Division of Bacterial and Rickettsial Disease, Department of Wound Infections, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.
J Microbiol. 2012 Jun;50(3):434-43. doi: 10.1007/s12275-012-1555-1. Epub 2012 Jun 30.
Acinetobacter baumannii is a nosocomial bacterial pathogen, and infections attributed to this species are further complicated by a remarkable ability to acquire antimicrobial resistance genes and to survive in a desiccated state. While the antibiotic resistance and biofilm formation of A. baumannii is well-documented, less is known about the virulence attributes of this organism. Recent studies reported A. baumannii strains display a motility phenotype, which appears to be partially dependent upon Type IV pili, autoinducer molecules, and the response to blue light. In this study, we wanted to determine the prevalence of this trait in genetically diverse clinical isolates, and any additional required factors, and environmental cues that regulate motility. When strains are subjected to a wide array of stress conditions, A. baumannii motility is significantly reduced. In contrast, when extracellular iron is provided or salinity is reduced, motility is significantly enhanced. We further investigated whether the genes required for the production of lipopolysaccharide (lpsB) and K1 capsule (epsA/ptk) are required for motility as demonstrated in other Gram-negative bacteria. Transposon mutagenesis resulted in reduced motility by the insertion derivatives of each of these genes. The presence of the parental allele provided in trans, in the insertion mutant background, could only restore motility in the lpsB mutant. The production of core LPS directly contributes to the motility phenotype, while capsular polysaccharide may have an indirect effect. Further, the data suggest motility is regulated by extracellular conditions, indicating that A. baumannii is actively sensing the environment and responding accordingly.
鲍曼不动杆菌是一种医院获得性细菌病原体，其显著的获得抗生素耐药基因的能力和在干燥状态下生存的能力，使得与该物种相关的感染更加复杂。虽然鲍曼不动杆菌的抗生素耐药性和生物膜形成已得到充分证实，但对该生物体的毒力特性知之甚少。最近的研究报告称，鲍曼不动杆菌菌株表现出一种运动表型，这似乎部分依赖于 IV 型菌毛、自诱导分子以及对蓝光的反应。在这项研究中，我们想确定这种特性在遗传上多样化的临床分离株中的流行程度，以及任何额外需要的因素和调节运动的环境线索。当菌株受到广泛的应激条件时，鲍曼不动杆菌的运动能力会显著降低。相比之下，当提供细胞外铁或降低盐度时，运动能力会显著增强。我们进一步研究了产脂多糖（lpsB）和 K1 荚膜（epsA/ptk）所需的基因是否如其他革兰氏阴性菌所示，对运动性是必需的。转座子诱变导致这些基因的每个插入衍生菌株的运动性降低。在插入突变体背景中，亲本等位基因的存在可以仅在 lpsB 突变体中恢复运动性。核心 LPS 的产生直接导致运动表型，而荚膜多糖可能具有间接影响。此外，数据表明运动性受细胞外条件的调节，这表明鲍曼不动杆菌正在积极感知环境并做出相应反应。
