Bacterial adhesins are cell-surface components or appendages of bacteria that facilitate adhesion or adherence to other cells or to surfaces, usually in the host they are infecting or living in.

In the crudest sense, bacterial adhesins serve as anchors allowing bacteria to overcome these environmental shear forces, thus remaining in their desired environment.

This prevalence marks them as key microbial virulence factors in addition to a bacterium's ability to produce toxins and resist the immune defenses of the host.

[5] This basic structure is conserved across type 1 fimbrial adhesins though recent studies have shown that in vitro induced mutations can lead to the addition of C-terminal domain specificity resulting in a bacterial adhesion with dual bending sites and related binding phenotypes.

[3] Numerous studies have shown that inhibiting a single adhesin in this coordinated effort can often be enough to make a pathogenic bacterium non-virulent.

[7] Additionally, adhesins are attractive vaccine candidates because they are often essential to infection and are surface-located, making them readily accessible to antibodies.

The effectiveness of anti-adhesin antibodies is illustrated by studies with FimH, the adhesin of uropathogenic Escherichia coli (UPEC).

[3] Recent studies from Worcester Polytechnic Institute show that the consumption of cranberry juice may inhibit the action of UPEC adhesins.

Further, an individual bacterium can produce multiple different types of adhesin, at different times, in different places, and in response to different environmental triggers.

In animal models, passive immunization with anti FimH-antibodies and vaccination with the protein significantly reduced colonization by UPEC.

[12] Multivalent adhesion molecules (MAMs) are a widespread family of adhesins found in Gram negative bacteria, including E. coli, Vibrio, Yersinia, and Pseudomonas aeruginosa.

[15] MAMs contain tandem repeats of mammalian cell entry (MCE) domains which specifically bind to extracellular matrix proteins and anionic lipids on host tissues.

Since they are abundant in many pathogens of clinical importance, multivalent adhesion molecules are a potential target for prophylactic or therapeutic anti-infectives.

The use of a MAM targeting adhesion inhibitor was shown to significantly decrease the colonization of burn wounds by multidrug resistant Pseudomonas aeruginosa in rats.

Additionally, recent studies out of Stockholm have shown that Neisseria can hitchhike on PMNs using their adhesin pili thus hiding them from neutrophil phagocytic activity.

FimH in E. coli overcomes the antibody based immune response by natural conversion from the high to the low affinity state.