A decades-old drug for urinary tract infections may also work for “brain-eating” amoeba infections, which kill the vast majority of people who contract them, Science magazine reported (opens in new tab) .

The drug’s promise was demonstrated in a recent case report, published in January in the journal Emerging Infectious Diseases (opens in new tab) , which describes a 54-year-old man whose brain was infiltrated by the amoeba Balamuthia mandrillaris. The single-celled organism lives in dust, soil and water, and can enter the body through skin wounds and cuts or through the lungs, when it’s inhaled, according to the Centers for Disease Control and Prevention (opens in new tab) (CDC). The amoeba can then infiltrate the bloodstream and travel to the brain, triggering a very rare infection called “granulomatous amebic encephalitis” that kills around 90% of people affected. 

“The disease might appear mild at first but can become more severe over weeks to several months,” the CDC notes.

The man in the case report initially received treatment at a Northern California hospital for an unexplained seizure. Magnetic resonance imaging (MRI) revealed a mass on the left side of his brain, surrounded by swelling. At this point, the man was transferred to the University of California San Francisco (UCSF) Medical Center, where doctors took samples of the patient’s brain tissue and the clear fluid surrounding the brain and spinal cord. This analysis revealed B. mandrillaris in the man’s brain.  

Related: Boy dies from rare ‘brain-eating’ amoeba found in splash pad at Texas park 

After consulting the CDC, the patient’s doctors prescribed an aggressive regimen of antiparasitic, antibacterial and antifungal drugs. “It’s what’s recommended because it was what happened to be used in patients who survived,” Dr. Natasha Spottiswoode (opens in new tab) , an infectious disease physician-scientist at UCSF and first author of the case report, told Science. Unfortunately, the treatment triggered severe side effects, including kidney failure, and the patient wasn’t yet amoeba-free. RELATED STORIES—5 key facts about brain-eating amoeba

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In search of another solution, Spottiswoode dug up a 2018 report, published in the journal mBio (opens in new tab) , in which UCSF scientists found evidence that an antibiotic called nitroxoline can kill B. mandrillaris in laboratory settings. The drug is approved in Europe, but not the U.S., so the medical team sought permission from the Food and Drug Administration to use it; they received approval, started the patient on nitroxoline and observed rapid improvement, within a week.

The patient was soon discharged from the hospital and he continued to take nitroxoline at home, along with other medications; his clinicians plan to eventually discontinue his use of the drugs. In the meantime, UCSF doctors are overseeing the case of a second B. mandrillaris-infected patient who’s started receiving nitroxoline. They are seeing similar improvements, Science reported. 

Read more in Science (opens in new tab) .