The human immune system is pretty good at wiping out dangerous invaders – which is why some of these invaders have developed ways to avoid detection until they're ready. Now, researchers from the University of Virginia (UVA) may have found a way to prevent infections by making sure that these bugs are never ready. The team has uncovered how pathogenic E. coli senses its environment to stay stealthy until it reaches the right spot to kickstart an infection.
E. coli is a common inhabitant of your gut, but most of the time it's a relatively well-behaved guest. Occasionally though, a bad burger can introduce more unruly strains that can cause cramps, diarrhea, vomiting, and other common symptoms of food poisoning.
But now, two researchers from the UVA School of Medicine, Melissa Kendall and Elizabeth Melson, say they have uncovered new details about how pathogenic E. coli establishes itself in the body. The team found that the bug senses its surroundings as it moves through the body, biding its time until it gets to the large intestine.
"Bacterial pathogens typically colonize a specific tissue in the host," says Kendall. "Therefore, as part of their infection strategies, bacterial pathogens precisely time deployment of proteins and toxins to these specific colonization niches in the human host. This allows the pathogens to save energy and avoid detection by our immune systems and ultimately cause disease."
The researchers found that E. coli uses oxygen levels as its cue to take hold. It uses a small RNA fragment called DicF to sense levels of the gas around it. Once those levels are low enough – indicating it's reached the low-oxygen environment of the large intestine – DicF activates genes to let the bacteria know to start infecting cells. Once settled it begins producing Shiga toxins, which are responsible for many of those unpleasant symptoms.
The team says that other bacteria, like Shigella and Salmonella, might use similar systems to cause infections. Further research will need to be done to investigate that, however.
Armed with this new information, scientists could start studying how to mess with this sensing system, which could theoretically prevent infections. The strategy might even turn out to be a viable alternative to antibiotics, which bacteria are fast developing resistance to.
"By knowing how bacterial pathogens sense where they are in the body, we may one day be able to prevent E. coli, as well as other pathogens, from knowing where it is inside a human host and allow it to pass through the body without causing an infection," says Kendall. "This may be an effective strategy to limit infection, and because we are not targeting growth or survival, E. coli may not develop drug resistance – it just doesn't know where it is."
The research was published in the journal PNAS.
Source: University of Virginia
