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艰难梭菌的内在D类β-内酰胺酶

发布者:抗性基因网 时间:2019-01-04 浏览量:942

摘要

艰难梭菌(Clostridium difficile)是致命的艰难梭菌感染的致病因子。病原体对β-内酰胺抗生素的抗性在疾病的发展中起主要作用,但抗性机制目前尚不清楚。我们发现艰难梭菌编码D类β-内酰胺酶,即CDD,它是该物种固有的。我们研究了两种CDD酶CDD-1和CDD-2,并显示它们对各种β-内酰胺抗生素(包括青霉素和扩展的头孢菌素)显示出广谱,高催化效率。我们证明cdd基因在其自身启动子的控制下表达很差,并且仅部分地对观察到的对β-内酰胺的抗性有贡献。然而,当cdd1基因在抗生素敏感的Clostridium cochlearium菌株中在有效启动子的控制下表达时,它产生对β-内酰胺的高水平抗性。总之,在该工作中确定的结果证明了内源性Dβ-内酰胺酶在艰难梭菌中的存在,其构成了能够赋予对β-内酰胺抗生素的广谱,临床相关水平的抗性的高效酶的储库。这一发现对阐明临床上重要的病原体艰难梭菌对β-内酰胺类抗生素的耐药机制有重要贡献。重要性C.艰难梭菌是一种形成孢子的厌氧菌,可引起大肠高感染死亡率。艰难梭菌感染难以预防和治疗,因为病原体对许多抗微生物剂具有抗性。长期使用β-内酰胺类抗生素治疗各种传染病会引发感染,因为这些药物会抑制大量保护性肠道细菌,使抗性艰难梭菌细菌繁殖。虽然艰难梭菌对β-内酰胺抗生素的抗性在疾病的发展中起主要作用,但抗性机制尚不清楚。我们研究的重要意义在于发现β-内酰胺酶的艰难梭菌,即破坏β-内酰胺类抗生素的酶。这些发现最终有助于对抗致命的艰难梭菌感染。


Clostridium difficile is the causative agent of the deadly C. difficile infection. Resistance of the pathogen to β-lactam antibiotics plays a major role in the development of the disease, but the mechanism of resistance is currently unknown. We discovered that C. difficile encodes class D β-lactamases, i.e., CDDs, which are intrinsic to this species. We studied two CDD enzymes, CDD-1 and CDD-2, and showed that they display broad-spectrum, high catalytic efficiency against various β-lactam antibiotics, including penicillins and expanded-spectrum cephalosporins. We demonstrated that the cdd genes are poorly expressed under the control of their own promoters and contribute only partially to the observed resistance to β-lactams. However, when the cdd1 gene was expressed under the control of efficient promoters in the antibiotic-sensitive Clostridium cochlearium strain, it produced high-level resistance to β-lactams. Taken together, the results determined in this work demonstrate the existence in C. difficile of intrinsic class D β-lactamases which constitute a reservoir of highly potent enzymes capable of conferring broad-spectrum, clinically relevant levels of resistance to β-lactam antibiotics. This discovery is a significant contribution to elucidation of the mechanism(s) of resistance of the clinically important pathogen C. difficile to β-lactam antibiotics.IMPORTANCE C. difficile is a spore-forming anaerobic bacterium which causes infection of the large intestine with high mortality rates. The C. difficile infection is difficult to prevent and treat, as the pathogen is resistant to many antimicrobial agents. Prolonged use of β-lactam antibiotics for treatment of various infectious diseases triggers the infection, as these drugs suppress the abundance of protective gut bacteria, allowing the resistant C. difficile bacteria to multiply. While resistance of C. difficile to β-lactam antibiotics plays the major role in the development of the disease, the mechanism of resistance is unknown. The significance of our research is in the discovery in C. difficile of β-lactamases, enzymes that destroy β-lactam antibiotics. These findings ultimately can help to combat deadly C. difficile infections.


https://www.ncbi.nlm.nih.gov/pubmed/30563905