Proanthocyanidins (PAC) in the juice of the American cranberry inhibit uropathogenic P. fimbriae of E. coli and other bacteria so the bacteria does not adhere to the urinary tract wall.*  (specifically Type-A PAC found only in the vaccinium macrocarpon species of cranberry)

With the minimum dose of 36 mg PAC and an anti-adhesion activity (AAA) of <.50 (mg/mL), the PAC will bind to P. fimbriae of the uropathogenic bacteria to prevent attachment to the uroepithelial cell wall. The bacteria are effectively neutralized and are then washed out with the urine stream. *NEJM Volume 339:1085-1086 October 8, 1998 Number 15

MECHANISM OF ACTION
PAC RESULTS IN ANTI-ADHESION 

 

*Amy B. Howell, Henry Botto et al. BMC Infectious Diseases 2010, 10:94.