Urinary tract infections (UTIs) are very common, and it has been estimated that 60% of women experience UTI at least once at some stage of life. UTI is a major public health concern because of its high prevalence. It is more common in females compared males because shorter urethras in women allow bacteria to ascend into the bladder. Nearly half of the women population experience at least 1 episode of UTI in their lifetime, with 20-40% of them exhibiting recurrent episodes.
UTIs are caused by Gram negative bacteria Escherichia coli (E. coli) account for most cases. Initial stage of an infection is the colonization of the periurethral tissues, subsequently the passing of bacteria through the urethra. The next step involves the adherence of bacteria to the urethra and bladder walls and proliferation.
The American cranberry (Vaccinium macrocarpon) was traditionally used by North American Indians to treat Urinary tract infections. The anthocyanidins and proanthocyanidins (PAC) are tannins found in vaccinium berries acts as a natural plant defence system against microbes.
One important property of E. coli is its adherence to the host tissue. This adherence Increases the risk of Recurrence. The main protein structure involved in this mechanism is the adhesin protein, and its name is based on its shape: pili or fimbriae.
Bacterial adhesion is achieved by the binding of lectins on the cell surfaces of these fimbriae to the host tissues. Pili are small filaments that facilitate bacteria to adhere to the host tissue. These proteins can be either mannose-resistant or mannose-sensitive. The mannose- sensitive pili, called type 1 pili, allow bacterial adhesion to the urothelium. These proteins are inhibited by fructose which are present in the cranberries. The virulent strains of E. coli, drawn from patients with pyelonephritis and recurrent UTIs, have p types of fimbriae, (pyelonephritis fimbriae). These fimbriae bind to glycosphingolipids of the lipid double membrane of renal cells, which leads to renal parenchymal invasion. Cranberries function primarily by preventing the adhesion of type 1 and p-fimbriae strains (particularly from E. coli) to the urothelium. Without adhesion, the Microbes cannot infect the mucosal surface. Anti-adhesion properties are mediated by two components of cranberries: fructose, which inhibits the adherence of type 1 fimbriae, and PAC, which inhibits the adherence of p-fimbriae, thereby by prevents the risk of recurrence.
One more mechanism by which the cranberry work is the in vitro reduction in the expression of p-fimbriae in E. coli by changing the conformation of surface molecules. cranberries can decrease the virulence of E. coli strains and reduce the reduction in adherence activity even in strains with no expression of type 1 fimbriae or p-fimbriae, which adhere via an adhesin, suggesting that cranberry extracts affect a variety of fimbriae. cranberry juice can induce conformational changes in the surface macromolecules of p-fimbriated E. coli by specifically reducing fimbrial length and density. PAC could be active in the colon and the urinary tract. They can bind to uropathogenic rectal E. coli isolates, thereby rendering them anti-adherent prior to their possible introduction into the urinary tract. Most studies have focused on uropathogenic E. coli type 1 and p-fimbriated E. coli, but there are many studies which reported an inhibition of adherence for Proteus spp., P.aeruginosa, E. faecalis, S. aureus, S. typhimurium and K. pneumoniae. Even multi-drug resistant strains of E. coli exhibited inhibition of adherence to uroepithelial cells in the presence of proanthocyanidin of cranberries. The safety of cranberries has been tested, and no biochemical or haematological modifications were reported. cranberry juice could decrease E. coli adhesion up to 8 hours after consumption. To conclude UTI very common. Recurrent urinary tract infections remain challenging to treat. The main treatment option is long-term antibiotic prophylaxis. however, this poses a risk for the emergence of bacterial resistance. Some options to avoid this risk are available, using products that contains cranberry extracts can be more beneficial especially in case of Recurrent UTI.
Reference
- Hisano M, Bruschini H, Nicodemo AC, Srougi M. Cranberries and lower urinary tract infection prevention. Clinics (Sao Paulo). 2012;67(6):661-8.
