BACKGROUNDVibrio vulnificus (Vv) is an estuarine bacterium that can cause primary septicemia as well as serious wound infections. However, little is known about the mechanisms by which Vv infects dendritic cells (DCs) and its effects on cytoskeleton. In this study, we aimed to investigate the invasion, internalization, and the organelles damage of the cultured dendritic cells (a DC 2.4 strain) during Vv infection.

METHODSThe study model was the cultured DCs infected by a Vv 1.758 strain. Electron microscopy was used to observe the localization of bacteria at the different time points of infection, cell morphology, and the process of organelles changes. The cytoskeleton structure including the microfilaments and the microtubules rearrangement was examined under a fluorescence microscope.

RESULTSThe Vv were pinocytosised into the DC cells through double-sides, and localized at 1 - 2 mm of the inner side membrane. It took 1.3, 1.9, and 3.4 hours to reach the infection ratio of 25%, 50%, and 75%, respectively. Using electron microscopy, the DCs had been observed to have developed chromatin aggregation within 4.0 hours, and significant cytoskeleton structure disruption was noted within 6.0 hours.

CONCLUSIONThe high lethality of Vv infection may be associated with the direct disruption of the DCs cytoskeleton structure.

Animals ; Apoptosis ; physiology ; Cells, Cultured ; Cytoskeleton ; metabolism ; ultrastructure ; DNA Fragmentation ; Dendritic Cells ; metabolism ; microbiology ; ultrastructure ; Mice ; Microscopy, Electron ; Microscopy, Electron, Transmission ; Vibrio Infections ; metabolism ; Vibrio vulnificus ; pathogenicity

We identified 6 sucrose-fermenting Vibrio vulnificus strains and examined their virulence characteristics. They were all encapsulated, motile, capable of producing toxins and utilizing transferrin-bound iron, cytotoxic to cultured cells, and virulent enough to kill mice. They could be definitely identified only by genetic identification methods such as PCR, and not by conventional culture-based identification methods such as API 20E (bioMerieux, France). These results indicate that it is essential to adopt genetic approaches as early as possible in order to avoid misdiagnosis of such strains, especially in clinical situations.
Animals ; Bacterial Proteins/genetics ; Fermentation ; Mice ; RNA, Ribosomal, 16S/genetics ; Sequence Analysis, DNA ; Sucrose/*metabolism ; Vibrio vulnificus/genetics/growth & development/*pathogenicity ; Virulence

Lipoprotein plays a role in the host defense against bacterial infection, and its serum level has been demonstrated to be an important prognosis factor of survival. We have previously demonstrated that LDL directly inactivates the hemolytic activity of Vibrio vulnificus cytolysin (VVC) in vitro. The object of this study was therefore to examine whether the LDL-mediated inactivation of VVC leads to protection against lethal infection of V. vulnificus in vivo, using wild and VVC-deficient V. vulnificus strains. Unexpectedly, we found that LDL protects mouse lethality induced by VVC-deficient as well as wild V. vulnificus strain. We also demonstrated that LDL blocks V. vulnificus LPS-induced lethality in mice. These results suggest that LDL preferentially act on endotoxin rather than exotoxin in the protection against V. vulnificus-induced mice lethality.
Animals ; Disease Models, Animal ; Female ; Humans ; Lipopolysaccharides/*antagonists & inhibitors ; Lipoproteins, LDL/*pharmacology ; Mice ; Mice, Inbred ICR ; Perforin/antagonists & inhibitors/genetics ; Vibrio Infections/prevention & control ; Vibrio vulnificus/*drug effects/genetics/*pathogenicity ; Virulence/drug effects/genetics/physiology

Vibrio vulnificus cytolysin forms transmembrane pores that are permeable to calcium ions in pulmonary endothelial cells, and has been suggested as an important virulence factor that sequestrate neutrophils primarily in the lung. To elucidate the mechanism we investigated whether the cytolysin affect the expression of endothelial P-selectin and adhesiveness of pulmonary endothelial cells for neutrophils. The cytolysin increased the adhesiveness of CPAE cell, a pulmonary endothelial cell line, for neutrophils in a concentrationand time-dependent manner. The increase of adhesiveness occurred within several minutes after the cytolysin exposure, persisted up to 90 min, and was not affected by cycloheximide. Furthermore, flow cytometric analyses showed that cytolysin enhanced the level of P-selectin on CPAE cell surface. Therefore, these results suggest that the cytolysin-induced hyperadhesiveness of pulmonary endothelial cells for neutrophils is mediated by the mobilization of endothelial P-selectin to the cell surface.
Animals ; Cattle ; Cell Adhesion/*drug effects ; Cell Line ; Cycloheximide/pharmacology ; Cytotoxins/*toxicity ; Dose-Response Relationship, Drug ; Endothelium, Vascular/cytology/*drug effects/metabolism ; Kinetics ; Neutrophils/*drug effects/pathology ; P-Selectin/*metabolism ; Protein Synthesis Inhibitors/pharmacology ; Pulmonary Artery/cytology/*drug effects/metabolism ; Rats ; Vibrio Infections/etiology/pathology ; Vibrio vulnificus/*pathogenicity

Vibrio vulnificus cytolysin forms transmembrane pores that are permeable to calcium ions in pulmonary endothelial cells, and has been suggested as an important virulence factor that sequestrate neutrophils primarily in the lung. To elucidate the mechanism we investigated whether the cytolysin affect the expression of endothelial P-selectin and adhesiveness of pulmonary endothelial cells for neutrophils. The cytolysin increased the adhesiveness of CPAE cell, a pulmonary endothelial cell line, for neutrophils in a concentrationand time-dependent manner. The increase of adhesiveness occurred within several minutes after the cytolysin exposure, persisted up to 90 min, and was not affected by cycloheximide. Furthermore, flow cytometric analyses showed that cytolysin enhanced the level of P-selectin on CPAE cell surface. Therefore, these results suggest that the cytolysin-induced hyperadhesiveness of pulmonary endothelial cells for neutrophils is mediated by the mobilization of endothelial P-selectin to the cell surface.
Animals ; Cattle ; Cell Adhesion/*drug effects ; Cell Line ; Cycloheximide/pharmacology ; Cytotoxins/*toxicity ; Dose-Response Relationship, Drug ; Endothelium, Vascular/cytology/*drug effects/metabolism ; Kinetics ; Neutrophils/*drug effects/pathology ; P-Selectin/*metabolism ; Protein Synthesis Inhibitors/pharmacology ; Pulmonary Artery/cytology/*drug effects/metabolism ; Rats ; Vibrio Infections/etiology/pathology ; Vibrio vulnificus/*pathogenicity