Isolation, Identification and Increasing Importance of 'Free-Living' Amoebae Causing Human Disease

Abstract

Amphizoic small amoebic protozoa are capable of existing both in 'free-living' and in 'parasitic' form depending on the actual conditions. Two genera (Naegleria and Acanthamoeba) have become recognised as opportunist human parasites. Since the first description in 1965 of a lethal case of primary amoebic meningoencephalitis (PAM) caused by Naegleria, many more (mostly lethal) cases have been reported, while granulomatous amoebic encephalitis (GAE), as well as eye (keratinitis, conjunctivitis, etc.), ear, nose, skin and internal organ infections caused by Acanthamoeba have also occurred in rapidly increasing numbers. Both pathogenic and non-pathogenic species of Naegleria and Acanthamoeba are found worldwide in water, soil and dust, where they provide a potential source of infection. Successful differential diagnosis and appropriate (specific) therapy depends on precise laboratory identification of the 'free-living' amoebae. In most cases, isolation from the environment can be achieved, but identification and differentiation of the pathogenic and non-pathogenic strains is not easy. The methods presently available do not fulfil completely the requirements for specificity, sensitivity and reliability. Morphological criteria are inadequate, while thermophilic character, pH dependency and even virulence in infected mice, are not unambiguous features of pathogenicity of the different strains. More promising are molecular methods, such as restriction endonuclease digestion of whole-cell DNA or mitochondria1 DNA, as well as iso-enzyme profile analysis after iso-electric focusing and staining for acid phosphatase and propionyl esterase activity. Use of appropriate monoclonal antibodies has also yielded promising results in the differentiation of human pathogenic and non-pathogenic strains. However, quicker, simpler, more specific and reliable methods are still highly desirable. The significance of endosymbiosis (especially with Legionella strains) is not well understood. The results of a systematic survey in Hungary for the isolation and identification of 'free-living' amoebae, including an investigation of the Hungarian amoebic fauna, the isolation of possibly pathogenic Naegleria strains and of some Acanthamoeba strains from eye diseases, as well as the finding of a case of endosymbiosis, are also reported here.

Isolation and morphotyping of Acanthamoeba spp. and Vermamoeba spp. from hospital air-conditioning systems

“…FLA have been isolated from samples obtained from environmental materials such as pools, lakes, thermal springs, domestic water supplies, soil, air, dust, air-conditioning units [1][2][3][4][5][6][7] . To our knowledge the presence of FLA in the environment does not mean a risk factor for illness.…”

“…Hem SYA hem de içlerinde taşıyabilecekleri endosimbiyontlarıyla ilgili riskleri azaltmak için havalandırma sistemleri düzenli olarak etkili dezenfektenlarla temizlenmelidir. [1][2][3][4] . They have been associated with infections of the central nervous system in humans [5][6][7] .…”

Random amplified polymorphic DNA profiles as a tool for the characterization of Brazilian keratitis isolates of the genus Acanthamoeba

“…In humans, some species have been implicated in different pathologies, including granulomatous amebic encephalitis (GAE), which occurs in immunologically depressed individuals, and keratitis, a severe and painful corneal infection mainly associated with the use of contact lenses (3,4).…”

Seasonal Meningoencephalitis in Holstein Cattle Caused by Naegleria Fowleri

“…5,15,18 Their cysts have even been demonstrated in dust during dust storms. 13 The habitat of Balamuthia is not known but is believed to be similar to that of Naegleria and Acanthamoeba. 8 Primary amoebic meningoencephalitis (PAM) is the term for the human disease caused by N. fowleri.…”