Fimbria

A fimbria (plural fimbriae), also referred to as "attachment pili" by some scientists, is an appendage composed of curlin proteins that can be found on many Gram-negative and some Gram-positive bacteria that is thinner and shorter than a flagellum. Bacteria can grow these if they have the gene for it and are in the proper environment for it. Like capsules, they grow significantly better in live hosts than in lab media. Fimbriae allow bacteria to adhere to soft tissue, and is a trait that is used to determine virulence in bacteria
E. coli have fimbriae that attach to the human gastrointestinal tract.
Neisseria gonorrheae uses fimbriae to attach to the eyes of a newborn child during childbirth and infect the newborns with neonatal conjunctivitis, also known as ophthalmia neonatorum. If the Neisseria bacteria is in one's system, the bacteria is virulent and has fimbriae.