Amoebae may play a key role in the spread of deadly plague bacteria

A study published in the journal Emerging Infectious Diseases revealed that the deadly plague bacteria Yersinia pestis (Y. pestis), a pathogen infamously associated with the spread of the Black Death epidemic in the 14th century, was either resistant or transiently resistant to certain species of amoeba. The researchers also found that the bacteria may even use the amoeba species as a host and reservoir for its future reemergence.

• A team of researchers at the Colorado State University collected soil samples from 24 prairie dog burrows from eight prairie dog colonies in the Pawnee National Grassland of northeastern Colorado to assess the co-occurrence of amoeba and Y. pestis.
• The scientists then isolated five amoeba species — including A. castellanii, A. lenticulata, A. polyphaga, D.discoideum, and V. vermiformis — by using modified culture methods, while Y. pestis strains were cultured from frozen stocks in lysogeny broth (LB) medium.
• The experts also carried out intraameba bacterial survival and replication assays in order to determine the survival of Y. pestis strains in five amoeba species following phagocytic activities.
• The researchers found that while Y. pestis was known to reside in the digestive and central vacuoles of certain amoeba species, it did not survive beyond 24 hours postinfection in four amoeba strains including A. castellanii, A. lenticulata, A. polyphaga and V. vermiformis .
• However, the scientists observed that Y. pestis was able to survive the D.discoideum strain for more than 48 hours postinfection under variable treatment conditions.
• The scientists also found that the plague bacteria had significantly higher survival and recoverability rate when co-cultured with amoeba compared with monocultured controls.

The research team noted that the results may shed light on how plague outbreaks may spread, stay dormant and eventually reemerge. The scientists also expressed hope that the findings would eventually help prevent human cases of plague by effectively determining how the deadly pathogen persists.

Journal reference:

David W. Markman, Michael F. Antolin, Richard A. Bowen, William H. Wheat, Michael Woods, Mercedes Gonzalez-Juarrero, Mary Jackson. YERSINIA PESTIS SURVIVAL AND REPLICATION IN POTENTIAL AMEBA RESERVOIR. Emerging Infectious Diseases, 2018; 24 (2): 294 DOI: 10.3201/eid2402.171065