中华流行病学杂志  2022, Vol. 43 Issue (11): 1860-1868   PDF    
http://dx.doi.org/10.3760/cma.j.cn112338-20220316-00189
中华医学会主办。
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文章信息

郑浩然, 白璐璐, 王媛媛, 钟佳鑫, 卢金星, 邓慧玲, 谢群, 吴媛.
Zheng Haoran, Bai Lulu, Wang Yuanyuan, Zhong Jiaxin, Lu Jinxing, Deng Huiling, Xie Qun, Wu Yuan
产气荚膜梭菌毒素研究进展
Progress in research of Clostridium perfringens toxin
中华流行病学杂志, 2022, 43(11): 1860-1868
Chinese Journal of Epidemiology, 2022, 43(11): 1860-1868
http://dx.doi.org/10.3760/cma.j.cn112338-20220316-00189

文章历史

收稿日期: 2022-03-16
产气荚膜梭菌毒素研究进展
郑浩然1,2 , 白璐璐2 , 王媛媛2 , 钟佳鑫2 , 卢金星2 , 邓慧玲3 , 谢群4 , 吴媛2     
1. 陕西中医药大学, 西安 712046;
2. 中国疾病预防控制中心传染病预防控制所, 北京 102206;
3. 西安市中心医院, 西安 710003;
4. 湘南学院公共卫生学院, 郴州 423000
摘要: 产气荚膜梭菌通过产生大量的毒素导致人类和动物患气性坏疽、肠炎和肠毒素血症。目前,已知产气荚膜梭菌可产生20多种毒素和水解酶。不同的毒素类型与特定的疾病类型相关。毒素分型已由毒素基因的分子检测替代了传统的血清分型方法。因此本文围绕产气荚膜梭菌毒素种类、基本特征、致病机制以及与疾病的关系进行系统回顾总结和展望,为后续的毒素分型等快速检测技术的建立、免疫抗原筛选、抗体制备以及相关致病机制研究提供基础。
关键词: 腹泻    毒素    产气荚膜梭菌    
Progress in research of Clostridium perfringens toxin
Zheng Haoran1,2 , Bai Lulu2 , Wang Yuanyuan2 , Zhong Jiaxin2 , Lu Jinxing2 , Deng Huiling3 , Xie Qun4 , Wu Yuan2     
1. Shaanxi University of Traditional Chinese Medicine, Xi'an 712046, China;
2. National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China;
3. Xi'an Central Hospital, Xi'an 710003, China;
4. School of Public Health, Xiangnan University, Chenzhou 423000, China
Abstract: Clostridium perfringens can produce many kinds of toxins and hydrolase, causing gas gangrene, enteritis and enterotoxemia in both human and animals. It is known that C. perfringens can produce more than 20 toxins and hydrolases. The different toxin types are associated with specific disease types. At present, molecular toxin-typing method by PCR has replaced the traditional serological typing method. In this study, we systematically summarize the types, basic characteristics, pathogenic mechanism and the relationship with disease of C. perfringens toxins to provide evidence for the establishment of rapid detection method, immune antigen screening, antibody preparation and research of related pathogenic mechanism.
Key words: Diarrhea    Toxin    Clostridium perfringens    

产气荚膜梭菌(Clostridium perfringens)是一种革兰染色阳性且严格厌氧的细菌,能够产生对外界环境具有抗性的芽孢,因此,产气荚膜梭菌能够广泛存在于土壤、污水、食物及动物(包括人类)的正常肠道微生物群中[1]

产气荚膜梭菌最初根据其产酸产气能力分为产酸型和产气型2种不同的亚型[2]。1933年,Wilsdon通过毒素中和试验,根据菌株产生的α毒素(Clostridium perfringens α-toxin)、β毒素(Clostridium perfringens β-toxin)、ε毒素(Clostridium perfringens ε-toxin)将产气荚膜梭菌分为4种不同的类型(A~D型),这种分型方法自提出后经过4次修改(1933年、1943年、1962-1964年、2018年),被视为产气荚膜梭菌的经典分型方法[1-2]。根据产气荚膜梭菌产生的6种主要毒素(表 1):α毒素、β毒素、ε毒素和ι毒素(Clostridium perfringens ι-toxin)、肠毒素(Clostridium perfringens enterotoxin,CPE)和坏死性肠炎B毒素(Necrotic enteritis B-like toxin,NetB)的组合不同,将其分为A~G型7种类型(2018年以前的分型方案仅有A~E型5种,其中A、C、F型与人类疾病密切相关)。除此之外,不同毒素类型的菌株可能还携带1种或多种不参与分型毒素如β2毒素(Clostridium perfringens β2-toxin)、产气荚膜梭菌溶素O/θ毒素(Perfringens O/Clostridium perfringens θ toxin)、坏死性肠炎F毒素(Necrotic enteritis F-like toxin,NetF)、产气荚膜梭菌二元肠毒素(Binary enterotoxin of Clostridium perfringens,BEC)、产气荚膜梭菌λ毒素(Clostridium perfringens λ-toxin)等,目前尚未发现一种菌株能够携带全部的毒素[2]

