2010年CLSI头孢菌素折点改变对产ESBLs奇异变形杆菌药物敏感性结果评估和分析

Evaluation and analysis of the suscepbility interpretation on ESBL-producing Proteus mirabilis according to the changes of cephalosporin breakpoints in CLSI 2010

目的评估2009年CLSI M100-S19及2010年CLSI M100-S20文件中头孢他啶(CAZ)、头孢噻肟(CTX)和头孢唑啉(CFZ)最低抑菌浓度新旧折点变化对产ESBLs奇异变形杆菌药物敏感性试验结果的影响。方法对临床分离33株奇异变形杆菌进行产ESBLs菌株的确证试验,琼脂稀释法检测最低抑菌浓度(MIC),根据药物敏感性结果分别对产ESBLs奇异变形杆菌和非产ESBLs奇异变形杆菌在S19和S20新旧折点下CAZ、CTX和CFZ三种药物的敏感性以及ESBLs阳性菌株分布率进行界定。结果 33株奇异变形杆菌中,产ESBLs菌株6株(18.2%),由旧折点下耐药率50%(CAZ)、50%(CTX)和66.7%(CFZ)分别上升为新折点下66.7%(CAZ)、100%(CTX)和100%(CFZ),敏感率由旧折点下33.3%(CAZ)和50%(CTX)分别下降为新折点下16.7%(CAZ)和0%(CTX),CFZ在新旧折点下均为0,新旧折点标准下药敏结果分布率的差异均有统计学意义。结论对CTX、CFZ,按照CLSI S20新折点琼脂稀释法MICs折点标准判读药敏结果与ESBLs表型检测结果具有高度一致性,临床可以根据药敏结果选择用药,无需进行产ESBLs检测。但对于CAZ,尚需要进一步深入研究和评价。

Objective To evaluate the influences of susceptibility interpretation and distribution of extended-spectrum β-lactamases（ESBLs） producers in Proteus mirabilis according to CLSI 2009（S19） and 2010（S20） breakpoints of ceftazidime（CAZ）,cefotaxime（CTX） and cefazolin（CFZ）.Method ESBLs producers were confirmed by the CLSI phenotypic confirmatory test in 33 clinical isolates of Proteus mirabilis and antimicrobial susceptibility of these isolates were tested by agar dilution method.Antibacterial susceptibility of ESBLs-positive and ESBLs-negative isolates and the distribution of ESBLs producers of the resistant isolates were analyzed according to the breakpoints of S19 and S20.Result ESBLs producers were detected in 18.2%（6/33） of Proteus mirabilis.In ESBLs positive isolates,the resistence rate of CAZ,CTX and CFZ increased from 50.0%,50.0% and 66.7% under S19 to 66.7%,100.0% and 100.0% under S20,respectively.The susceptibility rates decreased from 33.3%,50.0% and 0.0% under S19 to 16.7%,0.0% and 0.0% under S20,respectively.There was a statistically significant difference between the S19 and S20 cephalosporin breakpoints in the distribution of ESBLs producers.Conclusion If use the new CTX and CFZ S20 breakpoints,the concordance of antibacterial susceptibility results and ESBL phenotype will increase greatly.It is no longer necessary to be confirmed by CLSI phenotype confirmatory test.As to CAZ,further evaluation and research is required.