Are amoebae safe harbors for plague?

January 16, 2018 by Anne Manning, Colorado State University
Fluorescent confocal images of amoebae after experimental co-culture with Yersinia pestis. Credit: David Markman/Colorado State University

Amoebae, single-celled organisms common in soil, water and grade-school science classrooms, may play a key role in the survival and spread of deadly plague bacteria.

New Colorado State University research shows that , Yersinia pestis, not only survive, but thrive and replicate once ingested by an amoeba. The discovery could help scientists understand why plague outbreaks can smolder, stay dormant for years, and re-emerge with a vengeance.

The study in Emerging Infectious Diseases was led by David Markman, a Vice President for Research Fellow and Department of Biology graduate student working with Professor Michael Antolin. A former government researcher for malaria vaccines, Markman is investigating whether plague bacteria use amoebae as unwitting hosts to evade detection and multiply.

The research is part of a larger effort led by Mary Jackson, professor in the Department of Microbiology, Immunology and Pathology, to investigate various infectious diseases' interactions with amoebae, including bovine tuberculosis and melioidosis. The studies have been supported by a Vice President for Research initiative called One Health.

Plague, most famous for the Black Death of the 14th century, is alive today and is experiencing a re-emergence particularly in Sub-Saharan Africa, according to the Centers for Disease Control and Prevention. In Colorado, animals including prairie dogs and black-footed ferrets carry fleas that host the bacteria. Outbreaks can wipe out whole prairie dog colonies, and humans or pets can also become infected.

Plague, unlike many other , seems to go dormant after an outbreak and re-emerge via the same strains of bacteria, indicating that the bacteria have lain quiet, rather than mutating. Where they go during this quiet period has eluded scientists. Markman's study provides new support for the theory that amoebae are the answer.

Plague hosts

Ubiquitous in soil and water, amoebae may be ideal hosts for plague bacteria when they leach into the ground from, say, a recently deceased prairie dog. To test the theory, Markman and teammates donned protective suits and took soil samples near plague outbreaks in prairie dog colonies. The researchers isolated different species of amoebae and tested whether the bacteria survived ingestion by the various amoebae.

In the lab, the plague bacteria lived for up to 48 hours inside the amoeba, and could possibly survive for longer, Markman said. A species of amoeba called Dictyostelium discoideum seemed to make the best home for plague.

"The bacteria were not just hanging out, but they were surviving and actually quite happy inside the amoebae, and replicating," Markman said. "By contrast, most bacteria get digested by amoebae and are decimated in under an hour."

Markman's hope is to help prevent human cases of plague by being able to identify how the disease persists. He's currently supported by a Department of Defense fellowship, which is aimed at identifying whether such amoeba-resistant plague could be used as bioterrorism agents.

Dormancy in cyst form

The scientists' next step is to further probe not only how long plague can survive in amoebae, but also whether -filled can develop into a resilient, cystic phase, and re-animate years later.

"If [our lab] can show that the can stay in the cysts for years, it could explain outbreaks followed by two years of dormancy and re-emergence seemingly out of nowhere," Markman said.

Explore further: Why health officials are concerned about the Madagascar plague outbreak

Related Stories

Why health officials are concerned about the Madagascar plague outbreak

November 15, 2017
A large outbreak of plague, including the rare form known as pneumonic plague, has health officials in Madagascar working to prevent the bacterial infection from spreading to neighboring countries. The World Health Organization ...

Rats may not have driven the black death plague after all

January 16, 2018
(HealthDay)—It's thought to have killed between 30 and 60 percent of Europe's population, but the Black Death plague may not have been spread by flea-infested rats, Norwegian scientists report.

Plague-riddled prairie dogs a model for infectious disease spread

January 13, 2016
Every now and then, colonies of prairie dogs are wiped out by plague, an infectious disease most often associated with the Black Death of the 14th century.

Recommended for you

'Game changer' tuberculosis drug cures 9 in 10

October 22, 2018
A new treatment for a drug-resistant strain of tuberculosis can cure more than 90 percent of sufferers, according to a trial hailed Monday as a "game changer" in the fight against the global killer.

AI doctor could boost chance of survival for sepsis patients

October 22, 2018
Scientists have created an artificial intelligence system that could help treat patients with sepsis.

Consuming caffeine from coffee reduces incident rosacea

October 22, 2018
(HealthDay)—Caffeine intake from coffee is inversely associated with the risk for incident rosacea, according to a study published online Oct. 17 in JAMA Dermatology.

Scientists in Sweden may have figured out one way acne bacteria defies treatment

October 22, 2018
Researchers in Sweden have discovered how acne-causing bacteria feed off their human hosts. The study, which was performed at KTH Royal Institute of Technology, could make it possible to find effective ways to treat severe ...

A guide to Acute flaccid myelitis (AFM), the rare, polio-like illness making young children sick

October 22, 2018
A fast-acting, polio-like illness has sickened 62 young children, with an average age of 4, in 22 U.S. states so far this fall.

Home-based biofeedback therapy is effective option for tough-to-treat constipation

October 22, 2018
Biofeedback therapy used at home is about 70 percent effective at helping patients learn how to coordinate and relax bowel muscles and relieve one of the most difficult-to-treat types of constipation, investigators report.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.