Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA.
Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA
Infect Immun. 2021 Mar 17;89(4). doi: 10.1128/IAI.00716-20.
Uropathogenic (UPEC), the primary etiologic agent of urinary tract infections (UTIs), encounters a restrictive population bottleneck within the female mammalian bladder. Its genetic diversity is restricted during establishment of cystitis because successful UPEC must invade superficial bladder epithelial cells prior to forming clonal intracellular bacterial communities (IBCs). In this study, we aimed to understand UPEC population dynamics during ascending pyelonephritis, namely, formation of kidney bacterial communities (KBCs) in the renal tubular lumen and nucleation of renal abscesses. We inoculated the bladders of both male and female C3H/HeN mice, a background which features vesicoureteral reflux; we have previously shown that in this model, males develop severe, high-titer pyelonephritis and renal abscesses much more frequently than females. Mice were infected with 40 isogenic, PCR-tagged ("barcoded") UPEC strains, and tags remaining in bladder and kidneys were ascertained at intervals following infection. In contrast to females, males maintained a majority of strains within both the bladder and kidneys throughout the course of infection, indicating only a modest host-imposed bottleneck on overall population diversity during successful renal infection. Moreover, the diverse population in the infected male kidneys obscured any restrictive bottleneck in the male bladder. Finally, using RNA hybridization following mixed infections with isogenic UPEC bearing distinct markers, we found that despite their extracellular location (in the urinary space), KBCs are clonal in origin. This finding indicates that even with bulk reflux of infected bladder urine into the renal pelvis, successful ascension of UPEC to establish the tubular niche is an uncommon event.
尿路致病性大肠杆菌（UPEC）是尿路感染（UTI）的主要病原体，在雌性哺乳动物的膀胱中遇到了一个受限的种群瓶颈。在膀胱炎的形成过程中，其遗传多样性受到限制，因为成功的 UPEC 必须在形成克隆细胞内细菌群落（IBC）之前侵入浅表膀胱上皮细胞。在这项研究中，我们旨在了解 UPEC 在肾盂肾炎上升过程中的种群动态，即在肾小管腔内形成肾脏细菌群落（KBC）和肾脏脓肿的形成。我们将膀胱接种于雄性和雌性 C3H/HeN 小鼠，该背景下存在输尿管反流；我们之前已经表明，在这种模型中，雄性比雌性更频繁地发展为严重、高滴度的肾盂肾炎和肾脏脓肿。将 40 个同源、PCR 标记（“条形码”）的 UPEC 菌株感染给小鼠，并在感染后不同时间确定膀胱和肾脏中残留的标记。与雌性不同，雄性在感染过程中始终在膀胱和肾脏中保留大多数菌株，这表明在成功的肾脏感染过程中，宿主对整体种群多样性的限制瓶颈仅适度。此外，感染雄性肾脏中多样化的种群掩盖了雄性膀胱中任何限制瓶颈。最后，使用混合感染具有不同标记的同源 UPEC 后进行 RNA 杂交，我们发现，尽管它们位于细胞外（在尿空间），但 KBC 起源于克隆。这一发现表明，即使有受感染的膀胱尿液的大量反流进入肾盂，UPEC 成功上升到建立肾小管小生境也是一个罕见的事件。
