Human infections caused by free-living amoebae

Abstract

Introduction. Among free-living amoebae that are widely distributed in nature only four genera/species are known as agents of human infections: Acanthamoeba spp., Naegleriafowleri, Balamuthia mandrillaris and Sappiniapedata. These amoebae are not well adapted to parasitism, and could exist in the human environment without the need for a host. Infections due to these amoebae, despite low morbidity, are characterized by relatively high mortality rate and pose serious clinical problems. Objectve. This review study presents and summarizes current knowledge about infections due to pathogenic and opportunistic free-living amoebae focused on epidemiology, clinical manifestations, diagnosis and treatment based on global literature. State of knowledge. All four genera have been recognized as etiologic factors of fatal central nervous system infections and other serious diseases in humans. N. fowleri causes an acute fulminating meningoencephalitis in children and young adults. Acanthamoeba spp. and B.mandrillaris are opportunistic pathogens causing granulomatous amoebic encephalitis and disseminated or localized infections which could affect the skin, sinuses, lungs, adrenals and/or bones. Acanthamoeba spp. is also the main agent of acute eye infection -Acanthamoeba keratitis, mostly in contact lens wearers. However, there is only one recognized case of encephalitis caused by S. pedata. Conclusions. Amoebic diseases are difficult to diagnose which leads to delayed treatment, and result in a high mortality rate. Considering those issues, there is an urgent need to draw more attention to this type of diseases.

Genotyping and interaction-reality of Acanthamoeba, enteric adenovirus and rotavirus in drinking water, Egypt.

“…are the most common free-living amoebae have been isolated from a wide range of environments particularly water. Free-living amoebae have been reported to feed by phagocytosis on bacteria, fungi, and algae (Król-Turmińska and Olender, 2017;Chen et al, 2018). According to the previous reports (Scheid and Schwarzenberger, 2012;Yousuf et al, 2017), Acanthamoeba might serve as an environmental reservoir for viruses living in the same environment, such as mimivirus, coxsackievirus and adenovirus.…”

“…are the most common free-living protozoa, isolated from public water supplies, swimming pools, bottled water, distilled water bottles, ventilation ducts, the water-air interface, air-conditioning units, soil, beaches, vegetables, air, surgical instruments, and contact lenses, indicating the ubiquitous nature of these organisms (Cruz and Rivera, 2014;Todd et al, 2015;Al-Herrawy et al, 2015). Acanthamoeba species can cause various diseases such as keratitis and granulomatous amoebic encephalitis, which is often fatal in immune-compromised as well as immunocompetent patients (Król-Turmińska and Olender, 2017). The possible mode of transmission includes direct contact of contaminated water, inhalation of cysts or trophozoites of Acanthamoeba carried by the wind through the respiratory tract, improper contact lens-care practices, or direct skin contact by traumatic injection or entry through preexisting wounds or lesions.…”

A case report of granulomatous amoebic encephalitis by Group 1 Acanthamoeba genotype T18 diagnosed by the combination of morphological examination and genetic analysis

“…A previous report indicated that only a few drugs have demonstrated in vitro activity against Acanthamoeba and have resulted in the successful treatment of a few patients: azoles, rifampicin, pentamidine, sulfadiazine, azithromycin, caspofungin, etc. [ 13 ]. The clinical usefulness of subclassification of Acanthamoeba also remains unknown at this time.…”

Answer to May 2019 Photo Quiz

“…In the context of immunodeficiency, Acanthamoeba can cause a central nervous system infection called granulomatous amebic encephalitis or may disseminate to multiple organ systems. Disseminated infections usually occur in solid organ transplant recipients, AIDS patients, or patients with hematological malignancies (4). Acanthamoeba infections have rarely been reported to occur in lung transplant recipients, and to our knowledge, only nine other cases have been reported in this setting (5,6).…”