Road to Bubonic Plague Less Congested Than Thought

Scientists find just a few microbes are needed to infect lymph node, cause disease A long-held theory about how bubonic plague is caused has been flipped on its head, according to scientists. Researchers from the UNC School of Medicine found that instead of using host cells, some of the plague-causing bacteria travel to lymph nodes in small numbers. The thinking was that bacteria that cause bubonic plague commandeer host cells at the site of a fleabite and are then transported to the lymph nodes—where the bacteria proliferate and cause acute disease. The researchers say the lion’s share of Yersinia pestis (plague-causing bacteria) get waylaid in a traffic jam in the skin, while heading to the lymph node, or, in the node itself. It just takes a scant few microbes, ditching the pack, to infect the lymph node and spur disease. “Anytime you find something where the host is winning, you want to exploit it,” says Virginia Miller, PhD, professor of microbiology and immunology and senior author of the paper in PLoS Pathogens. “If we can understand how the host and the bacteria contribute to this bottleneck, then this could become something we’d target so we could either ramp up what’s causing the bottleneck or slow down the infection.” The findings give us insight into ways lethal insect-borne diseases trigger infection. Y. pestis causes three types of plague—bubonic (caught from a fleabite), pneumonic (caught from breathing in the bacteria), and septicemic (a serious infection of blood). The article, titled “Dissemination of a Highly Virulent Pathogen: Tracking The Early Events That Define Infection,” in PLOS Pathogens, is found here: bit.ly/1BtaeOe Image: A single bacterium of Yersinia pestis (red) -- the pathogen that causes the plague -- made its way from the site of a fleabite to the lymph node of a mouse without the help of a host cell. (Image courtesy of the Miller lab)