Morphology of Intestinal Colonization of Yersinia enterocolitica Serovar O3 in Mice.

Abstract

ABSTRACT. The present study was made to know the morphology of the initial invasion and lesions involved in the intestinal colonization of Yersinia enterocolitica serovar O3 in the epithelium of Peyer's patches of mice. Microfold (M) cells formed a specific structure like a pseudopodium and the bacteria were observed on the surface of the pseudopodium-like structure 4 hr after oral administration of serovar O3. The colonies of serovar O3 were observed in the epithelium and the lamina propria of the Peyer's patches dome region, and the bacteria grown in the Peyer's patches were in direct contact with the lumen without covered with the host tissue 24 hr after the administration.-KEY WORDS: M cell, Peyer's patch, Yersinia enterocolitica.J. Vet. Med. Sci. 61(10): 1171-1173, 1999 The sections were allowed to react at room temperature for an hour with anti-O3 rabbit sera made in our laboratory, washed three times with PBS, then treated with peroxidaselabelled anti-rabbit IgG-goat antibody (KPL) at room temperature for an hour. The sections were fixed with 1% glutaraldehyde, washed three times with PBS and treated with 0.05 M tris buffer pH 7.6 containing 0.04% 3,3'-diamino-benzidine and 0.005% H 2 O 2 for 10 min. Counter-staining was made with a 1% methyl green solution. The sections were dehydrated and observed under an optical microscope according to the routine methods.Specimens for a scanning electron microscopy were obtained by the same method of the optical microscopy as described above. The specimens obtained were fixed with glutaraldehyde and osmic acid. They were washed, dehydrated through a graded series of ethanol, and transferred to isoamylacetate. After critical-point drying, the specimens were coated with gold with an ion sputtering apparatus and observed under a scanning electronmicroscope (JEOL T330A) at 15 kV.Although small colonies were observed in the subepithelial region 8 hr after oral administration as shown in Fig. 1A, no such colonies were found in the sections obtained from specimens 4 hr after oral administration.The colonies of serovar O3 were observed in the epithelium and the lamia propria of only the dome area in the Peyer's patches. No colonies were observed in the regions of the intestinal villi or the center of Peyer's patches as shown in Fig. 1B. Figure 2A shows the surface of the dome region of Peyer's patches of the small intestines 4 hr after oral administration, a structure like a pseudopodium formed from the microfold (M) cells was observed and the bacteria were seen on the surface of the pseudopodium-like structure. M cells in the control mice on the other hand, were forming nothing like a pseudopodium (Fig. 2B). Figure 3 shows that the epithelium of the dome has been destroyed 24 hr after oral administration due to the growth of serovar O3. The bacteria forming colonies were seen without covered with the cell membrane or other substance of the host tissue. The bacteria were in direct contact with Yersinia enterocolitica is an agent of human gastroenteritis. Experimental infecti...