【摘要】 应用药物梯度琼脂筛选法获得绿脓杆菌和阴沟杆菌的Ceftazidime耐药菌株(MIC≥64μg/ml)。采用紫外分光光度法检测了耐药菌的β-内酰胺酶活性,酶对12种β-内酰胺抗生素水解的“底物轮廓”以及抑酶活性;应用超薄层分析等电聚焦电泳技术检测了β-内酰胺酶的等电点(pI),并与标准产酶菌株的β-内酰胺酶进行了比较。结果提示:细菌对Ceftazidime耐药后,β-内酰胺酶活性增加13～107倍;这类β-内酰胺酶具有如下特点:(1)水解头孢菌素类强于水解青霉素类;(2)舒巴克坦(5μg/ml)对这类酶无抑制作用,而同等剂量的邻氯青霉素却能明显抑制,(3)pI均≥8.0,与标准质粒介导的β-内酰胺酶的性质不同,符合染色体介导的头孢菌素酶的性质。此外,作者发现pI为8.2或8.4的4株耐药菌的β-内酰胺酶尚未见文献报道。更多还原

【Abstract】 The β-lactamases activities of ceftazidime-resistant strains of E. cloacae and P, aeruginosa were assessed to be 13-107 times stronger than their parent strains measured by UV-260. Among the 12 tested β-lactams, ceftazidime was the most stable one against the hydrolyzation of β-lactamases of 9 ceftazidime-resistant strains(CRS) and 11 standard β-lactamases(SBLM) producing strains. The next successively decreasing order were cefotriaxone, cefuroxime, cefoperazone and cefaman-dole whereas cephalothin and cephaloridine were very liable to be hydrolyzed. The penicillin G, ampicillin, carbenicillin, and cloxacillin were more stable to the β-lac-tamases of CRS than that of SBLM coded by R-plasmid. Sulbactam could significantly inhibit the β-lactamases of SBLM and failed to inhibit those of CRS. However, the latter could be inhibited by cloxacillin. The points of isoelectricity of β-lactama-ses of CRS were measured to be 8. 0. by isoelectric focusing procedure. These results suggested that the characteristics of β-lactamases of CRS were differed from those of the R-plasmid mediated SBLM producing strains and probably belonged to the chromosomal mediated cephalosporinases.更多还原