Marine Compound Shows Promise Against Deadly Brain-eating Amoeba

WHO:

Gizmodo - Researchers at the University of California, San Diego (UC San Diego) identified rutamycin B, a compound isolated from marine bacteria, as a potential treatment against *Naegleria fowleri*.

Gizmodo - Study author Anjan Debnath is co-director of UC San Diego’s Center for Discovery and Innovation in Parasitic Diseases.

Gizmodo - Study co-author William Fenical is a distinguished professor emeritus at UC San Diego’s Scripps Institution of Oceanography.

Phys.org - Primary amoebic meningoencephalitis (PAM) is caused by the free-living amoeba *Naegleria fowleri*.

WHAT:

Gizmodo - In laboratory tests, rutamycin B killed five tested strains of *N. fowleri* within hours, including at low doses, while mostly sparing human cells.

Gizmodo - Rutamycin B reached full strength in about four hours, roughly one-quarter of the time required by amphotericin B, the primary PAM treatment.

Gizmodo - At low doses, rutamycin B was 200 to 300 times more toxic to the amoeba than to human cells.

Gizmodo - Combining rutamycin B with amphotericin B required 3% to 10% as much of the compound to work as effectively as rutamycin B alone.

Gizmodo - About 150 PAM cases have ever been reported in the United States; more than 97% of diagnosed patients die, often within days, even with treatment.

Phys.org - PAM causes rapid deterioration of brain tissue and has a fatality rate exceeding 97%; patients may have only a few days to respond to treatment.

Gizmodo - Researchers said further studies, including animal testing, are needed before rutamycin B can be tested in humans.

WHERE:

Gizmodo - *N. fowleri* lives in soil and warm freshwater and has been found in natural hot-water springs at national parks.

Gizmodo - The distribution of U.S. cases has gradually moved north, while global cases have increased.

WHEN:

Gizmodo - In laboratory tests, rutamycin B took about four hours to reach full strength.

Phys.org - PAM can progress so rapidly that patients may have only a few days to respond to treatment.

WHY:

Gizmodo - PAM occurs when *N. fowleri* enters the body through the nose, migrates to the brain, and damages brain cells while causing severe inflammation.

Gizmodo - Existing treatments can take longer to reach full potency or require doses toxic to humans and the amoeba, limiting their effectiveness.

HOW:

Gizmodo - Rutamycin B inhibits an enzyme vital to the amoeba’s energy production.

Gizmodo - The researchers said it remains unknown how effectively rutamycin B crosses the blood-brain barrier.

(UPDATED October 27, 2026 22:13 UTC)

Researchers at UC San Diego have identified rutamycin B, a compound from marine bacteria, as a promising potential treatment for primary amoebic meningoencephalitis, a usually fatal brain infection caused by the amoeba *Naegleria fowleri*. In laboratory tests, it killed five strains of the amoeba within hours while largely sparing human cells, and combining it with amphotericin B reduced the amount of rutamycin B needed for an effective result. The findings are preliminary: researchers still need to test the compound in animals and determine whether it can cross the blood-brain barrier before considering trials in people.