Adherence factors in microbes is to attach to a host cell or to an extracellular matrix. So what is the difference and similarities between fimbriae and adhesins?
Fimbrae is a catch all term to denote the hairlike projections on many gram-negative and some gram-positive bacteria, but exludes flagella. Adhesins are a subtype of fimbrae that serve as organs of attachment to cells or mucosal surfaces. Another type of fimbrae are pili, functioning in conjugation, the transfer of DNA from one bacterial cell to another (Koneman, I can't even find the year on this crazy book. Used to be the bible of determinitive bacteriology. So many hours.)