表 1 产气荚膜梭菌毒素分型及引发的相关疾病

随着现代分子生物学方法与技术的快速发展,基于基因特征分型的方法更有利于对那些引发感染性疾病的菌株进行流行病学调查,与动物毒素中和试验、毒素抗体检测试剂盒相比,分子检测方法能够快速、灵敏、经济地对毒素基因进行检测,以便了解样本菌株的型别,对于临床诊断和治疗具有重要意义。不仅如此,新技术的应用使产气荚膜梭菌毒素的相关研究也日益深入,现就产气荚膜梭菌部分毒素的研究进展进行综述。

一、产气荚膜梭菌毒素

目前已经发现产气荚膜梭菌能够产生20多种细胞毒素和水解酶(表 2),二者在致病的过程中具有相互协同的作用(图 1)。

表 2 产气荚膜梭菌相关毒素特征
注:Iota a & Iota b:产气荚膜梭菌ι毒素;CPE:产气荚膜梭菌肠毒素;NetB:坏死性肠炎B毒素;NetF:坏死性肠炎F毒素;BEC:产气荚膜梭菌二元肠毒素;MLKL:混合连接激酶结构域样蛋白 图 1 产气荚膜梭菌部分毒素、酶和蛋白的作用方式

1. 用于产气荚膜梭菌分型的主要毒素:

(1)α毒素:产气荚膜梭菌菌株均携带,是目前被研究最多的一种大小为42.5 kDa的酶,具有磷脂酶C和鞘磷脂酶的生物学活性[23-24],编码基因cpa/plc位于染色体上,大小为1 200 bp(表 2)。α毒素拥有2个结构域,N端锌结合结构域具有催化毒素的作用,C端钙结合结构域负责毒素与细胞膜的结合[25]图 2A)。α毒素可直接发挥酶活性破坏宿主细胞膜的功能,导致细胞溶解和组织坏死(图 1)。除此之外,α毒素还可以同神经节苷脂GM1受体结合激活多种信号通路,诱导受影响的细胞氧化应激和白细胞介素-8的产生[26-27]。有研究表明,α毒素的C端结构域(247~370 aa)可以保护小鼠模型免遭气性坏疽和CPE的侵袭[28-29]。因此认为α毒素的没有毒性的C端结构域对于疫苗的开发是有前景的抗原成分[30]

图 2 产气荚膜梭菌结构功能示意图

(2)β毒素:由B和C型产气荚膜梭菌产生,是一种大小为35 kDa的蛋白,编码基因cpb位于质粒上,大小为1 011 bp(表 2)。在氨基酸水平上与金黄色葡萄球菌产生的成孔毒素(α毒素)具有28%的相似性,β毒素能在宿主膜表面形成功能性质膜孔(图 1),这种七聚体形式的质膜孔能够导致大量的钙离子、钠离子、氯离子进入细胞,导致细胞肿胀凋亡[4, 31]

目前认为在不同的细胞类型或不同物种的宿主中,β毒素的受体可能有所不同。Nagahama等[32]研究认为嘌呤受体(P2X7)是β毒素与宿主细胞结合的位点,例如人胚胎肾细胞(HEK-293)本不能与β毒素结合,当转染产生P2X7后,细胞能够结合β毒素并形成寡聚体。然而,根据Bruggisser等[33]最新的研究结果认为血小板内皮细胞黏附分子-1(PECAM-1或CD31)是肠黏膜内皮细胞上的一种β毒素与宿主细胞结合的受体,研究报告显示肠黏膜表面的“细胞屏障”(上皮层)主要是由肠上皮细胞构成的,而这种包含P2X7受体的肠上皮细胞所构成的“细胞屏障”不能与产气荚膜梭菌产生的β毒素相结合。实验显示β毒素可与固有层的血管内皮细胞结合从而导致急性出血性坏死性肠炎的发生,因此P2X7不能用来单独解释β毒素引起坏死性肠炎的致病机制。此外,该研究还发现CD31并不在上皮细胞中表达[33-34]

