     

梅花鹿“猝死症”病原的分离鉴定及药敏试验

对某梅花鹿养殖场送检的猝死鹿进行剖检和病原分离、鉴定及药敏试验.共分离得到2种纯培养细菌,一种为革兰阳性的粗大杆菌,无芽胞,有英膜,溶血;另一种为革兰阴性短杆菌,两极浓染.经生化鉴定表明,分离菌分别是产气英膜梭菌和多杀性巴氏杆菌,并通过药敏试验筛选到2种高度敏感药物.     

产气荚膜梭菌cpe~+菌株的筛选与鉴定

参考相关资料,针对产气荚膜梭菌肠毒素基因(cpe)设计合成1对特异性引物,对34株贵州分离株进行PCR扩增,并将扩增产物连接到pMD18-T载体,转化至大肠杆菌DH5α感受态细胞,提取质粒进行PCR和双酶切鉴定后测序和分析。结果在34株产气荚膜梭菌贵州分离株中有1株C型菌株扩增出与预期大小相一致的目的片段,经克隆测序后,该片段大小为233 bp,其与产气荚膜梭菌参考株肠毒素基因序列的核苷酸同源性为99.6%~100%,推导氨基酸同源性为98.7%~100%,表明所扩增产物为产气荚膜梭菌的肠毒素基因片段。本试验筛选鉴定出1株产气荚膜梭菌cpe+菌株,为今后进一步探讨产气荚膜梭菌性食物中毒机制奠定了基础。     

采用多位点测序分型鉴别肉鸡坏死性肠炎病原

产气英膜梭菌是一种重要的人兽共患病病原体,是家禽坏死性肠炎的重要病原体。加拿大圭尔夫大学、加拿大公共卫生署联合Nutreco公司采用多位点测序分型技术（MLST,一种以核苷酸序列为基础的病原菌分型方法,是高通量测序技术与成熟的群体遗传学相结合的产物）对从暴发坏死性肠炎的肉鸡中分离的61株产气荚膜梭菌进行分型。采用从健康鸡群体内分离的产气英膜梭菌作为对照。     

不同来源产气荚膜梭菌分离株的分子和表型特征

由于欧盟减少使用促进生长的抗生素，诱发肠炎和亚临床疾病的产气英膜梭菌成为禽类健康的重要威胁。比利时科研人员研究了来自不同健康状况的禽群产气英膜梭菌分离株的基因型和表现型特征。健康禽群用泄殖腔拭子取样，感染坏死性肠炎的禽群从肠道和肝脏取样。从23群无临床症状的禽群得到27个分离株，从8个出现临床症状的禽群分离到36个细菌株。采用脉冲凝胶电泳法分型，结果显示来自不同禽群的分离株之间存在高度的基因差异性。所有分离株都属于A型毒素株。5／35个脉冲凝胶电泳样品的分离株包含cpb2基因，编码β-2毒素，2／35的分离株包含cpe基因编码肠毒素。采用ELISA体外定量分离株的α毒素产量，结果表明病群分离株的α毒素产量高于健康群分离株。     

魏氏梭菌肠毒素研究进展

魏氏梭菌是一种重要的人兽共患病的病原体,可引起人的食物中毒和抗生素相关性腹泻(非食源性胃肠道疾病),肠毒素是该菌的一个非常重要的致病毒素,在引起人的胃肠疾病方面起着关键性的作用,作者针对魏氏梭菌肠毒素的生物学特性及分子生物学等方面的研究内容进行论述.     

几例新型仔猪腹泻的诊治

试验旨在对近来多省份流行的仔猪腹泻病原菌进行分离及鉴定,并研究其防治方法。通过临床症状观察、病理解剖、病原菌分离、镜检、菌落形态观察、生化鉴定、动物试验等方法对该病进行综合研究。从多个发病养殖场的腹泻仔猪病变部位分离到一株魏氏梭菌,并探索了其防治方法。结果表明,当前发生的严重仔猪腹泻与感染魏氏梭菌密切相关,采用治疗魏氏梭菌病的方法对该病进行治疗及利用灭活自场疫苗对其预防效果均明显。     

Diarrhea associated with enterotoxigenic Clostridium perfringens in a red-footed tortoise (Geochelone carbonaria).

Enterotoxigenic Clostridium perfringens was associated with diarrhea in a 4-yr-old female captive-bred red-footed tortoise (Geochelone carbonaria). Diagnosis was based on bacterial culture, detection of C. perfringens enterotoxin in feces, and exclusion of commonly recognized pathogens. After treatment with metronidazole, normal feces were passed and C. perfringens enterotoxin was no longer detected in the feces. Although the role of C. perfringens cannot be determined definitively from this case, this pathogen should be considered in cases of diarrhea in tortoises and, perhaps, other reptiles.     

Epizootiologic investigations of a diarrheic syndrome in fattening pigs

A diarrheic syndrome linked to Clostridium perfringens was observed in fattening pigs. A good correlation was observed between the onset and the severity of diarrhea and the fecal passage of C perfringens enterotoxin. Intestinal fluids from affected pigs had activity comparable with that detected in a purified C perfringens enterotoxin. Seven pigs excreting enterotoxin were shown to develop serum antibodies to C perfringens enterotoxin.     

