Honors College Thesis

Establishing Caenorhabditis elegans as a model for Mycobacterium avium subspecieshominissuis infection and intestinal colonization

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  • Mycobacterium avium subspecies hominissuis (MAH) causes potentially lethal opportunistic infections in immunocompromised individuals. Lack of a good animal model system currently hinders in vivo study of MAH virulence. Here we applied the tractable organism Caenorhabditis elegans (C. elegans), as a surrogate host to study the virulence of MAH. Worms were fed MAH and assayed for ability of MAH to infect intestinal epithelium and for the cytotoxic effects of the bacterial infection on C. elegans. It was observed that viable MAH number increases, during feeding, in the intestinal lumen in a time dependent manner. Ingestion of MAH was deemed non-toxic to worms as MAH-fed populations had similar survival curves to those C. elegans fed E. coli strain OP50. Pulse-chase analysis using E. coli strain OP50 revealed that MAH colonize the intestinal tract, and viable MAH remain within the intestine. Using histopathology and transmission electron microscopy we demonstrate that MAH localizes in the intestinal lumen, and establishes an interaction with intestinal epithelium. Bacterial colonization appears to have a detrimental effect on the microvilli of the intestinal epithelial cells. Previous studies have identified the MAH ΔGPL strain, containing a mutation in glycopeptidolipid production, as deficient in binding to human epithelial cells (HEp-2), as well as deficient in its ability to bind to and colonize the intestinal tract of C. elegans as efficiently as wild-type MAH. These data indicate the C. elegans may serve as a useful model system for studying MAH pathogenesis and in determining the mechanisms used by MAH during infection and colonization of the intestinal epithelium.
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