Acanthamoebaspp. as Agents of Disease in Humans

Abstract

Acanthamoeba spp. are free-living amebae that inhabit a variety of air, soil, and water environments. However, these amebae can also act as opportunistic as well as nonopportunistic pathogens. They are the causative agents of granulomatous amebic encephalitis and amebic keratitis and have been associated with cutaneous lesions and sinusitis. Immuno compromised individuals, including AIDS patients, are particularly susceptible to infections with Acanthamoeba. The immune defense mechanisms that operate against Acanthamoeba have not been well characterized, but it has been proposed that both innate and acquired immunity play a role. The ameba's life cycle includes an active feeding trophozoite stage and a dormant cyst stage. Trophozoites feed on bacteria, yeast, and algae. However, both trophozoites and cysts can retain viable bacteria and may serve as reservoirs for bacteria with human pathogenic potential. Diagnosis of infection includes direct microscopy of wet mounts of cerebrospinal fluid or stained smears of cerebrospinal fluid sediment, light or electron microscopy of tissues, in vitro cultivation of Acanthamoeba, and histological assessment of frozen or paraffin-embedded sections of brain or cutaneous lesion biopsy material. Immunocytochemistry, chemifluorescent dye staining, PCR, and analysis of DNA sequence variation also have been employed for laboratory diagnosis. Treatment of Acanthamoeba infections has met with mixed results. However, chlorhexidine gluconate, alone or in combination with propamidene isethionate, is effective in some patients. Furthermore, effective treatment is complicated since patients may present with underlying disease and Acanthamoeba infection may not be recognized. Since an increase in the number of cases of Acanthamoeba infections has occurred worldwide, these protozoa have become increasingly important as agents of human disease

An epitope from Acanthamoeba castellanii that cross-react with proteolipid protein 139-151-reactive T cells induces autoimmune encephalomyelitis in SJL mice

“…Comparison of the incidence and EAE severity induced by PLP 139151 with that of ACA 83-95 revealed that ACA 83-95 induced clinical and/or histological EAE in only 72.7% of animals and the disease severity was mild ( Figure 2 and Table 2 (Marciano-Cabral and Cabral, 2003). In our studies with ACA 83-95, although MNC were present, the dominance of plasma cells and giant cells was absent.…”

“…ACA is a free-living organism present throughout the world habituating in water, soil, and dust, and it causes AGE, amoebic keratitis and cutaneous amoebiasis in infected humans (Claerhout and Kestelyn, 1999;Marciano-Cabral and Cabral, 2003). AGE is a chronic progressive disease of the CNS commonly seen in chronically ill, debilitated, or immunocompromised individuals such as AIDS patients (Marciano-Cabral and Cabral, 2003). The amoebae activate phosphatidylinositol 3-kinase to induce apoptosis of brain microvascular endothelial cells and successfully traverse the blood-brain barrier to induce AGE (Sissons et al, 2005).…”

A Rabbit Model of Acanthamoeba Keratitis That Better Reflects the Natural Human Infection

“…They have also been isolated from hydrotherapy baths, dental irrigation equipments, humidifiers, cooling systems, ventilators, and intensive care units (Marciano-Cabral et al, 2003). Acanthamoeba species can exist as either dormant cysts or as the active trophozoites (Khan et al, 2001).…”

Histopathologic spectrum and immunohistochemical diagnosis of amebic meningoencephalitis

“…21,22,25 Diagnostic techniques that do not rely on visualization of trophozoites, such as polymerase chain reaction, have been developed. 7,[26][27][28] As molecular techniques are being applied more frequently for diagnosis of a variety of infectious agents, falsepositive reactions will occur. Thus, molecular results have to be correlated with epidemiologic, clinical, and pathologic features.…”

“…5,6 Other diagnostic techniques, including microscopy of wet mounts, histopathology, electron microscopy, immunocytochemistry (such as immunofluorescence, flow cytometry), and culture, rely on identification of trophozoites and cysts in cerebrospinal fluid or brain tissue specimens. 1,7,8 Previous histopathologic reports describe single cases or small series of patients infected by one amebic genus. [9][10][11][12][13][14][15][16][17][18][19][20] Side-by-side histopathologic comparison of cases caused by different ameba is not available.…”