from Scientific American, August 25, 2016
by Knvul Sheikh
The sneaky germ uses a mechanism like that of white blood cells to reach vulnerable tissues and hide from antibiotics
Lyme disease is an incredibly evasive adversary. No one is entirely sure how the bacterium that causes it spreads so widely throughout the body or why symptoms sometimes persist after the infection has been treated with antibiotics. Now researchers at the University of Toronto may finally have an explanation: The tiny, spiral-shaped bacterium calledBorreliaburgdorferi can quickly grapple along the inner surfaces of blood vessels to get to vulnerable tissues or to hiding places where it can hole up beyond the reach of drugs.
B. burgdorferi uses a special adhesive protein on its surface to grab like a hook onto the endothelial cells that line blood vessels, attaching and detaching rapidly as it migrates to its destination, the Toronto microbiologists explain in a new study published Thursday in Cell Reports. “This mechanism is how the bacteria can overcome the fast flow of blood and avoid getting swept away,” says lead author Rhodaba Ebady. It is also likely that this tactic helps the pathogens get to sites where they are able to evade the immune system and treatment, Ebady says.
The initial infection is transmitted to humans via the bite of an infected black-legged tick (aka deer tick), which usually leaves behind a characteristic bull’s-eye rash. Symptoms can include fever, headache and fatigue. It can be treated with antibiotics if it is caught early on. But in about 20 percent of the cases severe symptoms such as joint pain and cognitive problems last even after treatment—a condition physicians call posttreatment Lyme disease. Other more chronic symptoms can be similar to those of different illnesses such as arthritis or peripheral neuropathy, and scientists disagree about whether or not they should be labeled Lyme disease.
Very few other bacteria can bring on such a variety of symptoms or infect such hard-to-reach tissues, says Kim Lewis, a professor of microbiology and director of the Antimicrobial Discovery Center at Northeastern University. “Bacteria that cause syphilis, meningitis and leptospirosis are some examples, but they have one or two target organs,” says Lewis, who was not involved in the new study. “B. burgdorferi, however, seems to be able to sneak into all of these areas, and one of the biggest unsolved problems in Lyme disease is how it gets to all of those places.”