Center for Tropical and Emerging Global Diseases
University of Georgia
A Nexstar Media wire story on Naegleria fowleri (aka “brain-eating” amoeba) featuring CTEGD director Dennis Kyle has been picked up by news outlets.
Brain-eating amoeba: How do most infections occur? (NewsNation)
Brain-eating amoeba: How do infections occur, and where are they most common? (The Hill)
Cassie Russell, a graduate student in the Department of Infectious Diseases, was an undergraduate when she first heard of Naegleria fowleri, also known as the brain-eating amoeba. While whole lectures in her parasitology course had been dedicated to other parasites, N. fowleri was barely a mention.
“I remember maybe 15 minutes was spent on it,” said Russell. “I was shocked that was all that was known about this deadly organism.”
N. fowleri causes the acute neurological disease primary amoebic meningoencephalitis (PAM). There have been hundreds of reported cases of PAM, but only seven survivors worldwide, according to the Centers for Disease Control and Prevention.
“I had the opportunity to speak with families in Florida who had lost someone to Naegleria fowleri infection,” she said. “The fear they had in not knowing what was wrong with their loved one and then learning that there was very little that could be done—their stories were just heartbreaking.”After arriving at UGA, Russell was pleased to find out that N. fowleri was one of the parasites being studied in Dennis Kyle’s laboratory at the Center for Tropical and Emerging Global Diseases.
Individuals, most commonly young children, become infected when they inhale warm freshwater contaminated with N. fowleri. This typically occurs during the late summer months when people are participating in recreational activities in rivers and lakes, but it can also occur when people use unsterilized tap water in nasal irrigation devices. It is more likely to occur in the southern United States, but infection is very rare. Between 2011 and 2020 only 33 cases were reported in the United States, according the CDC.
N. fowleri is one of the most neglected of the neglected tropical diseases. However, knowledge about the parasite has been growing since the 1960s as scientists build on new data and apply new technology. Russell is doing her part and was the lead on a study recently published in Microbiology Spectrum where, for the first time, drug susceptibility was tested across 11 clinical isolates.
“Current drug treatment is a cocktail of six different drugs,” said Russell. “However, only a few isolates have been tested in the lab for susceptibility. We don’t know if some drugs work better for different strains.”
A big question facing researchers is why these drugs show effectiveness in the lab when so few real-world cases have been successfully treated. Russell suspected that other factors were at play in treatment failure, such as genetic differences among geographically distinct amoeba populations.
The 11 isolates used in the study came from patients who contracted N. fowleri in different geographic regions. Russell found that these isolates had significant differences in susceptibility to seven of the eight drugs currently used to treat the infection.
The need for effective and fast-acting treatments is especially great. PAM is almost always fatal, with death occurring about a week after the initial onset of symptoms.
Doctors are racing against the clock as there is often a delay in diagnosis: The symptoms mimic meningitis, and N. fowleri is a rare infection. The drugs used can also be pretty toxic, so identifying the safest and most effective drug treatment could significantly improve outcomes.
Russell’s findings are another stepping stone to propel N. fowleri research toward increased understanding of this parasite and ultimately better treatments. For example, she realized that there is not a gold standard for genotyping.
“Researchers could be talking about genetically different isolates but not realize it,” said Russell.
In addition to creating a genotyping standard, she has identified combinational drug studies to test for synergism as a next step. For now, though, Russell is focusing on another need in the fight against N. fowleri—diagnostics.
“Awareness, improved diagnostic techniques and faster-acting drugs are needed to improve outcomes,” she said.
Naegleria fowleri is a pathogenic free-living amoeba that is commonly found in warm freshwater and can cause a rapidly fulminant disease known as primary amoebic meningoencephalitis (PAM). New drugs are urgently needed to treat PAM, as the fatality rate is >97%. Until recently, few advances have been made in the discovery of new drugs for N. fowleri, and one drawback is the lack of validated tools and methods to enhance drug discovery and diagnostics research. In this study, we aimed to validate alternative methods to assess cell proliferation that are commonly used for other cell types and develop a novel drug screening assay to evaluate drug efficacy on N. fowleri replication. EdU (5-ethynyl-2′-deoxyuridine) is a pyrimidine analog of thymidine that can be used as a quantitative endpoint for cell proliferation. EdU incorporation is detected via a copper catalyzed click reaction with an Alexa Fluor-linked azide. EdU incorporation in replicating N. fowleri was validated using fluorescence microscopy, and quantitative methods for assessing EdU incorporation were developed by using an imaging flow cytometer. Currently used PAM therapeutics inhibited N. fowleri replication and EdU incorporation in vitro. EdA (7-deaza-2′-deoxy-7-ethynyladenosine), an adenine analog, also was incorporated by N. fowleri but was more cytotoxic than EdU. In summary, EdU incorporation could be used as a complimentary method for drug discovery for these neglected pathogens.
Emma V Troth, Dennis E Kyle. Antimicrob Agents Chemother. 2021 Jun 17;65(7):e0001721. doi: 10.1128/AAC.00017-21.
Dr. Dennis Kyle, director of CTEGD and professor in the departments of cellular biology and infectious diseases, is the featured guest on Episode 5 of the People, Parasites & Plagues Podcast. He talks about a deadly disease caused by Naegleria fowleri, also known as the brain-eating amoeba.
The podcast is also available at Amazon, iTunes, Google, Spotify, Stitcher, Audible, and TuneIn
People, Parasites & Plagues is a podcast aimed at delivering information about the fascinating pathogens among us from the impressive professionals who study them.
