【摘要】 目的了解革兰阴性杆菌对阿莫西林的耐药机制,探讨MIC与β-内酰胺酶活性之间的相关性。方法收集2003年2月至2004年1月全院分离出的耐阿莫西林革兰阴性杆菌73株,琼脂二倍稀释法测定阿莫西林MIC;超声破碎法提取β-内酰胺酶;对β-内酰胺酶进行定性检测和活性测定。结果13.7%的革兰阴性杆菌MIC≤1024μg/ml,86.3%的革兰阴性杆菌MIC>1024μg/ml;酶活性<1000U、1000~10000U、>10000U的细菌分别为53.42%,41.10%和5.48%;大肠埃希菌、阴沟肠杆菌、铜绿假单胞菌、鲍曼不动杆菌及其它革兰阴性杆菌的酶活性中位数分别为1343.32、1584.71、301.675、256.41和984.33U(Kruskal-WallisH检验,P<0.05)。结论革兰阴性杆菌对阿莫西林多呈高度耐药,且主要为大肠埃希菌、阴沟肠杆菌、铜绿假单胞菌、鲍曼不动杆菌;耐药阴沟肠杆菌和大肠埃希菌的酶活性明显高于铜绿假单胞菌和鲍曼不动杆菌;酶活性和MIC之间没有必然的正相关关系,提示革兰阴性杆菌对阿莫西林耐药系多种机制共同参与的结果。更多还原

【Abstract】 Objective To investigate amoxicillin resistance mechanism of Gram-negative bacilli and analyze the correlation between β-lactamase activity and MIC of amoxicillin. Method Seventy-three amoxicillin-resistant strains of Gram-negative bacilli were isolated from the Affiliated Hospital of North Sichuan Medical College from February 2003 to January 2004. MICs of amoxicillin were determined by two-fold agar dilution method. Crude β-lactamase preparations were obtained by sonication. The enzyme activities were determined by ultraviolet spectrophotometry. Result There were 13.7% of Gram-negative bacilli with MICs≤1024μg/ml and 86.3% of Gram-negative bacilli with MICs>1024μg/ml. The Gram-negative bacilli with enzyme activities <1000U (low level) was 53.42%; 1000～10000U (median level) 41.10% and >10000U (high level) 5.48%. As for Escherichia coli, Enterobacter cloacae, Pseudomonas aeruginosa, Acinetobacter baumannii and other Gram-negative bacilli, the median enzyme activities were 1343.32U, 1584.71U, 301.675U, 256.41U and 984.33U, respectively. And enzyme activities had a difference among the four species by applying Kruskal-Wallis H test (P<0.05). Conclusion Most of Gram-negative bacilli including Escherichia coli, Enterobacter cloacae, Pseudomonas aeruginosa and Acinetobacter baumannii were high level amoxicillin resistant. All isolates produced β-lactamase. The enzyme activities of Enterobacter cloacae and Escherichia coli were the highest and those of Pseudomonas aeruginosa and Acinetobacter baumannii were the lowest. Multiple mechanisms contributed to Gram-negative bacilli amoxicillin resistance, enzyme activity and MIC had no apparent correlation, however, in some bacteria genera or species the enzyme activity and MIC had a positive correlation trend within the certain range of MIC.更多还原