细菌药物钝化酶基因分布及其表达诱导与抑制机制的研究

目的：了解临床常见病原菌药物钝化酶基因及其优势基因携带模式，抗生素诱导药物钝化酶基因表达上调的作 用及其与细菌组氨酸激酶的关系。 方法：采用PCR和测序法，了解金黄色葡萄球菌、大肠埃希菌、肺炎克雷伯菌、鲍曼不动杆菌、阴沟肠杆菌临床菌株携带的β-内酰胺类、氨基糖苷类、大环内酯类钝化酶基因。采用实时荧光定量RT-PCR，了解抗生素诱导及组氨酸激酶阻断剂氯氰碘柳胺抑制药物钝化酶基因表达的作用。 结果：63株大肠埃希菌中检出4种β-内酰胺类、2种氨基糖苷类和1种大环内酯类钝化酶基因，优势基因携带模式为TEM＋CTX-M]＋aac(3)-Ⅱ＋mphA 16株（25.4%）和TEM＋CTX-M]＋aac(6′)-Ⅰb 13株（20.6%）。24株金黄色葡 萄球菌中检出2种β-内酰胺类、3种氨基糖苷类钝化酶基因，优势基因携带模式为aph(3′)（41.7%）或aac(6)-Ⅰe- aph(2)-Ⅰa（25.0%）。28株肺炎克雷伯菌中检出4种β-内酰胺酶、2种氨基糖苷类钝化酶基因，优势基因携带模式为 TEM＋SHV]＋aac(6′)-Ⅰb＋aac(3)-Ⅱ]（28.6%）和TEM＋SHV]＋aac(6′)-Ⅰb＋aac(3)-Ⅱ]＋mph（17.8%）。鲍曼不动杆菌和阴沟肠杆菌也以携带两类或三类药物钝化酶基因为优势模式。1/4 MIC青霉素、头胞噻肟和链霉素，能诱导3种β-内酰胺类和4种氨基糖苷类钝化酶基因表达显著上调（P<0.05），该诱导作用可被氯氰碘柳胺 所抑制（P<0.05）。 结论：上述临床常见病原菌多携带多类药物钝化酶基因并存在不同的优势基因携带模式。低浓度抗生素可能诱导药物钝化酶基因表达上调，但可被组氨酸激酶阻断剂所抑制。

Distribution of drug inactive enzyme genes in bacterial isolates and mechanism of its induction and inhibition

Objective： To determine the distribution and the predominant gene carrying model of drug inactive enzyme genes in bacterial isolates，and the mechanism of its induction and inhibition. Methods： The β-lactam，aminoglycosides and macrolides inactive enzyme genes were detected by PCR and sequencing in S.aureus, E.coli，K.pncumoniae, A.baumanii and E.cloacae isolates.The expression of inactive enzyme genes were examined by real-time fluorescent quantitative RT-PCR when the bacterial isolates were treated with antibiotics or a histidine kinase blocker closantel. Results： In 63 isolates of E.coli，4 kinds of β-lactam，2 aminoglycosides and 1 macrolides inactive enzyme-encoding genes were detected and the predominant gene-carrying models were TEM+CTX-M]+aac(3)-Ⅱ+mphA(25.4%) and TEM+CTX-M]+ aac(6′)-Ⅰb(20.6%).In 24 isolates of S.aureus，2 kinds of β-lactam and 3 aminoglycosides inactive enzyme-encoding genes were detected and the predominant gene-carrying models were aph(3′)(41.7%) or aac(6)-Ⅰe-aph(2)-Ⅰa(25.0%).In 28 isolates of K.pncumoniae，4 kinds of β-lactam and 2 aminoglycosides inactive enzyme-encoding genes were detected and the predominant gene-carrying models were TEM+SHV]+aac(6′)-Ⅰb+aac(3)-Ⅱ](28.6%) and TEM＋SHV]+aac(6′)-Ⅰb+aac(3)-Ⅱ]+ mphA(17.8%).The isolates of A.baumanii and E.cloacae also had a predominant model to carry 2 or 3 kinds of inactive enzyme-encoding genes.1/4 MIC of penicillin，cefotaxime or streptomycin induced the up-regulation of expression of 3 β-lactam or 4 aminoglycosides inactive enzyme-encoding genes(P<0.05)，and this effect was inhibited by closantel(P<0.05). Conclusions： The bacterial isolates frequently carry multiple kinds of inactive enzyme-encoding genes with different predominant gene-carrying models.Low concentration antibiotics can induce the up-regulation of inactive enzyme gene expression，which can be inhibited by histidine kinase blocker.