Plague Bacilli Hide Out in Amoebae

Yersinia pestis, the bacterium that causes bubonic plague, can survive within the ubiquitous soil protozoan, the amoeba, by producing proteins that protect against the latter microbe's digestion. The research was published online on April 28, 2017 in Applied and Environmental Microbiology, a journal of the American Society for Microbiology. The article is titled “Yersinia pestis Resists Predation by Acanthamoeba castellanii and Exhibits Prolonged Intracellular Survival.” The research is important because plague is a re-emerging disease, according to the Centers for Disease Control and Prevention (CDC), with 95 percent of cases occurring in sub-Saharan Africa and Madagascar. Modern antibiotics are effective, but without prompt treatment, plague can cause serious illness, or death. Y. pestis spreads from rodent to rodent, and sometimes to human, often via fleas. It uses the protective niche of the amoeba to abide in when conditions are unfavorable to its spread, that is, when rodents are scarce, said Viveka Vadyvaloo, PhD, Assistant Professor, Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington. Amoebae are similar to certain human immune cells, the macrophages, in their ability to engulf bacteria, or other nourishing items of similar size. These are taken up within special compartments called vacuoles, which in both amoebae and humans are capable of digestion. "With this in mind, graduate student Javier Benavides-Montaño separately cultured three distinct Y. pestis strains that have been associated with human epidemics, with a common laboratory strain of the free-living soil amoeba, Acanthamoeba castellanii, in a medium that supports the latter's growth," said Dr. Vadyvaloo. Benavides-Montaño then tested Y. pestis' ability to enter and survive within the amoeba.
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