头孢托仑对β-内酰胺酶的稳定性

Stability of cefditoren to β-lactamases

目的比较头孢托仑与头孢卡品等头孢类抗菌药物及阿莫西林等青霉素类抗菌药物对产β-内酰胺酶菌株稳定性的差异。方法采用头孢硝噻吩颜色反应筛选产β-内酰胺酶临床菌株,超声破碎后离心获得含β-内酰胺酶上清液,进而测定酶与不同抗菌药物底物共孵育后底物特征紫外吸收值的变化,以一代头孢头孢噻吩水解率为100%,计算抗菌药物的相对水解率来评价头孢托仑等抗菌药物对β-内酰胺酶的稳定性。结果头孢托仑对临床分离的常见致病菌的抗菌活性均较高;大肠埃希菌和肺炎克雷伯菌对头孢托仑的平均相对水解率均低于12%,其他两种三代头孢的相对水解率均超过了30%,而对二代头孢如头孢克洛,β-内酰胺酶的相对水解率均在85%以上;β-内酰胺酶标准品对头孢托仑和头孢卡品的反应动力学曲线结果表明β-内酰胺酶与头孢托仑的亲和力相较于头孢卡品弱,稳定性更强;耐药诱导实验显示,相较于头孢呋辛酸、头孢地尼和阿莫西林,头孢托仑对大肠埃希菌及金黄色葡萄球菌的最小抑菌浓度(MIC)表现出缓慢上升。结论头孢托仑对大肠埃希菌和肺炎克雷伯菌分泌的β-内酰胺酶相对水解率均为所测抗菌药物中最低,且对于金黄色葡萄球菌分泌的β-内酰胺酶相对水解率位于所测抗菌药物前列,表明头孢托仑对产β-内酰胺酶菌株稳定性最强。

OBJECTIVE To compare the stability toβ-lactamase-producing strains between cephalosporins like cefditoren and cefcapene and penicillin such as amoxicillin.METHODS Theβ-lactamase-producing clinical strains were screened out by nitrocefin chromogenic test,the supernatants containingβ-lactamase were centrifugally extracted by ultrasonic crushing.The enzyme was co-incubated with different antibiotic substrates to determine the change of ultraviolet absorption value of substrate characteristics,and the relative hydrolysis rate of antibiotics was calculated with a hydrolysis rate of 100%of cephalothin so as to evaluate the stability of cefditoren toβ-lactamase.RESULTS Cefditoren showed high antibacterial activity against the common clinical isolates of pathogens.The average relative hydrolysis rate of Escherichia coli and Klebsiella pneumoniae to cefditoren was less than 12%,the relative hydrolysis rate to the other two types of third generation cephalosporins was more than 30%,while the relative hydrolysis rate to the second generation cephalosporins like cefaclor,β-lactamases was more than 85%.The result of reaction kinetics curve for theβ-lactamase standards to cefditoren and cefcapene indicated that theβ-lactamase had weaker affinity to cefditoren than cefcapene,while it had stronger stability to cefditoren than cefcapene.The drug resistance induction experiment showed that as compared with cefuroxime acid,cefdinir and amoxicillin,the Minimal inhibitory concentration(MIC)of cefditoren to E.coli and S.aureus rose slowly.CONCLUSION The relative hydrolysis rate of cefditoren to theβ-lactamases secreted by E.coli and K.pneumoniae is the lowest among the tested antibiotics,the relative hydrolysis rate to theβ-lactamases secreted by S.aureus ranks the front place,indicating that cefditoren has the strongest stability to theβ-lactamases-producing strains.