Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA.
mBio. 2013 Feb 12;4(1):e00023-13. doi: 10.1128/mBio.00023-13.
Uropathogenic Escherichia coli (UPEC) is the most common causative agent of community-acquired urinary tract infection (UTI). In order to cause UTI, UPEC must endure stresses ranging from nutrient limitation to host immune components. RpoS (σ(S)), the general stress response sigma factor, directs gene expression under a variety of inhibitory conditions. Our study of rpoS in UPEC strain CFT073 began after we discovered an rpoS-frameshift mutation in one of our laboratory stocks of "wild-type" CFT073. We demonstrate that an rpoS-deletion mutation in CFT073 leads to a colonization defect during UTI of CBA/J mice at 48 hours postinfection (hpi). There is no difference between the growth rates of CFT073 and CFT073 rpoS in urine. This indicates that rpoS is needed for replication and survival in the host rather than being needed to address limitations imposed by urine nutrients. Consistent with previous observations in E. coli K-12, CFT073 rpoS is more sensitive to oxidative stress than the wild type. We demonstrate that peroxide levels are elevated in voided urine from CFT073-infected mice compared to urine from mock-infected mice, which supports the notion that oxidative stress is generated by the host in response to UPEC. In mice that lack phagocyte oxidase, the enzyme complex expressed by phagocytes that produces superoxide, the competitive defect of CFT073 rpoS in bladder colonization is lost. These results demonstrate that σ(S) is important for UPEC survival under conditions of phagocyte oxidase-generated stress during UTI. Though σ(S) affects the pathogenesis of other bacterial species, this is the first work that directly implicates σ(S) as important for UPEC pathogenesis.
UPEC must cope with a variety of stressful conditions in the urinary tract during infection. RpoS (σ(S)), the general stress response sigma factor, is known to direct the expression of many genes under a variety of stressful conditions in laboratory-adapted E. coli K-12. Here, we show that σ(S) is needed by the model UPEC strain CFT073 to cope with oxidative stress provided by phagocytes during infection. These findings represent the first report that implicates σ(S) in the fitness of UPEC during infection and support the idea of the need for a better understanding of the effects of this global regulator of gene expression during UTI.
尿路致病性大肠杆菌（UPEC）是社区获得性尿路感染（UTI）最常见的病原体。为了引起 UTI，UPEC 必须耐受从营养限制到宿主免疫成分等各种压力。RpoS（σ（S）），一般应激反应σ因子，在各种抑制条件下指导基因表达。我们对 CFT073 菌株中 rpoS 的研究始于我们在实验室中发现一株“野生型”CFT073 的 rpoS 移码突变之后。我们证明，CFT073 中的 rpoS 缺失突变导致 CBA/J 小鼠感染后 48 小时（hpi） UTI 时的定植缺陷。CFT073 和 CFT073 rpoS 在尿液中的生长速度没有差异。这表明 rpoS 是在宿主中复制和存活所必需的，而不是解决尿液营养物质带来的限制所必需的。与先前在大肠杆菌 K-12 中的观察结果一致，CFT073 rpoS 比野生型对氧化应激更敏感。我们证明，与 mock 感染小鼠的尿液相比，来自 CFT073 感染小鼠的尿液中的过氧化物水平升高，这支持了宿主对 UPEC 产生氧化应激的观点。在缺乏吞噬细胞氧化酶的小鼠中，吞噬细胞表达的产生超氧化物的酶复合物，CFT073 rpoS 在膀胱定植中的竞争缺陷丧失。这些结果表明，在 UTI 期间吞噬细胞氧化酶产生的应激下，σ（S）对 UPEC 的存活很重要。虽然 σ（S）影响其他细菌物种的发病机制，但这是首次直接将 σ（S）作为 UPEC 发病机制的重要因素的工作。
UPEC 在感染过程中必须应对尿路感染中多种应激条件。RpoS（σ（S））是一般应激反应σ因子，已知在实验室适应的大肠杆菌 K-12 中，在多种应激条件下指导许多基因的表达。在这里，我们表明模型 UPEC 菌株 CFT073 需要 σ（S）来应对感染期间吞噬细胞提供的氧化应激。这些发现首次表明 σ（S）在感染期间 UPEC 的适应性中起作用，并支持需要更好地了解这种基因表达全局调节剂在 UTI 期间的影响的观点。
