Here’s how brain-eating amoebas may infect people

Naegleria fowleri, known widely as the brain-eating amoeba, typically dine on bacteria in ponds. But the amoeba’s meal-seeking skills might make it uniquely suited to crawling up people’s noses and into their brains. Naegleria amoebas are intrepid explorers, probing nooks and crannies in the lab — and they’re persistent, too.

When creeping down narrow passageways, the amoebas charge relentlessly forward, almost never turning back, researchers report September 10 in the Proceedings of the National Academy of Sciences. Fritz-Laylin’s work helps flesh out a largely skeletal picture of Naegleria behavior. N. fowleri amoebas don’t routinely harm humans.

They usually dwell in warm bodies of fresh water, where they squirm through sediment and mind their own business. But on rare occasions, the creatures can be washed up a swimmer’s nose. As the amoebas migrate through the nasal cavity and into the brain, they destroy and eat tissue.

Then they begin to reproduce, usually with lethal consequences. The United States typically sees fewer than 10 Naegleria infections each year, often at summer swimming spots, but nearly every one is fatal. In the lab, Fritz-Laylin’s team tested Naegleria amoebas’ ability to move through different environments.

They focused on N. gruberi, a harmless species that shares behaviors with its brain-eating relative. The researchers placed the amoebas on glass-bottom dishes containing narrow microchannels and watched them move under a microscope. They squeezed through channels smaller than themselves and seemed to be interested in exploring.

When the amoebas encountered a channel opening, they very rarely left it, Fritz-Laylin says. Confinement sometimes sped them up, too. Inside the largest channels tested, the amoebas still zipped along twice as fast as cells on the outside.