Light and Electron Microscopic Study on the Invasion by Vibrio vulnificus to the Ileal Epithelium of Rats

Kim, Hyoung Tae

Abstract

Vibrio vulnificus (VV) is known to cause the wound infection, primary septicemia, gastroenteritis and other infection. The reports about the gastroenteritis by VV are very rare, and especially the mechanism of the invasion into the intestinal epithelium by VV is not known. In the present study, the rat ileum injected locally and directly with VV for 5, 30, 60, 120 minutes were examined by light, scanning and transmission electron microscopy. By scanning electron microscopy, VV were found on the surfaces of absorptive cells, goblet cells, and M (microfold) cells after incubation of 5 minutes. Microvilli of the epithelial cells were lost partially after incubation of 30 minutes. Microvilli of many epithelial cells were lost, and VV invaded vertically into the epithelial cell after incubation of 60 and 120 minutes. By light and transmission electron microscopy, VV attached and invaded by various degree into the epithelial cells after incubation of 30 minutes. Microvilli of luminal surface of the epithelial cell were lost partially and invaginated at the portion that VV contacted. Rich microfilaments were assembled just below its invaginated luminal membrane of the epithlial cell and represented 500 nm thick band. Electron-dense dark band, 30~90 nm, was found between VV and the invaginated luminal surface of the epithelial cell. At 60 minutes after injection, the luminal surface of some epithelial cells showed the loss of microvilli and the irregular structures protruding into the lumen. At 120 minutes after injection, the damage of the epithelial cells was prominent and extensive. In relation to VV, microvilli of the epithelial cells were lost and protruded as bleb-like or irregular structures. Luminal plasma membranes of many epithelial cells were ruptured, through which cell organelles and inclusions discharged into the lumen. VV were found within the damaged epithelial cell as well as in the defective intercellular space of the epithelium. These results suggested that the early mechanisms of the invasion into the epithelium of rat ileum by VV are endocytosis and cytolysis.