TEM-1 β-lactamase as a source of resistance to sulbactam in clinical strains of Acinetobacter baumannii
TEM-1 β-lactamase as a source of resistance to sulbactam in clinical strains of Acinetobacter baumannii
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DOI：
10.1093/jac/dkt275
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发表时间：
2013-12-01
影响因子：
5.2
通讯作者：
Nemec, Alexandr
中科院分区：
文献类型：
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作者：
Krizova, Lenka;Poirel, Laurent;Nemec, Alexandr
目的：众所周知舒巴坦对鲍曼不动杆菌具有临床相关的内在活性。虽然长期以来在不动杆菌中对这种药物的继发性耐药性一直有报道，但实际上对其分子基础一无所知。本研究的目的是检验β-内酰胺酶TEM-1与A.方法：17株临床分离的鲍曼不动杆菌。选择鲍曼不动杆菌以代表对舒巴坦的定量敏感性和分子分型特征的不同组合。通过PCR筛选菌株中bla（TEM-1）基因及其变体的存在。对包含bla（TEM）基因（包括其启动子）的扩增子进行测序。使用半定量实时PCR评估bla（TEM）基因的表达和拷贝数。将bla（TEM-1）基因转入敏感的A.结果：10株细菌携带bla（TEM-1），MIC>= 8.0mg/L，1株MIC为2 mg/L，其余10株细菌携带bla（TEM-19），MIC为1 mg/L。bla（TEM-1）表达水平与舒巴坦的MIC呈正相关（r=0.92）。启动子P4在所有菌株中与bla（TEM）基因连锁，除了携带P3的菌株（MIC为2 mg/L）。易感A. TEM-1菌株对舒巴坦的MIC增加了64倍，对替卡西林和哌拉西林产生耐药性，但对广谱头孢菌素、氨曲南和碳青霉烯类抗生素的敏感性没有改变。鲍曼不动杆菌。
Objectives: Sulbactam is well known to have clinically relevant intrinsic activity against Acinetobacter baumannii. Although secondary resistance to this drug has long been reported in acinetobacters, virtually nothing is known about its molecular basis. The aim of this study was to test the hypothesis that beta-lactamase TEM-1 is responsible for sulbactam resistance in A. baumannii.Methods: Seventeen clinical strains of A. baumannii were selected to represent different combinations of quantitative susceptibilities to sulbactam and molecular typing characteristics. The strains were screened by PCR for the presence of the bla(TEM-1) gene and its variants. Amplicons encompassing the bla(TEM) genes, including their promoters, were sequenced. The expression and copy number of the bla(TEM) genes were assessed using semi-quantitative real-time PCR. Transfer of the bla(TEM-1) gene into a susceptible A. baumannii strain was achieved by electroporation.Results: Six strains were negative for the bla(TEM) gene and had sulbactam MICs of 0.5-1.0 mg/L, 10 strains harboured bla(TEM-1) and showed MICs >= 8.0 mg/L, except for one strain with an MIC of 2 mg/L, while the remaining strain carried bla(TEM-19) and had an MIC of 1 mg/L. The level of bla(TEM-1) expression positively correlated with the MICs of sulbactam (r=0.92). Promoter P4 was linked to the bla(TEM) gene in all strains except for a P3-carrying strain (an MIC of 2 mg/L). Transformation of the susceptible A. baumannii strain with bla(TEM-1) resulted in a 64-fold increase in sulbactam MIC and in resistance to ticarcillin and piperacillin, but no change in susceptibility to broad-spectrum generation cephalosporins, aztreonam or carbapenems.Conclusions: The results presented suggest that TEM-1 represents a clinically relevant mechanism of sulbactam resistance in A. baumannii.