Free-living amoebae infecting freshwater and marine fish include those described thus far as agents of fish diseases, associated with other disease conditions and isolated from organs of asymptomatic fish. This survey is based on information from the literature as well as on our own data on strains isolated from freshwater and marine fish. Evidence is provided for diverse fish-infecting amphizoic amoebae. Recent progress in the understanding of the biology of Neoparamoeba spp., agents responsible for significant direct losses in Atlantic salmon and turbot industry, is presented. Specific requirements of diagnostic procedures detecting amoebic infections in fish and taxonomic criteria available for generic and species determination of amphizoic amoebae are analysed. The limits of morphological and non-morphological approaches in species determination are exemplified by Neoparamoeba, Vannella and Platyamoeba spp., which are the most common amoebae isolated from fish gills, Acanthamoeba and Naegleria spp. isolated from various organs of freshwater fish, and by other unique fish isolates of the genera Nuclearia, Thecamoeba and Filamoeba. Advances in molecular characterisation of SSU rRNA genes and phylogenetic analyses based on their sequences are summarised. Attention is particularly given to specific diagnostic tools for fish-infecting amphizoic amoebae and ways for their further development.
A variety of conditions of cryopreservation were evaluated in order to define a single procedure for freezing the amebae of pathogenic Naegleria and Acanthamoeba. The average best conditions for freezing the three species studied were; lxlO1’ exponentially growing amebae/ml of freezing medium consisting of 12% dimethylsulfoxide, 20% heat-inactivated bovine calf serum, 4% glucose, in Mix ameba medium; 30 min equilibration at 23” С (room temperature), followed by 60 min at -20° C, with storage at -70° C. Under these conditions viability after 1 month of freezing was 53% for Acanthamoeba castellami, 64% for Naegleria fowleri, and 66% fot Naegleria australiensis. After 12 months of freezing, viability was 39% for A. castellami, 47% for N. fowleri, and 53% for N. auslraliensis.
The genus Acanthamoeba includes more than 20 morphological species, but classification is problematical. Recently, the discovery of substantial interstrain differences in ribosomal DNA (rDNA) sequences has prompted questions about the relatedness of strains of the same species. In this study, therefore, we have investigated relationships between two isolates of A. polyphaga, CCAP 1501/3c and ATCC 30871, using morphological, biochemical, physiological, molecular and cytotoxicity assays. We observed that A. polyphaga ATCC 30871 exhibited up to six arms in endocyst while A. polyphaga CCAP 1501/3c exhibited a maximum of 5 arms thus indicating their position in group 2 and 3, respectively. Acanthamoeba polyphaga ATCC 30871 exhibited growth at 37°C and growth on 1M mannitol plates while A. polyphaga CCAP 1501/3c did not. In addition, both isolates exhibited differences in isoenzyme banding patterns and rDNA restriction fragment polymorphisms. More importantly, A. polyphaga ATCC 30871 produced cytotoxicity on corneal epithelial cells while A. polyphaga CCAP 1501/3c had no effects, suggesting differences in pathogenicity. Thus, all the results provide evidence for significant differences between the strains and further provided the basis for reclassification of the isolates. Implications of these results in the clinical diagnosis of pathogenic Acanthamoeba are discussed.
Some free-living amoebae are a potential threat to human health. The best known species are those of the genus Acanthamoeba Volkonsky, 1931, which cause Acanthamoeba keratitis, granulomatous amoebic encephalitis and other forms of tissue inflammation. The aim of the present study was to search for potential pathogenic genotypes of free-living amoeba in the sand in children's playgrounds. Our results confirmed that free-living amoebae were present in all examined playgrounds. Sequences of the 18S rDNA have shown that all isolated potentially pathogenic strains of amoebae belong to genotype T4 of Acanthamoeba. The potential pathogenicity of isolates was confirmed on mice. The presence of pathogenic amoebae in the examined sand may be a potential source of human infection., Marcin Cholewiński, Piotr Solarczyk, Monika Derda, Agnieszka Wojtkowiak-Giera, Edward Hadaś., and Obsahuje bibliografii
Several conditions of isolation were evaluated to determine which yielded the greatest number of thermotolerant and pathogenic freeliving amebae. Swab samples, easier to obtain and process, produced more pathogenic amebae than water samples. If water samples are required, 50-ml volumes gave the greatest percentage of pathogenic isolates. An incubating temperature of 42"C yielded the most thermotolerant amebae. A total of 11 pathogenic isolates were obtained from 762 environmental samples and were Acanthamoeba (55 %), Naegleria fowleri Carter, 1970 (27 %), and N. australiensis De Jonckheere, 1981(18%).
This is a followup report on the viability of pathogenic Acanthamoeba castellami, Naegleria australiensis, and N. fowleri during 5 years of cryopreservation and the virulence of N. fowleri during 30 months of cryostorage, all at -70’C. The greatest decrease in viability occurred during the first year of freezing and was 10-fold greater than the average yearly decrease during years 2-5. At 5 years of cryostorage, viability was 33 % for A. castellana, 38 % for N. fowleri and 51% for N. australiensis. Virulence of N. fowleri did not decrease during 30 months of freezing and what appeared to be an increase in virulence during cryopreservation may be the result of reduced viability of the less virulent amebae in a culture.