Acanthamoeba Strains Research Articles

Pathogenic and nonpathogenic Acanthamoeba spp. in thermally polluted discharges and surface waters.

During spring and autumn, the total number of amoebae and the number of acanthamoeba species able to grow at 37 degrees C were determined in six thermally polluted factory discharges and the surrounding surface waters. The isolated Acanthamoeba strains were studied for growth in axenic medium, cytopathic effect in Vero cell cultures, and virulence in mice. Although more amoebae were isolated in autumn, the number of Acanthamoeba species was lower than in spring, when the percent of pathogenic strains among the isolates was highest. Higher concentrations of amoebae were found in warm discharges, and more virulent strains occurred in thermal discharges than in surface waters.

Growth characteristics, cytopathic effect in cell culture, and virulence in mice of 36 type strains belonging to 19 different Acanthamoeba spp.

A total of 36 strains belonging to 19 different species of Acanthamoeba were compared for temperature tolerance, ability to grow in an axenic medium, cytopathic effect in Vero cell culture, and virulence in mice. Pathogenic strains appeared to belong to different species, whereas pathogenic and nonpathogenic strains occurred in one species. Although growth at high temperatures and readiness to grow axenically indicated a potential for pathogenicity, each such strain had to be tested in cell cultures or laboratory mice to determine whether or not it was virulent. This study was not intended to differentiate Acanthamoeba spp., but to provide methods to be used for the specific isolation and identification of pathogenic Acanthamoeba strains.

ISOLATION, DISTRIBUTION AND DISEASE POTENTIAL OFNAEGLERIAANDACANTHAMOEBA(ORDER: AMOEBIDA) IN SOUTH AFRICA

Summary During the period January 1971 to July 1976, over 240 strains of Naegleria, Acanthamoeba and other limax amoebae were isolated from a variety of habitats in South Africa and South West Africa. Seven strains of Naegleria fowleri and a strain of Acanthamoeba were isolated from a heavily polluted section of the Eerste River, Cape Province, South Africa. These 8 isolates have been identified as being potentially pathogenic, the first such report for Africa. Limax amoebae have been discovered in previously undescribed habitats. Naegleria was found in marine mud and Acanthamoeba was isolated from desert sand. Both Naegleria and Acanthamoeba have been found in the alimentary tract of the clawed toad Xenopus laevis and in the faeces of the black duck Anas sparsa. These animals may act as vectors for the transmission of limax amoebae from one site to another.

The Suitability of Starch-Gel Electrophoresis of Esterases and Acid- Phosphatases for the Study of Acanthamoeba Taxonomy

Summary The esterases and acid -phosphatases of 32 strains of Acanthamoeba were compared using the technique of starch-gel electrophoresis.The enzyme mobility patterns allowed an arrangement of the strains in twelve clearly distinguishable groups.The enzyme patterns were found to be consistent and stable with no variation occurring during logarithmic growth in batch culture.Strains which had originated from the same isolate gave similar patterns even though they had been maintained separately for as much as twenty years. Many of the strains which had been assigned to the same species using morphological criteria showed different enzyme patterns.The species A.castellanii, which was represented by seven strains, could be assigned to four groups on the basis of their enzyme patterns.Similarly, the four strains of A.polyphaga also exhibited four distinct enzyme patterns.Two of the enzyme groups consisted of strains from more than one morphological species. These results suggest that the morphological criteria which have been used to classify Acanthamoeba are not adequate for resolving taxa at the species level.

Isolation and Experimental Infection of Free-Living Amebae in Freshwater Fishes

Twenty-three species of fish from nine southeastern states were screened for the presence of small, free-living amebae. Organs from 11 species of fish contained amebae of the genera Acanthamoeba, Naegleria, and Vahlkampfia. Three strains of Acanthamoeba were injected into fish to determine infectivity and pathogenicity of the amebae. Strains used were an A. polyphaga MC-1 isolated from the spleen of a bass, the pathogenic A-5 strain of A. culbertsoni, and the pathogenic Lilly A-1 strain of A. culbertsoni. The MC-1 strain established systemic infections in many organs of the test fish. The 2 strains of A. culbertsoni did not produce any infection in fish under the laboratory conditions.

Chemotherapeutic compounds and Acanthamoebae from eye infections.

The amoebicidal and amoebistatic action in vitro of 24 compounds was tested on two strains of Acanthamoeba, A. polyphaga and A. castellanii, isolated from eye infections in this country. For comparison, the Ryan strain of A. castellanii and Naegleria gruberi L-1 were also examined. Nine compounds showed sufficient activity to merit further consideration, ie, acriflavine, proflavine, hydroxystilbamidine isethionate, paromomycin, miconazole, amphoterin, neomycin, polymyxin, and the last two combined in Neosporin.

Differences in destruction of cysts of pathogenic and nonpathogenic Naegleria and Acanthamoeba by chlorine

The destructive action of chlorine on the pathogenic Naegleria fowleri and Acanthamoeba culbertsoni, the nonpathogenic N. gruberi, and an avirulent Acanthamoeba isolate was investigated. N fowleri is somewhat more sensitive to chlorine than N. gruberi, whereas the two Acanthamoeba strains are very resistant. This study yields information needed for the destruction of amoebic cysts in drinking water and swimming pools. It also gives some explanation for the occurence of Acanthamoeba strains in these waters.

