Researchers at the University of California San Diego have isolated a marine bacterium compound called rutamycin B that kills the brain-eating amoeba Naegleria fowleri in just four hours. The discovery, detailed in a study published Monday, October 26, 2026, in Marine Drugs by authors including Hayley Fong, PhD, offers a potential alternative for a disease with a fatality rate exceeding 97 percent.
Primary amoebic meningoencephalitis is a rare and devastating infection caused by the free-living amoeba Naegleria fowleri. The organism lives in soil and warm freshwater, entering the human body through the nose before migrating to the central nervous system to destroy brain tissue. With only around 150 known cases recorded in the United States, the disease progresses so rapidly that infected individuals typically have only days to respond.
Research has additionally indicated that human visitors frequently encounter the amoeba in locations like national park thermal springs, and that the microscopic entity has slowly migrated northward across the years. When the organism is simply ingested in water, it typically feeds on bacteria and is not dangerous to humans. However, infections caused by N. fowleri are hard to treat and nearly always fatal once an infection takes hold.
According to information detailed in the journal Marine Drugs, the gold-standard treatment, amphotericin B, takes roughly 16 hours to reach full potency against the parasite.
Rutamycin B Speeds Up Potency and Protects Human Cells
Beyond its speed, researchers found the compound demonstrated high selectivity. Laboratory assays showed rutamycin B was between 200 and 300 times more lethal to the parasite than to human cells.
Combining rutamycin B with amphotericin B allowed scientists to achieve identical results using only 3 percent to 10 percent of the original standalone dose of the marine compound. Investigators suggest that the unique chemical makeup of rutamycin B renders it an encouraging prospect for upcoming drug development.
University of California San Diego Researchers Detail Ocean Library Potential
The discovery stems from efforts to screen compounds harvested from marine environments. The investigation was spearheaded by Debnath, Fenical, alongside Hayley Fong, PhD, who undertook this endeavor as part of her doctoral studies at UC San Diego. Galang and R. Iizumi. The research was funded in part by grants from the National Institutes of Health under project numbers R21EY034294 and R21AI171538. PCT/US26/18919, covering aspects of the work.
Rutamycin B Requires Animal Studies and Blood-Brain Barrier Testing
While the laboratory results show significant promise and point toward a promising new therapeutic strategy for a disease that has historically left almost no survivors, substantial hurdles remain before the compound can be evaluated in humans. There is much work to be done before this discovery can translate to medicine. The research team must still conduct studies using live animal disease models to confirm efficacy, and investigators need to determine whether rutamycin B can successfully cross the blood-brain barrier to reach infections centered in the central nervous system.
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