(3)ε毒素:由B和D型产气荚膜梭菌菌株产生,编码基因etx位于质粒上,大小为1 119 bp(表 2),需要在肠道蛋白酶水解激活的情况下才能发挥其全部的功能[35]。ε毒素通常以33 kDa的原毒素形式进入到宿主的肠腔中,被细胞外胰蛋白酶、糜蛋白酶以及产气荚膜梭菌中的λ毒素去除部分N末端和C末端的残基将其活化,活化后的ε毒素大小为29 kDa,毒性强度是原毒素的1 000倍[36-37]。通过功能获得和损失实验的组合认为髓鞘和淋巴细胞蛋白可能是ε毒素的候选受体[38]。ε毒素拥有3个结构域(图 2B):结构域1为N端结构域,负责毒素与宿主细胞的受体结合;结构域2为位于N端和C端中间的结构域,包含着一个β发夹结构,在形成孔隙的过程中介导毒素的插入;结构域3为C端结构域,在毒素寡聚化的过程中起作用[39]

(4)ι毒素:仅由E型产气荚膜梭菌菌株产生,属于梭状芽孢杆菌二元毒素家族(艰难梭菌CDT毒素、肉毒梭菌C2毒素等)中的一员,由2个独立的成分组成,酶成分和结合成分,分别称为Iota a(Ia)和Iota b(Ib)[40]。Ia和Ib的编码基因位于质粒上,分别被称为iapibp,编码基因大小分别为1 365 bp和2 622 bp(表 2)。ι毒素本身没有活性,当蛋白酶或菌株自身携带的λ毒素从Ia和Ib原蛋白的N末端去除部分氨基酸序列时会使它们产生活性[41]。被激活后的Ia包括一个负责与Ib相互作用的N端结构域和一个具有二磷酸腺苷核糖基转移酶活性的C端结构域(图 2C)。活化后的Ib有4个结构域,分别介导与Ia的相互作用、使毒素进入宿主细胞、介导寡聚、与受体(脂解刺激蛋白)结合[42]图 2D)。

ι毒素作用的产生起始于Ib与宿主细胞上的受体结合形成插入到靶细胞质膜中的七聚体孔道[43]。然后,全毒素经内吞作用进入宿主细胞,Ia利用Ib寡聚后形成的孔道迁移到细胞质中,发挥酶活性诱导宿主细胞骨架解体,最终导致细胞凋亡[44-45]图 1)。

(5)CPE:是一种大小为35 kDa的单链多肽,编码基因cpe既可以位于染色体上也可以位于质粒上,大小为957 bp(表 2)。该毒素由所有的F型产气荚膜梭菌产生,也能由部分C、D和E型负责产气荚膜梭菌产生[46]。CPE的晶体结构显示该毒素由一个与宿主细胞受体结合的C末端结构域和一个具有细胞毒性的N末端结构域构成[47-48]图 2E)。

CPE的作用起始于它与宿主细胞的claudin蛋白结合。该受体由4个跨膜区和2个细胞外环路(ECL1和ECL2)构成,对于维持上皮细胞和内皮细胞间紧密连接的结构和功能非常重要[49]。CPE的C末端结构域与受体结合,形成一个大小为90 kDa的复合物,该复合物除CPE本身外还包括claudin-3和/或claudin-4,以及claudin-1蛋白[50]。在37 ℃时,6个小的CPE复合物迅速在宿主细胞膜表面寡聚化形成一个大的前孔复合物,将其命名为CH-1复合物(约540 kDa)。然后,位于前孔复合物中的每个CPE延伸出一个β发夹环,6个β发夹环聚集形成一个β桶状蛋白结构插入宿主细胞膜中,形成一个大小为1.4 nm的通道[51]。由CH-1复合物形成的通道可以渗透钙离子流入细胞质中从而导致宿主细胞死亡,由于CPE的浓度不同,导致流入细胞质中的钙离子浓度不同。因此,不同浓度的CPE对于钙蛋白酶的激活程度不同[52-53]。当CPE浓度较低(1 µg/ml)时,只能引起少量的钙离子内流,钙蛋白酶被轻度激活,触发半胱天冬酶-3介导的细胞凋亡;CPE浓度较高(10 µg/ml)则会引起大量的钙离子内流,钙蛋白酶被强烈地激活,导致混合谱系激酶结构域样蛋白依赖性坏死(图 1)。此外,接近失活的CPE也会导致宿主细胞发生形态学损伤,导致基底外侧细胞膜表面暴露,CPE与另一种紧密连接组分闭合蛋白(occludin)相互作用,形成一个大小约为600 kDa的CPE复合物,称为CH-2复合物。目前尚不清楚CH-2复合物对CPE致病作用的贡献[50]

