Morphological studies on fimbriae expressed by Vibrio cholerae 01

Colonization of the small intestine is an essential step in the pathogenesis of Vibrio cholerae diarrhea. At least one type of fimbriae, known as TcpA are required for the colonization process. This paper reports electron microscopic evidence that V. cholerae strains can express at least two other fimbrial types. Classical strains express three types: TcpA fimbriae are 5-6 nm in diameter and form bundles of parallel undulating filaments up to 15 micron long; Type B are 3 nm wide and of wavy morphology, and Type C are rigid, isolated filaments 5-6 nm wide and 180-800 nm long. El Tor strains express fimbriae resembling Types B and C. Types B and C were also found on a tcpA- isogenic mutant of V. cholerae 395 N1, and are thus encoded by genetically distinct loci. TcpA fimbriae, but not Types B or C, were labeled with gold-conjugated anti-TcpA antibody. Four El Tor strains, including two environmental isolates that poorly colonize humans, expressed fimbriae resembling Types B and C, but did not express TcpA. Multiple types of fimbriae may represent colonization factors for surfaces present in the environment and in the human gut. Characterization of the role of fimbriae in immunogen presentation and immunity could facilitate the improvement of cholera vaccines.