Jeong HG, Satchell KJF. Additive function of Vibrio vulnificus MARTX(Vv) and VvhA cytolysins promotes rapid growth and epithelial tissue necrosis during intestinal infection.
PLoS Pathog 2012;
8:e1002581. [PMID:
22457618 PMCID:
PMC3310748 DOI:
10.1371/journal.ppat.1002581]
[Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Accepted: 01/26/2012] [Indexed: 12/18/2022] Open
Abstract
Vibrio vulnificus is a pathogen that causes both severe necrotizing wound infections and life-threatening food-borne infections. Food-borne infection is particularly lethal as the infection can progress rapidly to primary septicemia resulting in death from septic shock and multiorgan failure. In this study, we use both bioluminescence whole animal imaging and V. vulnificus bacterial colonization of orally infected mice to demonstrate that the secreted multifunctional-autoprocessing RTX toxin (MARTXVv) and the cytolysin/hemolysin VvhA of clinical isolate CMCP6 have an important function in the gut to promote early in vivo growth and dissemination of this pathogen from the small intestine to other organs. Using histopathology, we find that both cytotoxins can cause villi disruption, epithelial necrosis, and inflammation in the mouse small intestine. A double mutant deleted of genes for both cytotoxins was essentially avirulent, did not cause intestinal epithelial tissue damage, and was cleared from infected mice by 36 hours by an effective immune response. Therefore, MARTXVv and VvhA seem to play an additive role for pathogenesis of CMCP6 causing intestinal tissue damage and inflammation that then promotes dissemination of the infecting bacteria to the bloodstream and other organs. In the absence of these two secreted factors, we propose that this bacterium is unable to cause intestinal infection in humans.
Vibrio vulnificus causes disease both by infection of wounds from seawater and by consumption of contaminated foods, especially oysters. Wound infection results in necrotizing fasciitis and edema in extremities with mortality of ∼25% as the incidence of septicemia is low. Contaminated food consumption by contrast can lead to highly invasive infections that progress rapidly from an intestinal infection to primary septicemia. Case-fatality rates are ≥50%, with rates as high as 100% in individuals who receive no antibiotic therapy. The aim of this study is to elucidate virulence mechanisms of food-borne infection of the most highly virulent strains of V. vulnificus. We developed a novel intragastric infection model for a highly virulent clinical isolate from Korea in which we can observe the bacterial load in live mice and applied this to study of wild type and strains genetically altered to delete genes for two secreted cytotoxins. Using this model, we show that both the multifunctional-autoprocessing RTX toxin (MARTXVv) and the cytolysin VvhA contribute to rapid in vivo growth of bacteria and that the presence of these factors directly correlates with mouse mortality. These exotoxins are then directly linked to intestinal damage and inflammation.
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