(6)NetB:仅由G型产气荚膜梭菌产生,具有物种特异性,可导致禽类动物发生小肠坏死[54]。NetB是一种大小为33 kDa的单链蛋白,编码基因netB位于质粒上,大小为1 371~1 533 bp(表 2)。与该家族的其他毒素相同,NetB与宿主细胞的受体结合后,在细胞表面寡聚,导致细胞病变孔隙(1.6~1.8 nm)的形成[55]。关于NetB与受体结合的位置仍存在着较大争议。之前的研究认为,NetB毒素在寡聚化的过程中需要宿主细胞脂筏当中的胆固醇参与[56]。最近的研究表明,NetB与宿主结合的位置不在脂筏区域,并且在寡聚化的过程中也不需要胆固醇的参与[57]

2. 不用于产气荚膜梭菌分型的次要毒素:

(1)θ毒素:除了携带染色体cpe基因的F型产气荚膜梭菌和导致急性出血性坏死性肠炎的C型产气荚膜梭菌外,大多数产气荚膜梭菌菌株都可以产生θ毒素[42]。θ毒素是一种大小为54 kDa的蛋白,编码基因位于染色体上,大小为1 500 bp(表 2)。θ毒素拥有4个结构域(图 2G):结构域4负责与宿主细胞的接触,接触后使结构域3中的2个α螺旋结构域改变构象形成2个β发夹插入宿主细胞膜中[1, 42, 58]。这种改变能够使毒素穿透细胞膜并形成15 nm的“大孔”(图 1),这比产气荚膜梭菌中其他成孔毒素形成的致病孔(1.6~1.8 nm)要大得多,但“大孔”破坏宿主细胞渗透压失衡最终导致细胞溶解的作用并不是引发气性坏疽的关键因素[59]

(2)β2毒素:携带β2毒素的产气荚膜梭菌菌株可以从各种野生和家养动物、人类中分离,也可以从食物、土壤中分离[60]。β2毒素是一种大小为28 kDa的成孔毒素,编码基因cpb2位于质粒上,大小为795 bp(表 2)。虽然名字与β毒素相似,但是二者之间的氨基酸序列没有明显的同一性(< 15%)[61]。尽管该毒素的首次发现是从患有由产气荚膜梭菌导致的坏死性肠炎的仔猪中鉴定得到的,但由于该毒素能够广泛存在于所有类型的菌株当中,β2毒素在菌株致病过程中扮演的角色仍需要进一步的研究[62-63]

(3)NetF:2015年的研究发现NetF与犬急性出血性胃肠炎和马驹坏死性小肠结肠炎病例中分离出的A型菌株之间存在非常显著的关联[15]。NetF是一种大小为31.7 kDa的单链蛋白,编码基因netF位于质粒上,大小为918 bp,氨基酸序列与NetB有48%的同一性(表 2)。具有成孔能力,孔隙的大小可能为6~8 nm[64]。在最新的分型法则中将该毒素列为潜在的分型毒素,但缺少相关实验(如分子科赫假设)的证实[2]

(4)BEC:该毒素似乎与日本几次大规模暴发的急性食源性胃肠炎相关,而导致相关疾病的产气荚膜梭菌菌株中并未分离出CPE及其他可能的病原体,随着研究的深入,BEC被发现是导致本次食源性肠胃炎暴发的原因[65]。和ι毒素一样,该毒素也由2个独立的成分组成,即酶效应成分(BEC a)和细胞结合成分(BEC b)分别与ι毒素的单个成分有43%~44%的氨基酸序列同一性(表 2)。目前,经过纯化的BEC a已经被证明具有肌动蛋白二磷酸腺苷核糖基转移酶活性,但目前尚不清楚BEC b结构功能及其与受体结合的位置[66]。一般来说,二元毒素只有当2种成分一起作用时才会对靶细胞产生影响,这些成分作为个体存在时并不发挥生物活性。但是BEC与其他二元毒素不同,在乳鼠试验中即便没有酶成分BEC a的参与,BEC b也具有生物活性,能够导致宿主肠道内液体积聚(图 1[66-67]。由于目前尚不清楚BEC b对靶细胞的作用模式,因此与NetF相同,BEC也被列为潜在的分型毒素。

