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Evidence for the translocation of Enterococcus faecalis across the mouse intestinal tract
C L Wells1, R P Jechorek, S L Erlandsen
1Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis 55455.
Abstract:
The pathogenesis of Enterococcus (Streptococcus) faecalis was studied in mice with E. faecalis intestinal overgrowth (10(9) - 10(10) per gram of cecum) induced by metronidazol and streptomycin treatment coupled with oral inoculation of E. faecalis. E. faecalis was recovered from the mesenteric lymph nodes, liver, and spleen; mortality was noted in 8 (13%) of 62 mice after 14 days of E. faecalis intestinal overgrowth. Light, immunofluorescent, and electron (scanning and transmission) microscopy of ileal tissue was used in an attempt to localize E. faecalis translocating across intestinal tissue. Dense coccal bacteria were observed in the intestinal lumen, and the epithelium appeared intact. Coccal bacteria were observed adherent to the microvillus border of the entire villous epithelium, including the deeper regions of the intestinal crypts. Immunofluorescence localized E. faecalis within columnar epithelial cells, lamina propria, submucosa, and muscularis externa (including the lumen of small vessels). Transmission electron microscopy localized coccal bacteria within vacuoles in the cytoplasm of intact epithelial cells. These results indicated that E. faecalis could translocate across an intact intestinal tract and cause systemic infection and death. In this model, the intestinal epithelial cell appeared to be a portal of entry in the pathogenesis of systemic E. faecalis infection.
Insights
Enterococcus faecalis intestinal overgrowth in mice demonstrated translocation across an intact gut. Intestinal epithelial cells served as the entry point for systemic infection and mortality in this study.
Area of Science:
- Microbiology
- Pathogenesis
- Gastroenterology
Background:
- Enterococcus faecalis is an opportunistic pathogen.
- Intestinal overgrowth can lead to systemic infections.
- The translocation mechanism of E. faecalis across the intestinal barrier is not fully understood.
Purpose of the Study:
- To investigate the pathogenesis of Enterococcus faecalis-induced intestinal overgrowth in a murine model.
- To determine if E. faecalis can translocate across an intact intestinal barrier.
- To identify the portal of entry for systemic E. faecalis infection.
Main Methods:
- Induction of E. faecalis intestinal overgrowth in mice using antibiotic treatment and oral inoculation.
- Recovery of E. faecalis from systemic organs (mesenteric lymph nodes, liver, spleen).
- Microscopic examination (light, immunofluorescence, electron microscopy) of ileal tissue to visualize bacterial translocation.
Main Results:
- E. faecalis intestinal overgrowth was successfully established (10(9) - 10(10) CFU/g).
- E. faecalis was recovered from mesenteric lymph nodes, liver, and spleen, with 13% mortality.
- Microscopy revealed E. faecalis adherence to the intestinal epithelium and intracellular localization within epithelial cells, suggesting translocation across an intact barrier.
Conclusions:
- Enterococcus faecalis can translocate across an intact intestinal tract.
- Intestinal epithelial cells serve as a portal of entry for systemic E. faecalis infection.
- This murine model provides insights into the pathogenesis of systemic E. faecalis infections originating from the gut.