A small-molecule inhibitor of the bacterial type III secretion system protects against in vivo infection with Citrobacter rodentium

Abstract

The type III secretion system (T3SS) is highly conserved in many Gram-negative pathogenic bacteria and functions as an injector of bacterial proteins (effectors) into host cells. T3SSs are involved in establishing disease processes, but this machinery is not essential for bacterial growth or homeostasis. Thus, T3SS is expected to be a candidate therapeutic target, and inhibitors of T3SSs could potentially reduce virulence without causing bacterial death, thereby avoiding any subsequent development of resistance. We identified a linear polyketide compound, aurodox, as a specific T3SS inhibitor from the culture broth of Streptomyces sp. using a screening system for the T3SS-mediated hemolysis of enteropathogenic Escherichia coli (EPEC) established by our group. Aurodox strongly inhibited T3SS-mediated hemolysis with an IC 50 value of 1.5 lg ml À1 without affecting bacterial growth in liquid media. We also demonstrated that aurodox specifically inhibits the secretion of type IIIsecreted proteins such as EspB, EspF and Map, without affecting the expression of the housekeeping protein GroEL. Furthermore, an in vivo infection study using mice clearly indicated that the administration of aurodox allowed the mice to survive a lethal dose of Citrobactor rodentium, a model bacterium for human pathogens such as EPEC. Thus, our in vivo study directly demonstrated for the first time that this putative T3SS inhibitor can be applied as a novel class of anti-infective agents.

An NF-κB-Based High-Throughput Screen Identifies Piericidins as Inhibitors of the Yersinia pseudotuberculosis Type III Secretion System

“…This hit rate is within the range of previously published T3SS inhibitor screens (16)(17)(18)(19)(20)(21).…”

“…6 to validate our HTS results (16). Two other studies by Iwatsuki et al and Kimura et al published HTSs analyzing host-pathogen interactions with anucleate cells, measuring T3SS-mediated red blood cell lysis (21,33). One major advantage of the HTS presented here is the use of a relatively low MOI of 7.…”

“…3C; see Fig. S4 in the supplemental material) (21). This moiety is relatively rare in nature, and it is tempting to speculate that these compounds may share a molecular target.…”

Role of F1C Fimbriae, Flagella, and Secreted Bacterial Components in the Inhibitory Effect of Probiotic Escherichia coli Nissle 1917 on Atypical Enteropathogenic E. coli Infection

“…It has previously been shown that a low-molecular-weight polyketide compound isolated from cultures of Streptomyces sp. was able to inhibit the T3SS (63). However, there are no data available on whether and how probiotics might block the T3SS.…”

Cytosporone B, an Inhibitor of the Type III Secretion System of Salmonella enterica Serovar Typhimurium

“…T he type III secretion system (T3SS) is a highly specialized virulent protein nano-injector, which traverses the cell wall of Gram-negative bacteria and transports effector proteins from bacterial cytoplasm into eukaryotic host cells to facilitate bacterial invasion and dissemination (1,2). As an important virulence factor, T3SS is highly conserved in structure and function among different Gram-negative bacteria (3)(4)(5), such as Salmonella spp., Yersinia spp., Shigella spp., Pseudomonas spp., enteropathogenic Escherichia coli (EPEC), enterohemorrhagic E. coli (EHEC), Chlamydia spp., and Burkholderia spp., and some specific plant-pathogenic bacteria, Erwinia spp., Xanthomonas campestris, Ralstonia solanacearum, and Rhizobium spp.…”