整合子在表皮葡萄球菌中的分布及苦参碱对Ⅰ类整合酶基因表达量影响的研究

发布时间：2018-10-17 19:23

【摘要】：金黄色葡萄球菌、链球菌和大肠杆菌是引起奶牛乳房炎的主要致病菌,而表皮葡萄球菌(Staphylococcus epidermidis,Se)被认为致病能力弱的条件致病菌,一般不引起奶牛乳房炎疾病的爆发。随着研究的深入,发现表皮葡萄球菌极易在奶牛乳房环境中形成生物被膜,形成的生物被膜是金黄色葡萄球菌耐药株的储备库,这些生物特点导致细菌耐药性上升并呈现多重药耐药性特征。研究表明,细菌整合子系统在细菌耐药性形成过程中扮演着重要的角色,它在整合酶的介导下可以直接捕获外界耐药基因,使耐药基因转移扩散致使多种类型的耐药基因盒产生,耐药基因盒的表达导致细菌多重耐药性的形成。鉴于整合子在细菌耐药性形成过程中的重要作用,研究菌株整合子与耐药性关系以及药物对其作用特点,具有重要的理论和应用价值。本研究首先通过药理学和分子生物学手段对分离的临床型奶牛乳房炎Se进行耐药性和整合子分布特点分析,深入探讨整合子与Se耐药相关性。分析发现,临床分离的Se对临床常用抗菌药物的耐药率为16.7%-100%,耐药谱广,呈多重耐药的特点,所有分离株对青霉素的耐药率最高；通过对细菌整合子流行特征研究,Ⅰ类整合子的检出率为60%,Ⅱ类整合子的检出率为16.7%,菌株中未检查出Ⅲ类整合子。其中产膜Se中Ⅰ类整合子检出率为71.4%,不产膜Se中Ⅰ类整合子的检出率为56.5%。且在Se中,Ⅰ类整合子阳性菌株的耐药率大于阴性菌株。从结果中可以看出Se中Ⅰ类整合子的检出率最高,并且和Se的耐药性有一定相关性；在含有Ⅰ类整合子的Se中耐药基因盒的检出率为77.8%,并发现每个耐药基因盒至少携带两个耐药基因,其中氨基糖苷乙酰转移酶、二氢叶酸还原酶、氯霉素乙酰基转移酶是最常见的耐药基因。在Se中,Ⅰ类整合子携带的基因盒阳性菌株耐药种数高于基因盒阴性菌株,说明整合子携带的耐药基因盒与细菌产生多重耐药性有密切关联。同时研究了生物被膜菌和浮游菌中Ⅰ类整合酶基因的表达量,以及药物对Ⅰ类整合酶基因表达量的影响。结果表明,生物被膜菌和浮游菌中均有Ⅰ类整合酶基因的表达,且生物被膜菌Ⅰ类整合酶基因的表达量均高于浮游菌,随着生物被膜的不断加厚Ⅰ类整合酶基因的表达量也不断升高。生物被膜密度的增大,可能会影响整合子捕获耐药基因的频率,有利于耐药基因的扩散。苦参碱对产膜Se的MIC高于或等于不产膜Se的MIC,并且苦参碱对Se生物被膜有抑制作用。苦参碱对Se的生物被膜菌和浮游菌两种生长状态下的Ⅰ类整合酶基因有调控作用,可以下调Ⅰ类整合酶基因的表达量,其中对浮游菌生长状态下Ⅰ类整合酶基因下调最大。提示苦参碱能够降低Ⅰ类整合子传递耐药基因的效率,能够起到阻止耐药基因的传播和细菌耐药性的形成,具体机制仍需进一步深层次研究。
[Abstract]:Staphylococcus aureus, Streptococcus aureus and Escherichia coli are the main pathogens causing mastitis in dairy cows. Staphylococcus epidermidis (Staphylococcus epidermidis,Se) is considered to be a conditional pathogen with weak pathogenicity. With the development of research, it was found that Staphylococcus epidermidis is easy to form biofilm in cow breast environment, and the biofilm formed is the reserve of staphylococcus aureus resistant strains. These biological characteristics lead to an increase in bacterial resistance and multidrug resistance. Studies have shown that the bacterial integration subsystem plays an important role in the formation of bacterial resistance, and it can directly capture the genes of external drug resistance mediated by integrase. The expression of drug resistance gene box resulted in the formation of multidrug resistance of bacteria. In view of the important role of integron in the formation of bacterial drug resistance, it is of great theoretical and practical value to study the relationship between integron and drug resistance, as well as the action characteristics of drugs. In this study, drug resistance and integron distribution of Se in clinical mastitis were analyzed by pharmacology and molecular biology, and the relationship between integron and Se resistance was discussed. It was found that the resistance rate of clinically isolated Se to commonly used antimicrobial agents was 16.7- 100, with a wide spectrum of resistance and multidrug resistance, and the highest resistance rate of all isolates to penicillin was observed, and the epidemiological characteristics of bacterial integron were studied. The detectable rate of class 鈪，

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