二、产气荚膜梭菌引发的主要疾病

1. A型产气荚膜梭菌:在气性坏疽发生的过程中,A型产气荚膜梭菌的α毒素能与宿主体内多种细胞和组织产生效应从而发挥重要作用,包括溶血、肌坏死、白细胞生长停滞、血小板聚集、血管收缩和抑制中性粒细胞的分化[68]。此外,菌株中的θ毒素还能与α毒素协同作用,导致宿主组织的外周血管和细胞外基质中的白细胞生长停滞,最终导致肌坏死[1]。A型产气荚膜梭菌除了对于导致人类和动物感染气性坏疽十分重要之外,还被认为是导致牛坏死性出血性肠炎(也称牛肠毒血症)的疑似病原体,虽然已经在牛肠袢模型中得到了证实,但是由于产气荚膜梭菌引发的各种动物的肠道疾病通常是由B~G型所引起的,因此A型产气荚膜梭菌在肠道疾病中的真正作用仍然存在争议[69-70]

2. B型产气荚膜梭菌:是导致羔羊痢疾的主要原因,但也有少量报道称这种疾病在牛和马中也可出现[71]。这种疾病的主要特征是宿主发生坏死性出血性肠炎,极少数的病例中也出现神经系统症状,如局灶性对称性坏死,以上2种症状分别被认为是由B型产气荚膜梭菌产生的β毒素和ε毒素引起。Rumah等[72]从一名多发性硬化症(MS)患者的粪便中分离出B型产气荚膜梭菌并在该疾病患者中发现ε毒素的血清抗体,但是目前还没有确凿的证据证实B型产气荚膜梭菌与MS之间的真正关系[72-73]

3. C型产气荚膜梭菌:引发的疾病通常是急性的且具有高度的致死性。C型产气荚膜梭菌是引发人患急性坏死性出血性肠炎和其他哺乳动物发生坏死性肠炎的主要原因。这种疾病通常发生在患者长期食用富含大量胰蛋白酶抑制剂的食物后,又食用了一些被C型产气荚膜梭菌污染的食物(如未加工熟的猪肉)。此外,在糖尿病患者和其他胰腺功能减退的患者中也有感染C型产气荚膜梭菌的病例报告[74]。新出生的动物对该菌株具有较强的易感性,新出生动物因食用富含大量蛋白酶抑制剂的初乳导致患病风险增加[75]。这些证据说明胰蛋白酶是抵抗C型产气荚膜梭菌感染的重要因素。

4. D型产气荚膜梭菌:引发的疾病根据严重程度被分为超急性、急性、亚急性、慢性4种不同的类型[76]。超急性症状表现为,当大量的毒素进入血液循环当中,会导致绵羊发生没有任何征兆的猝死。D型产气荚膜梭菌引发的急性中毒会导致绵羊抽搐、昏迷最终死亡。慢性症状通常发生于ε毒素浓度较低或接种过疫苗后感染D型产气荚膜梭菌的绵羊中,被感染的宿主通常会表现出临床病程较长的神经系统症状,包括失明、共济失调等。在部分亚急性、慢性中毒的山羊当中会出现坏死性出血性结肠炎或小肠结肠炎,伴或不伴有肠毒素血症,而在绵羊当中并没有发现类似的肠道损伤[77]。虽然D型产气荚膜梭菌在动物中可引发严重的肠毒素血症,但目前尚无文献报道其可以引发人类的中毒。

5. E型产气荚膜梭菌:存在于许多健康的动物和人类的肠道中,因此E型产气荚膜梭菌的致病作用目前尚未阐述清楚。不过在2种动物(山羊和新出生的小牛)和人类中已经描述了少数E型产气荚膜梭菌引发相关疾病的病例[78-79]

6. F型产气荚膜梭菌:F型产气荚膜梭菌中编码CPE的基因位置不同,导致的疾病也不同,编码基因位于染色体上的F型产气荚膜梭菌(FC)通常导致食源性疾病(如食物中毒);编码基因位于质粒上的F型产气荚膜梭菌(FP)通常导致非食源性肠道疾病[如抗生素相关性腹泻(AAD)、散发性腹泻]。

