Cranberry Juice and the Mechanical Forces Involved in the Attachment of E. coli O157:H7
Researchers at Worcester Polytechnic Institute (WPI) in Massachusetts may have discovered why cranberry juice fights off E. coli O157:H7 infections. In a paper published this month by Molecular Nutrition and Food Research, “Direct adhesion force measurements between E. coli and human uroepithelial cells in cranberry juice cocktail“, Professor Terri Camesano and his team present the first specific measurements of the mechanical forces involved in the attachment of the virulent E. coli to human urinary tract cells.
The study also documents how the force of attachment is reduced in the presence of cranberry juice cocktail. “This is not a clinical study—it’s a mechanical study that shows us the direct forces that can lead to infection,” Camesano said.
E. coli O157:H7 is covered with small hair-like projections known as fimbriae which act like hooks and latch onto cells that line the urinary tract. When enough of the virulent E. coli adhere to cells in this way, they cause an infection. Previous work by Camesano has shown that exposure to cranberry juice causes the fimbriae on E. coli to curl up, reducing their ability to attach to urinary tract cells.
“We know, on average, how many fimbriae are on each E. coli cell. And the total force we measured correlates with that number. So the data lead us to believe that the fimbriae each bind to a specific receptor on the uroepithelial cells,” Camesano said.
The data showed that the attachment force of the virulent E. coli weakened as the amount of cranberry juice cocktail increased. The study also showed that a strain of E. coli without fimbriae did not bind well to the human urinary tract cells, regardless of the concentration of cranberry juice cocktail, providing further evidence that fimbriae are essential for infection.
Furthermore, Camesano’s team found that in the absence of cranberry juice, the strength of the virulent E. coli’s bond to the human cells was so strong that it could not be broken by the typical force of urine flowing through a person’s urinary tract. However, as the cranberry juice concentration increased, the bond weakened to the point where the E.coli could be stripped away by the force of flowing urine. “The shear force created by flowing urine is a defense mechanism against urinary tract infection,” Camesano said.
Tags: E coli
