Multidrug resistance pump AcrAB-TolC is required for high-level, Tet(A)-mediated tetracycline resistance in Escherichia coli
Multidrug resistance pump AcrAB-TolC is required for high-level, Tet(A)-mediated tetracycline resistance in Escherichia coli
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DOI：
10.1093/jac/dkl172
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发表时间：
2006-07-01
影响因子：
5.2
通讯作者：
Salomon, Raul A.
中科院分区：
文献类型：
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作者：
de Cristobal, Ricardo E.;Vincent, Paula A.;Salomon, Raul A.
目的：从大肠杆菌TolC突变严重降低Tn10和Tet(A)泵对四环素高度耐药的观察出发，探讨其易感性的机制。方法：测定四环素对MC4100和Tn10的MIC值。通过tet(A)：：LacZ基因融合检测TolC突变对TN10tet(A)表达水平的影响。用荧光分光光度法检测TolC突变对四环素外排和蓄积的影响。结果：Tn 10和质粒编码的Tet(A)使tolC突变株的四环素耐药水平降低5~6倍。荧光分析表明，这是由于TO/C突变体的药物外排减少所致。金霉素耐药性也受到TolC缺失的影响。AcrAB多药外排转运体突变丢失与TolC突变对四环素耐药的影响相同。这表明TolC突变是通过AcrAB系统失活来起作用的。结论：我们的结果与AcrAB泵是大肠杆菌对四环素产生高水平耐药性的重要组成部分的假设是一致的，可能是通过与Tet(A)联合作用。
Objectives: Starting from the observation that Escherichia coli tolC mutations severely reduced the high-level resistance to tetracycline afforded by Tn 10- and plasmid-encoded Tet(A) pumps, we studied the mechanism of this susceptibility.Methods: The MIC of tetracycline for MC4100 to/C::Tn10 and several tolC mutants carrying the Tn10 in other sites on the chromosome (thr:Tn 10) was determined. The effect of a tolC mutation on the level of expression of Tn 10 tet(A) was examined by using a tet(A)::lacZ gene fusion. Influence of tolC mutations on tetracycline efflux and accumulation was quantified by spectrofluorometric assays. The contribution of the AcrAB multidrug efflux system to high-level tetracycline resistance was measured in a Tn 10-carrying acrAB null mutant strain.Results: Tn 10- and plasmid-encoded Tet(A) conferred 5- to 6-fold lower levels of tetracycline resistance in tolC mutants, as compared with control strain tolC(+). Spectrofluorometric analyses showed that this resulted from a decrease in drug efflux in to/Cmutants. Chlortetracycline resistance was also compromised by loss of TolC. Mutational loss of the AcrAB multidrug efflux transporter had the same effect as tolC mutations on tetracycline resistance. This indicated that tolC mutations act through inactivation of the AcrAB system.Conclusions: Our results are compatible with the hypothesis that the AcrAB pump is an important component in the development of high levels of resistance to tetracycline in E. coli, perhaps by working in combination with Tet(A).