Successful Treatment of Balamuthia mandrillaris Granulomatous Amebic Encephalitis with Nitroxoline

Abstract

A patient in California, USA, with rare and usually fatal Balamuthia mandrillaris granulomatous amebic encephalitis survived after receiving treatment with a regimen that included the repurposed drug nitroxoline. Nitroxoline, which is a quinolone typically used to treat urinary tract infections, was identified in a screen for drugs with amebicidal activity against Balamuthia.

Keywords: Balamuthia mandrillaris; Infectious encephalitis; ameba; ameba drug effects; granulomatous amebic encephalitis; meningitis/encephalitis; nitroxoline; parasites.

Figure 1

Timeline of events and medications for patient with granulomatous amebic encephalitis, California, USA. Grey bar shows days since initial evaluation; diamonds indicate interval magnetic resonance images; blue diamonds indicate magnetic resonance images taken before and after administration of nitroxoline. Medications at the bottom are other treatments administered. Solid lines refer to the dosages indicated in article text, and dotted lines indicate dose reduction. LP, lumbar puncture; UCSF, University of California, San Francisco Medical Center, San Francisco, California, USA; uPCR, universal broad-range PCR amplicon sequencing.

Figure 2

Diagnostic findings for patient with granulomatous amebic encephalitis, California, USA. A) Brain biopsy sample. Granulomas are noted in a perivascular pattern. Scattered structures (arrows) with large nuclei and abundant cytoplasma are concerning for amebic trophozoite forms. Occasional structures with a large nucleus present within a relatively rigid outline (lower right image) are suspicious for amebic cysts, the dormant, thick-walled life stage. B) Magnetic resonance images obtained before and after nitroxoline treatment. Upper row shows axial gadolinium-enhanced T1-weighted images; lower row shows axial fluid-attenuated inversion recovery images. Images in the left series were obtained on day 96 after initial visit, 1 week before nitroxoline initiation; images in the right series were obtained on day 156 after initial visit, 7 weeks after nitroxoline initiation. BV, blood vessel.