Listeria `tricks` intestinal cells to cause sickness

Washington: A new study has found that pathogenic listeria tricks intestinal cells into helping it pass through those cells to make people ill, and, if that doesn``t work, the bacteria simply goes around the cells.

Arun Bhunia of the University or Purdue and Kristin Burkholder of the University of Michigan Medical School, found that listeria, even in low doses, somehow triggers intestinal cells to express a new protein, heat shock protein 60, that acts as a receptor for listeria.

This may allow the bacteria to enter the cells in the intestinal wall and exit into a person``s bloodstream.

"It``s possible that host cells generate more of these proteins in order to protect themselves during a stressful event such as infection.

"Our data suggest that listeria may benefit from this by actually using those proteins as receptors to enhance infection," said Burkholder.

Listeria monocytogenes is a foodborne bacteria that can cause fever, muscle aches, nausea and diarrhea, as well as headaches, stiff neck, confusion, loss of balance and convulsions if it spreads to the nervous system.

The findings have suggested that listeria may pass between intestinal cells to sort of seep out of the intestines and into the bloodstream to cause infection.

Measurable increases of the heat shock 60 protein were detected when listeria was introduced to cultured intestinal cells.

Bhunia and Burkholder also introduced listeria to intestinal cells in the upper half of a dual-chamber container and counted the number of bacteria that passed through the cells and appeared in the lower chamber.

The bacteria moved to the lower chamber faster than it is known to do when moving through cells, and did so even when a mutant form of the bacteria that do not invade the intestinal cells was used. This suggests the bacteria are moving around the cells, Bhunia said.

"The infective dose is very low. Even 100 to 1,000 listeria cells can cause infection. We believe that these mechanisms are what allow listeria to cause infections at such low levels," said Bhunia.

The findings were published in the journal Infection and Immunity.