MODELING BIOFILM-ASSOCIATED URINARY-TRACT INFECTIONS IN ANIMALS

Chronic infections in the urinary environment include medical device related infections, chronic cystitis, chronic prostatitis, and infected struvite stones. Many different uropathogens are associated with these infections, but their common feature is adhesion, followed by growth as microcolonies and biofilms. In acute infections, the disease runs its course before being cleared by antibiotics or host defence mechanisms present at the tissue surface (e.g the mucous layer and the immune response) and within the urine itself (e.g. low iron levels and high osmolality due to urea) and micturition. Chronic urinary tract infections (UTI) arise when the natural host defences are defective or obstructed by the presence of a foreign object such as a catheter or calculus. In these cases, adherent pathogens are not cleared or eradicated. Rather they coat themselves with an extracellular polysaccharide matrix, and upon growth form encapsulated microcolonies and biofilms. This mode of growth enables the biofilm to be notoriously resistant to both the immune response of the host and to antibiotics. In order to accurately mimic these chronic human UTIs in animals, it is essential that the uropathogens are encouraged to grow in their natural state as biofilms. In this report, several models used to examine chronic biofilm-associated infections are described.