NorB, an Efflux Pump in Staphylococcus aureus Strain MW2, Contributes to Bacterial Fitness in Abscesses
NorB, an Efflux Pump in Staphylococcus aureus Strain MW2, Contributes to Bacterial Fitness in Abscesses
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DOI：
10.1128/jb.00655-08
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发表时间：
2008-11-01
影响因子：
3.2
通讯作者：
Hooper, David C.
中科院分区：
文献类型：
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作者：
Ding, Yanpeng;Onodera, Yoshikuni;Hooper, David C.
虽然金黄色葡萄球菌仍然是医院的一个主要问题，但现在正在社区中传播。MW2菌株(USA400谱系)和其他社区耐甲氧西林金黄色葡萄球菌菌株最常导致皮肤感染并形成脓肿。多药耐药(MDR)外排泵有助于产生抗菌素耐药性，但也可能通过清除环境毒素来促进细菌生存。在金黄色葡萄球菌中，Nora、Norb、NORC和Tet38是染色体编码的外排泵，其过度表达可使多药耐药对喹诺酮类和其他化合物(NOR泵)或仅有四环素(Tet38)产生，但这些泵的天然底物尚不清楚。为了确定这些外排泵在没有抗生素的自然环境中的作用，我们在小鼠皮下脓肿模型中使用了MW2菌株，并比较了逆转录-聚合酶链式反应(RT-PCR)检测的泵基因在脓肿和体外的表达。Norb和te38在体内分别选择性上调171倍和24倍，而Nora和NORC下调。这些变化与MGRA的表达增加有关，MGRA编码一种已知的影响Pump基因表达的转录调节因子。在用Norb或ET38突变体和亲本菌株MW2相同接种量的竞争实验中，每个突变体在体内都表现出大约两到三倍的生长缺陷。在互补实验中，在geh内的attB位点上插入Norb的单拷贝(但不是te38的单拷贝插入)恢复了Norb突变体在体内的生长适合性。我们的发现表明，一些MDR泵，如Norb，当它们在葡萄球菌脓肿中过度表达时，可以促进细菌的生存，并可能有助于脓肿对抗生素治疗的相对耐药性，从而将细菌的适合性和体内的耐药性联系起来。
While remaining a major problem in hospitals, Staphylococcus aureus is now spreading in communities. Strain MW2 (USA400 lineage) and other community methicillin-resistant S. aureus strains most commonly cause skin infections with abscess formation. Multidrug resistance (MDR) efflux pumps contribute to antimicrobial resistance but may also contribute to bacterial survival by removal of environmental toxins. In S. aureus, NorA, NorB, NorC, and Tet38 are chromosomally encoded efflux pumps whose overexpression can confer MDR to quinolones and other compounds (Nor pumps) or tetracyclines alone (Tet38), but the natural substrates of these pumps are not known. To determine the role of these efflux pumps in a natural environment in the absence of antibiotics, we used strain MW2 in a mouse subcutaneous abscess model and compared pump gene expression as determined by reverse transcription-PCR in the abscesses and in vitro. norB and tet38 were selectively upregulated in vivo more than 171- and 24-fold, respectively, whereas norA and norC were down-regulated. These changes were associated with an increase in expression of mgrA, which encodes a transcriptional regulator known to affect pump gene expression. In competition experiments using equal inocula of a norB or tet38 mutant and parent strain MW2, each mutant exhibited growth defects of about two- to threefold in vivo. In complementation experiments, a single-copy insertion of norB (but not a single-copy insertion of tet38) in the attB site within geh restored the growth fitness of the norB mutant in vivo. Our findings indicate that some MDR pumps, like NorB, can facilitate bacterial survival when they are overexpressed in a staphylococcal abscess and may contribute to the relative resistance of abscesses to antimicrobial therapy, thus linking bacterial fitness and resistance in vivo.