Amebic meningoencephalitides and keratitis: challenges in diagnosis and treatment

Abstract

Purpose of review: Acanthamoeba spp., Balamuthia mandrillaris, and Naegleria fowleri, although free-living amebae, also cause devastating diseases in humans leading to death. Acanthamoeba spp. and B. mandrillaris cause granulomatous amebic encephalitis, cutaneous and nasopharyngeal as well as disseminated infection. Acanthamoeba also causes a vision-threatening infection of the cornea, Acanthamoeba keratitis, principally in contact lens wearers. N. fowleri causes an acute, fulminating infection of the central nervous system, primary amebic meningoencephalitis, in healthy children and young adults who indulge in aquatic activities in fresh water. This review focuses on the recent developments in the diagnosis and treatment and clinical management of the diseases caused by these amebae.

Recent findings: Development of a multiplex real-time PCR test has made it possible to simultaneously detect all the three free-living amebae in a sample. It is a rapid assay with a short turn-around time of just 4-5 h. An early diagnosis would be helpful in initiating potentially effective treatment. A recent study reported exciting results indicating that loading of rokitamycin in chitosan microspheres improves and prolongs the in-vitro anti-Acanthamoeba activity of the drug.

Summary: Diagnoses of these infections are challenging and antimicrobial therapy is empirical, which often results in fatalities. Further research is needed to explore the possibility of a better drug delivery system that crosses the blood-brain barrier and effectively reach the central nervous system.