A recent review in Nature Microbiology details the sequence of events leading from biofiilm formation to CAUTI. A good use of graphics to aid understanding.
The production of extracellular polymeric substances by bacteria attached to the catheter allows the formation of a crystalline biofilm, which protects the community from the host immune system and from antibiotics. In addition, these structures prevent proper urine drainage, resulting in reflux and promoting the progression to pyelonephritis, septicaemia and shock. Finally, production of the bacterial toxins is important for tissue destruction and bacterial dissemination to the kidneys