(1)食源性疾病:食物中毒引发的症状通常包括腹泻和腹部痉挛,12~24 h内发展,24 h后恢复,症状较轻常呈自限性[80]。然而,由FC型产气荚膜梭菌引发的食物中毒可导致身体虚弱的人群、老年人以及在精神病院接受治疗的年轻患者死亡[81-82]。造成死亡的原因是胃肠道功能下降或因患有其他疾病服用药物导致的胃肠道相关副作用[1, 83]。当感染了FC型产气荚膜梭菌后,患者不会出现腹泻的症状,肠道内的CPE与肠道之间的长时间接触促进了毒素进入血液循环,损伤肝、肾等内脏器官从而导致了致命的肠毒素血症。

(2)非食源性胃肠道疾病:在所有非食源性胃肠道疾病中,FP型产气荚膜梭菌引起的病例约占5%~15%[84]。与该菌株引发的食源性疾病相比,FP型产气荚膜梭菌引发的胃肠道疾病通常持续时间更长(长达数周)且病情更为严重[85]。在医院环境中,接受抗生素治疗的患者(尤其是老年人)容易被医院环境中的FP型产气荚膜梭菌感染,随后这些菌株在宿主体内产生CPE从而引发AAD。

7. G型产气荚膜梭菌:可引发禽类物种的坏死性肠炎,是全球范围内家禽养殖业常见的疾病,给该产业每年造成了约2亿~60亿美元的损失,目前尚未发现G型菌株在非禽类物种中的病例描述[86]

三、总结与展望

本综述介绍了产气荚膜梭菌部分毒素以及不同型别菌株引发的疾病。产气荚膜梭菌引发的动物疾病目前已被国家规定为二类动物疫病[87]。近些年来,相关领域的科研工作者们正在加快疫苗的研发以减轻该菌所带来的产业经济损失。产气荚膜梭菌菌株产生的ε毒素的毒性强度仅次于肉毒杆菌毒素、破伤风梭菌毒素[88]。ε毒素已被美国CDC列为B类生物恐怖战剂[89]。产气荚膜梭菌还是一种能够引起人类或动物患上包括气性坏疽、坏死性肠炎、食物中毒和非食源性肠道疾病的重要病原微生物,且被美国、日本及欧盟部分国家列为细菌性食源性疾病暴发的主要原因[90-92]。与其他国家相比,我国由该菌引发的细菌性食源性疾病的病例报道却较为少见。在非食源性肠道疾病中,尽管艰难梭菌被认为是引发该病的关键因素,占所有病例的10%~33%,产气荚膜梭菌在AAD的发病过程中也扮演着关键的角色。来自伊朗对于医院内艰难梭菌进行常规监测的研究中发现由产气荚膜梭菌引发AAD的比例为22.4%(68/303)且50岁以上的患者出现由产气荚膜梭菌引发AAD的风险远远高于年轻患者[93]。文献Meta分析显示,从2001-2021年全球范围内的住院患者中,由艰难梭菌、产气荚膜梭菌引发的AAD占比分别为19.6%、14.9%[94]。在我国关于产气荚膜梭菌在医院中引发抗生素性腹泻的流行情况缺乏相关的系统研究。不过,在我国河南省的一家医院对于艰难梭菌进行常规检测的过程中发现由产气荚膜梭菌引发的AAD的比例为4.3%(48/1 108),该研究同时指出在该医院年龄超过50岁以及患有癌症、肝胆系统疾病的患者更容易感染FP型和A型产气荚膜梭菌[95]。除此之外,本实验室在对于艰难梭菌的常规监测过程中,发现产气荚膜梭菌引发AAD的比例甚至超过了艰难梭菌。随着我国人口老龄化的趋势不断加速,未来在医院中会有更多老年住院患者,产气荚膜梭菌引起AAD的风险也会显著增加,因此,医疗机构和CDC应加强或开展与产气荚膜梭菌相关疾病的检测,尤其是不同毒素型产气荚膜梭菌的精准快速鉴别。

许多参与产气荚膜梭菌分型的主要毒素的致病机制尚未明确,比如α毒素对于引发人类和动物胃肠道疾病是否发挥作用、ε毒素与受体结合的真正位置等。除了参与分型的主要毒素之外,产气荚膜梭菌产生的其他毒力因素如唾液酸酶(NanI、NanJ、NanH)的研究也在进行当中,但目前仍处于起步阶段,需要更多的研究来证实这些因素在菌株致病过程中的真正作用。

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