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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Food Safety and Enteric Pathogens Research » Research » Publications at this Location » Publication #128039
Title: SEGMENTED FILAMENTOUS BACTERIA INTERACT WITH INTRAEPITHELIAL MONONUCLEAR CELLS

Author
item MEYERHOLZ, D - IOWA STATE UNIVERSITY
item STABEL, THOMAS
item CHEVILLE, N - IOWA STATE UNIVERSITY

Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: In the human population, it is estimated that there are over 2 million cases of nontyphoid salmonellosis in the United States per year at a cost approaching $1.4 billion. In addition to the economic impact of salmonellosis on the human population, it is a major economic disease of swine and resulting in millions of dollars in lost income to the swine industry. Segmented filamentous bacteria (SFB) are harmless bacteria that colonize the small intestine of a wide range of species. In swine, the SFB are most visible soon after weaning and disappear weeks later. The disappearance of SFB coincides with the time of mucosal immune activation and it is believed that SFB may be important in this initial general stimulation of the immune system. The mechanism by which the bacteria interact with the porcine immune system has not been well defined. Porcine intestinal samples were prepared for electron microscopy. Results showed SFB attachment to and indentation of the apical cell membrane. In addition, SFB were seen extended into intimate association with intraepithelial mononuclear cells (without penetration of the mononuclear cell membrane). In conclusion, we provide morphological evidence of direct interaction between SFB and immune cells of the gut. A better understanding of the relationship between normal gut microbes such as SFB and infectious bacteria such as Salmonella will allow new and improved prevention strategies for salmonellosis in swine. Eventual beneficiaries are the American consumer since new intervention strategies for salmonellosis will allow a continued supply of inexpensive, wholesome pork and pork products.

Technical Abstract: Segmented filamentous bacteria (SFB) are autochthonus bacteria that colonize the small intestine of a wide range of species. SFB are generally considered nonpathogenic and host specific. These bacteria are suggested to function as an important microbial component of the gastrointestinal ecosystem in swine. The SFB are most visible soon after weaning and disappear weeks later. The disappearance of SFB coincides with the time of mucosal immune activation suggesting immune mediated clearance of the organisms at that time. The SFB are found in multiple species and contribute an important role in development of mucosal immunity. The mechanism by which the bacteria interact with the immune system has not been well defined. Ileal gut loops were prepared in 4- to 5-week-old pigs and samples were prepared for transmission electron microscopy and scanning electron microscopy. Scanning electron micrographs showed SFB distributed over the epithelial tissue of the ileum. Transmission electron micrographs showed the SFB attached to and indented into the apical cell membrane. In the attachment interface, the proximal bacterial segment possessed a small protuberance at its base. In addition, SFB were seen extended from an M cell into intimate association with an intraepithelial mononuclear cell. In this section, the SFB did not penetrate the mononuclear cell membrane. In conclusion, we provide morphological evidence of direct interaction between SFB and intraepithelial mononuclear cells.