Join hosts Dr. David Peterson and Dr. Liliana Salvador, two infectious disease researchers from the University of Georgia, as they explore the past, present, and future of science.
Tune in every other week for a new and enlightening episode as they unpack the details surrounding some of Earth’s most perplexing diseases. Look for the People, Parasites & Plagues Podcast on your favorite Podcast service!
Naegleria fowleri is a pathogenic free-living amoeba that is commonly found in warm, freshwater and can cause a rapidly fulminant disease known as primary amoebic meningoencephalitis (PAM). New drugs are urgently needed to treat PAM, as the fatality rate is >97%. Until recently, few advances have been made in the discovery of new drugs for N. fowleri and one drawback is the lack of validated tools and methods to enhance drug discovery and diagnostics research. In this study we aimed to validate alternative methods to assess cell proliferation that are commonly used for other cell types and develop a novel drug screening assay to evaluate drug efficacy on N. fowleri replication. EdU (5-ethynyl-2′-deoxyuridine) is a pyrimidine analog of thymidine that can be used as a quantitative endpoint for cell proliferation. EdU incorporation is detected via a copper catalyzed click reaction with an Alexa Fluor linked azide. EdU incorporation in replicating N. fowleri was validated using fluorescence microscopy and quantitative methods for assessing EdU incorporation were developed by using an imaging flow cytometer. Currently used PAM therapeutics inhibited N. fowleri replication and EdU incorporation in vitro EdA (5’ethynyl-2′-deoxyadenosine), an adenine analog, also was incorporated by N. fowleri, but was more cytotoxic than EdU. In summary, EdU incorporation could be used as a complimentary method for drug discovery for these neglected pathogens.
Naegleria fowleri is a pathogenic, thermophilic, free-living amoeba which causes primary amebic meningoencephalitis (PAM). Penetrating the olfactory mucosa, the brain-eating amoeba travels along the olfactory nerves, burrowing through the cribriform plate to its destination: the brain’s frontal lobes. The amoeba thrives in warm, freshwater environments, with peak infection rates in the summer months and has a mortality rate of approximately 97%. A major contributor to the pathogen’s high mortality is the lack of sensitivity of N. fowleri to current drug therapies, even in the face of combination-drug therapy. To enable rational drug discovery and design efforts we have pursued protein production and crystallography-based structure determination efforts for likely drug targets from N. fowleri. The genes were selected if they had homology to drug targets listed in Drug Bank or were nominated by primary investigators engaged in N. fowleri research. In 2017, 178 N. fowleri protein targets were queued to the Seattle Structural Genomics Center of Infectious Disease (SSGCID) pipeline, and to date 89 soluble recombinant proteins and 19 unique target structures have been produced. Many of the new protein structures are potential drug targets and contain structural differences compared to their human homologs, which could allow for the development of pathogen-specific inhibitors. Five of the structures were analyzed in more detail, and four of five show promise that selective inhibitors of the active site could be found. The 19 solved crystal structures build a foundation for future work in combating this devastating disease by encouraging further investigation to stimulate drug discovery for this neglected pathogen.
Logan Tillery, Kayleigh Barrett, Jenna Goldstein, Jared W Lassner, Bram Osterhout, Nathan L Tran, Lily Xu, Ryan M Young, Justin Craig, Ian Chun, David M Dranow, Jan Abendroth, Silvia L Delker, Douglas R Davies, Stephen J Mayclin, Brandy Calhoun, Madison J Bolejack, Bart Staker, Sandhya Subramanian, Isabelle Phan, Donald D Lorimer, Peter J Myler, Thomas E Edwards, Dennis E Kyle, Christopher A Rice, James C Morris, James W Leahy, Roman Manetsch, Lynn K Barrett, Craig L Smith, Wesley C Van Voorhis (2021) Naegleria fowleri: Protein structures to facilitate drug discovery for the deadly, pathogenic free-living amoeba. PLoS ONE 16(3): e0241738. https://doi.org/10.1371/journal.pone.0241738
Dennis Kyle, director of the Center for Tropical and Emerging Global Diseases, was interviewed during the 4th Annual Amoeba Summit about his work with Naegleria fowleri. Listen to the interview at Outbreak News Today.
Beatrice Colon, an Illinois native, is a Ph.D. trainee in Dennis Kyle’s laboratory. She holds a Bachelor of Science degree from the University of Illinois at Urbana-Champaign and a Master of Science degree from the University of South Florida (USF). She began her Ph.D. at USF as well.
Beatrice moved to the University of Georgia in January 2017 with the Kyle Lab.
“I decided to transfer universities because of the excellent infectious disease department,” said Beatrice.
“My favorite thing about the CTEGD is the openness for collaborations; the center is also very focused on training a new generation of scientists. “
Beatrice is currently working on a drug discovery project for the brain-eating amoeba, Naegleria fowleri. The disease was the major factor that drew her to the project. Primary amoebic meningoencephalitis is nearly always fatal and affects young healthy children. Moreover, there is not an effective drug treatment for people that do get infected with the amoeba.
In her short time at UGA, Beatrice has won first place for a poster presentation at the graduate student and postdoc symposium. She was also selected for the Biology of Parasitism course at Woods Hole, MA this past summer.
“This course was definitely a career-changing experience – I was able to work with a variety of infectious diseases and learn techniques that were not available for the parasite I work on.”
Beatrice is interested in staying in drug discovery for infectious diseases and currently looking at positions in both academia and industry.
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