A recent study has determined how Salmonella is able to counter the defense mechanisms of human cells.
Researchers at Imperial College London showed that Salmonella, which can cause gastroenteritis and typhoid fever, is capable of depleting human cells of the toxic enzyme packets that they use to target invaders.
The enzyme packets, called lysosomes, constantly need to be replenished from where they are originally produced in the cells. Enzymes are carried from these "factories" to the lysozomes by means of a dedicated transport pathway and specific carrier molecules.
The study, which appears in the journal Science, showed that Salmonella can interfere with the system that moves the enzymes and restocks the lysozomes. The researchers found that Salmonella is capable of injecting a protein that prevents the cell from recycling the carrier molecules. This happens after the human cell has engulfed the bacteria, but before it can be eliminated.
Salmonella, as a result, is capable of effectively neutralizing the primary defense against it. The enzymes are rerouted out of the cell and the lysozomes effectively lose their potency.
"This seems to be a very effective way for these harmful bacteria to interfere with our cell's defence mechanisms, and then exploit the defective lysosomes to their own benefit," author David Holden said. "Our challenge now is to understand in greater detail how the injected Salmonella protein works at the molecular level, and - potentially - to exploit our findings to develop more effective vaccines. This is especially important since many Salmonella strains are now resistant to antibiotics."