Genotypic and phenotypic characterization of Clostridium perfringens and Clostridium difficile in diarrheic and healthy dogs

The objectives of this study were to examine the potential roles of Clostridium difficile and enterotoxigenic Clostridium perfringens in diarrhea in dogs by comparison of isolation, determination of toxin status via enzyme-linked immunosorbent assay (ELISA), and application of multiplex polymerase chain reaction (PCR). These techniques were used to evaluate fecal specimens in 132 healthy and diarrheic dogs. These dogs were prospectively evaluated by grouping them into the following 3 categories: hospitalized dogs with diarrhea (n = 32), hospitalized dogs without diarrhea (n = 42), and apparently healthy outpatient dogs without diarrhea (n = 58). All fecal specimens were cultured using selective media for C difficile, Salmonella spp., and Campylobacter spp. and selective media after heat shock for C perfringens. No significant difference was found in the isolation of C perfringens or C difficile among the 3 groups. A significant association was found between the presence of diarrhea and detection of C perfringens enterotoxin (CPE) or toxin A via ELISA for both C perfringens and C difficile, respectively. PCR performed on C difficile isolates for toxin A and toxin B genes revealed no significant differences among the 3 groups, but diarrheic dogs were significantly more likely to be positive for the enterotoxin gene of C perfringens. Based on the results of this study, the use of ELISA for detection of CPE in feces combined with the detection of enterotoxigenic fecal isolates obtained via heat shock provides the strongest evidence for the presence of C perfringens-associated diarrhea.     

Bacteriological and molecular studies of Clostridium perfringens infections in newly born calves

Tropical Animal Health and Production - Clostridium perfringens is considered one of the important causes of calf diarrhea. Two hundred and twenty-seven clinical samples from newly born and dead...     

Antimicrobial susceptibilities of canine Clostridium difficile and Clostridium perfringens isolates to commonly utilized antimicrobial drugs

Clostridium difficile and Clostridium perfringens are anaerobic, Gram-positive bacilli that are common causes of enteritis and enterotoxemias in both domestic animals and humans. Both organisms have been associated with acute and chronic large and small bowel diarrhea, and acute hemorrhagic diarrheal syndrome in the dog. The objective of this study was to determine the in vitro antimicrobial susceptibilities of canine C. difficile and C. perfringens isolates in an effort to optimize antimicrobial therapy for dogs with clostridial-associated diarrhea. The minimum inhibitory concentrations (MIC) of antibiotics recommended for treating C. difficile (metronidazole, vancomycin) and C. perfringens-associated diarrhea in the dog (ampicillin, erythromycin, metronidazole, tetracycline, tylosin) were determined for 70 canine fecal C. difficile isolates and 131 C. perfringens isolates. All C. difficile isolates tested had an MIC of or=256 microg/ml for both erythromycin and tylosin. A third C. perfringens isolate had an MIC of 32 microg/ml for metronidazole. Based on the results of this study, ampicillin, erythromycin, metronidazole, and tylosin appear to be effective antibiotics for the treatment of C. perfringens-associated diarrhea, although resistant strains do exist. However, because there is limited information regarding breakpoints for veterinary anaerobes, and because intestinal concentrations are not known, in vitro results should be interpreted with caution.     

Recurrent diarrhea associated with enterotoxigenic Clostridium perfringens in 2 dogs

Two dogs were diagnosed with enterotoxigenic Clostridium perfringens-associated diarrhea. Diarrhea was responsive to antimicrobial therapy, but recurred after treatment was ceased. Clostridium perfringens enterotoxin was present in feces during diarrheic episodes but not when feces were normal. Both dogs responded to a prolonged course of oral cephalexin and dietary modification.     

Nosocomial diarrhea associated with enterotoxigenic Clostridium perfringens infection in dogs

A retrospective analysis of the medical records of 30 consecutive cases of diarrhea occurring in dogs that were hospitalized in a teaching hospital was performed. A prospective analysis of culture results for Clostridium perfringens of dogs with diarrhea were compared with those of a control nondiarrheal group. Hospital-acquired diarrhea in dogs was found to be associated with multiple serotypes of enterotoxigenic Clostridium perfringens. Other potential etiologic agents could not be isolated. Clinical signs were variable, and included mild depression, anorexia, and soft to watery diarrhea with or without frank blood, mucus, and tenesmus. Fever was not present. There were no hematologic or serum biochemical abnormalities, nor were there any consistent virologic or parasitologic findings. Salmonella spp or Campylobacter spp were not identified by fecal culture. No risk factors could be identified. A dog that was euthanatized on the day it developed diarrhea had intestinal histologic findings suggestive of clostridial enteritis. Dogs with diarrhea had significantly higher fecal clostridial counts than did dogs without diarrhea (mean log10 counts +/- SD = 6.34 +/- 1.79 vs 4.75 +/- 2.07). Enterotoxin was found in the feces of 41% of diarrheic dogs but in only 7% of dogs without diarrhea.