OBJECTIVE To compare the stability to β-lactamase-producing strains between cephalosporins like cefdi-toren and cefcapene and penicillin such as amoxicillin.METHODS The β-lactamase-producing clinical strains were screened out by nitrocefin chromogenic test,the supernatants containing β-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 calcu-lated with a hydrolysis rate of 100％of cephalothin so as to evaluate the stability of cefditoren to β-lactamase.RESULTS Cefditoren showed high antibacterial activity against the common clinical isolates of pathogens.The av-erage 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 the β-lactamase standards to cefditoren and cefcapene indicated that the β-lactamase had weaker affinity to cefditoren than cefcapene,while it had stronger stability to cefditoren than cefcap-ene.The drug resistance induction experiment showed that as compared with cefuroxime acid,cefdinir and amoxi-cillin,the Minimal inhibitory concentration(MIC)of cefditoren to E.coli and S.aureus rose slowly.CONCLUSION The relative hydrolysis rate of cefditoren to the β-lactamases secreted by E.coli and K.pneumoniae is the lowest among the tested antibiotics,the relative hydrolysis rate to the β-lactamases secreted by S.aureus ranks the front place,indicating that cefditoren has the strongest stability to the β-lactamases-producing strains.
CefditorenBacterial drug resistanceβ-lactamaseDrug resistance inductionStability
万方数据
维普
