Department of Infection Biology, London School of Hygiene and Tropical Medicine , London, United Kingdom.
Department of Infectious Diseases, Central Clinical School, Monash University , Melbourne, Victoria, Australia.
mBio. 2023 Aug 31;14(4):e0088223. doi: 10.1128/mbio.00882-23. Epub 2023 May 31.
Enteroinvasive (EIEC) and are closely related agents of bacillary dysentery. It is widely viewed that EIEC and species evolved from via independent acquisitions of a large virulence plasmid (pINV) encoding a type 3 secretion system (T3SS). Sequence Type (ST)99 O96:H19 is a novel clone of EIEC responsible for recent outbreaks in Europe and South America. Here, we use 92 whole genome sequences to reconstruct a dated phylogeny of ST99 , revealing distinct phylogenomic clusters of pINV-positive and -negative isolates. To study the impact of pINV acquisition on the virulence of this clone, we developed an EIEC-zebrafish infection model showing that virulence of ST99 EIEC is thermoregulated. Strikingly, zebrafish infection using a T3SS-deficient ST99 EIEC strain and the oldest available pINV-negative isolate reveals a separate, temperature-independent mechanism of virulence, indicating that ST99 non-EIEC strains were virulent before pINV acquisition. Taken together, these results suggest that an already pathogenic acquired pINV and that virulence of ST99 isolates became thermoregulated once pINV was acquired. IMPORTANCE Enteroinvasive (EIEC) and are etiological agents of bacillary dysentery. Sequence Type (ST)99 is a clone of EIEC hypothesized to cause human disease by the recent acquisition of pINV, a large plasmid encoding a type 3 secretion system (T3SS) that confers the ability to invade human cells. Using Bayesian analysis and zebrafish larvae infection, we show that the virulence of ST99 EIEC isolates is highly dependent on temperature, while T3SS-deficient isolates encode a separate temperature-independent mechanism of virulence. These results indicate that ST99 non-EIEC isolates may have been virulent before pINV acquisition and highlight an important role of pINV acquisition in the dispersal of ST99 EIEC in humans, allowing wider dissemination across Europe and South America.
肠侵袭性（EIEC）和痢疾志贺菌是密切相关的细菌性痢疾病原体。人们普遍认为，EIEC 和志贺菌通过独立获得编码 III 型分泌系统（T3SS）的大型毒力质粒（pINV）从志贺菌进化而来。ST99 血清型 O96:H19 是肠侵袭性EIEC 的一个新克隆，负责最近在欧洲和南美洲的暴发。在这里，我们使用 92 个全基因组序列来重建 ST99 的时间校准系统发育树，揭示了 pINV 阳性和阴性分离株的明显系统基因组簇。为了研究 pINV 获得对该克隆毒力的影响，我们开发了一种 EIEC-斑马鱼感染模型，表明 ST99 EIEC 的毒力受体温调节。引人注目的是，使用 T3SS 缺陷型 ST99 EIEC 菌株和最早获得的 pINV 阴性分离株进行斑马鱼感染表明存在另一种独立的、与温度无关的毒力机制，表明在获得 pINV 之前，ST99 非 EIEC 菌株就具有毒力。总之，这些结果表明，一种已经具有致病性的志贺菌获得了 pINV，并且一旦获得 pINV，ST99 分离株的毒力就变得受体温调节。重要性肠侵袭性（EIEC）和痢疾志贺菌是细菌性痢疾的病原体。序列型（ST）99 是 EIEC 的一个克隆，据推测，它通过最近获得编码 III 型分泌系统（T3SS）的大型质粒 pINV 导致人类疾病，该 T3SS 赋予了侵袭人类细胞的能力。使用贝叶斯分析和斑马鱼幼虫感染，我们表明 ST99 EIEC 分离株的毒力高度依赖于温度，而 T3SS 缺陷型分离株则编码一种独立的、与温度无关的毒力机制。这些结果表明，在获得 pINV 之前，ST99 非 EIEC 分离株可能具有毒力，并且强调了 pINV 获得在 ST99 EIEC 在人类中的传播中的重要作用，使其能够在欧洲和南美洲更广泛地传播。
