Sixteen Homologs of the Mex-Type Multidrug Resistance Efflux Pump in Bacteroides fragilis
Sixteen Homologs of the Mex-Type Multidrug Resistance Efflux Pump in Bacteroides fragilis
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DOI：
10.1128/aac.49.7.2807-2815.2005
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发表时间：
2005-07
影响因子：
4.9
通讯作者：
O. Ueda;H. Wexler;K. Hirai;Y. Shibata;F. Yoshimura;S. Fujimura
中科院分区：
文献类型：
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作者：
O. Ueda;H. Wexler;K. Hirai;Y. Shibata;F. Yoshimura;S. Fujimura
摘要通过同源性检索，在脆弱拟杆菌（Bacteroides fragilis）基因组序列中发现了耐药-结瘤-细胞分裂（RND）家族多药外排泵操作子的16个同源物。与铜绿假单胞菌最相似的4个基因的mexB同源物产生了破坏突变体。逆转录pcr结果表明，该基因以多顺反子方式转录，启动子位于bmeA （mexA同源物）的上游。其中一个突变体（在bmeB中，mexB同源物）比亲本菌株对某些头孢菌素、多肽抗生素、夫西地酸、新生物霉素和嘌呤霉素更敏感。该同源基因和邻近的上游基因bmeA在一个过敏的大肠杆菌宿主中被克隆。由此产生的携带脆弱芽孢杆菌bmeAB的转化子对某些药剂具有更强的抗性；这些制剂对脆弱芽孢杆菌bmeB破坏突变体的mic也低于亲本菌株。假定的外排泵操纵子由bmeA、bmeB和bmeC（假定的与OprM同源的外膜通道蛋白）组成。外排泵抑制剂羰基氰化物间氯苯肼（一种消除能量源的质子导体）和ph - arg β-萘酰胺（MC-207,110）（铜绿假单胞菌RND泵的第一个特异性抑制剂）的加入，导致亲本菌株的mic降低，但在bmeB中断突变体中没有，表明bmeB泵受到这些抑制剂的影响。这是第一次描述RND型泵在拟杆菌属。
ABSTRACT Sixteen homologs of multidrug resistance efflux pump operons of the resistance-nodulation-cell division (RND) family were found in the Bacteroides fragilis genome sequence by homology searches. Disruption mutants were made to the mexB homologs of the four genes most similar to Pseudomonas aeruginosa mexB. Reverse transcription-PCR was conducted and indicated that the genes were transcribed in a polycistronic fashion and that the promoter was upstream of bmeA (the mexA homolog). One of these disruption mutants (in bmeB, the mexB homolog) was more susceptible than the parental strain to certain cephems, polypeptide antibiotics, fusidic acid, novobiocin, and puromycin. The gene for this homolog and the adjacent upstream gene, bmeA, were cloned in a hypersensitive Escherichia coli host. The resultant transformants carrying B. fragilis bmeAB were more resistant to certain agents; these agents also had lower MICs for the B. fragilis bmeB disruption mutants than for the parental strain. The putative efflux pump operon is composed of bmeA, bmeB, and bmeC (a putative outer membrane channel protein homologous with OprM). Addition of the efflux pump inhibitors, carbonyl cyanide m-chlorophenylhydrazone (a proton conductor that eliminates the energy source) and Phe-Arg β-naphthylamide (MC-207,110) (the first specific inhibitor described for RND pumps in P. aeruginosa), resulted in lowered MICs in the parental strain but not in the bmeB disruption mutant, indicating that the bmeB pump is affected by these inhibitors. This is the first description of RND type pumps in the genus Bacteroides.