The bacterium Listeria monocytogenes, which can cause listeriosis when ingested in contaminated foods, has long been studied as a model system for understanding bacterial infections, yet it still has secrets to reveal. While the bacteria are widely-distributed in the environment, there is a paradoxically low incidence of the disease, and the incubation period can be very long. Recent evidence that L. monocytogenes can cause asymptomatic infections, difficult to detect, may help explain these phenomena. During a typical Listeria infection (pictured, with the bacteria in red), the pathogens travel along the host cell’s cytoskeleton to move within and between cells. In an asymptomatic phase, the bacteria find refuge in intracellular compartments known as lysosomal vacuoles, where they escape the notice of the immune system and are less affected by antibiotics. This new understanding of the disease should change the way we approach the diagnosis and treatment of Listeria infections.
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