Comparative Studies on Related Free‐Living and Pathogenic Amebae With Special Reference to Acanthamoeba*

Comparative studies were conducted on the structure, nutrition, protein composition, immunology, and effect on cell cultures of Acanthamoeba sp. (Lilly A-1 strain), A. castellanii (Singh and Neff strains), A. astronyxis, A. comandoni, A. polyphaga, A. terricola, Hartmannella vermiformis, and Naegleria gruberi. Lilly A-1 strain of Acanthamoeba received special attention owing to its pathogenicity for experimental animals. Distinct differences were noted in structure, nutrition, and antigenic composition of Acanthamoeba spp. and Hartmannella, and it was concluded that their recognition as separate genera is justified. With the exception of A. terricola, all species of Acanthamoeba could be differentiated by cyst structure. Cysts of A. terricola closely resembled those of A. castellanii Singh strain, and close antigenic relationships between these 2 species were demonstrated by gel diffusion and immunoelectrophoresis (IEP); it was concluded that the 2 amebae belong in the same species. The pathogenic Acanthamoeba sp, Lilly strain differed from the nonpathogenic A. castellanii Singh strain (a) cyst structure; (b) protein distribution patterns (on disc electrophoresis);(c)soluble and particulate antigens (on gel diffusion, IEP, complement fixation, and immobilization tests); (d) capacity to induce cell-free plaques and other cytopathic effect (CPE) in mammalian monlayer cell cultures; (e) elimination of a phospholipase, responsible for some of the CPE, into the culture medium. Acanthamoeba sp. Lilly strain, which liberated more phospholipase, produced more CPE. Acanthamoeba sp. Lilly strain differed also from other species of this genus in cyst structure and antigenic composition. It was concluded, therefore, that, following the recommendation of Singh & Das, it ought to be placed in a separate species, Acanthamoeba culbertsoni.

Concanavalin A-induced agglutination of Acanthamoeba.

VIRULENT strains of Acanthamoeba produce cytopathic effects in mammalian tissue cultures1–3, and cause acute meningoencephalitis in laboratory animals after intranasal inoculation1. In humans, Acanthamoeba seem to produce cerebral lesions in defence-weakened individuals4–7. We have begun studies of the cell surface of Acanthamoeba since virulent strains must make direct contact with a host cell before initiation of degenerative changes in mammalian tissue cultures2,3. The sensitivity of avirulent and virulent strains to concanavalin A (con A)-induced agglutination was investigated first as there was no evidence that carbohydrate-containing components were exposed at the cell surface of Acanthamoeba. Our results indicate that both avirulent and virulent Acanthamoeba were sensitive to con A-induced agglutination. In contrast to the results of studies of avirulent and virulent Entamoeba histolytica8, however, the avirulent strain was more sensitive to con A.

The influence of growth medium on axenic cultivation of virulent and avirulent Acanthamoeba.

SummaryThe growth characteristics are described for two strains of pathogenic Acanthamoeba cultured in an axenic, peptone-based medium under aerated suspension conditions. The highly virulent A-1 amebae grew exponentially with a constant generation time of 8–9 hr to densities of 2.5–3.5 × 106 cells/ml. The HN-3 chronically virulent strain, whose growth medium was enriched with serum, exhibited a generation time of 10–11 hr and attained exponential densities of 1–2 × 106 cells/ml. Encystment readily occurred in stationary phase cultures of HN-3 cells, but not in A-1 cultures. A comparison was made of the growth parameters of the pathogenic Acanthamoeba to the nonpathogenic Neff strain cultured under similar conditions.

Observations on induced amitosis in Acanthamoeba

Methods are described for the induction of amitotic cell division in Acanthamoeba rhysodes. Induced amitotic cell division in this organism is similar to normal cytokinesis in many respects, however, the nucleus is partitioned during its interphase state so that the daughter products of amitosis are not viable. It is proposed that the induction of amitotic cell division causes the amoeba to produce the normal cytoplasmic components responsible for cell division in the absence of nuclear mitosis. This is not a normal stage in the amoeba's life cycle and it appears to be a genetic defect unique to this strain of Acanthamoeba. Evidence is presented that induction of amitotic cell division requires protein synthesis but not ribonucleic acid synthesis. Further, induced amoebae require a period of adhesion to a foreign substrate before they are capable of amitosis. The pattern of amitotic cell division could be interpreted as a segregation of discrete cytoplasmic units, generated during induction.

Gastrointestinal Parasitism in the Dog

Acanthamoeba culbertsoni trophozoites, previously isolated from a human keratitis case with severe intraocular damage, were maintained in axenic culture. Co-incubation of amoebae with MDCK cell monolayers demonstrated an apparent preference of the amoebae to introduce themselves between the cells. The trophozoites appeared to cross the cell monolayer through the tight junctions, which resulted in decreased trans-epithelial resistance (TER) measurements. Unexpectedly, after co-incubation of amoebae with hamster corneas, we observed that the trophozoites were able to cross the different cell layers and reach the corneal stroma after only 12 h of interaction, in contrast to other Acanthamoeba species. These observations suggest that this A. culbertsoni isolate is particularly pathogenic. Further research with diverse methodologies needs to be performed to explain the unique behavior of this Acanthamoeba strain.

Re-definition of the genus Acanthamoeba with descriptions of three species.

SYNOPSIS. Ten strains of Acanthamoeba from freshwater habitats were isolated in clonal cultures. Studies were made of trophic structure, nuclear division, cyst structure, some aspects of cytochemistry, and other characteristics. One strain was identified as A. castellanii (Douglas, 1930), one as A. astronyxis (Ray and Hayes, 1954), and 8 as A. polyphaga (Puschkarew, 1913). Strains of Acanthamoeba isolated by other workers were also examined comparatively.The pattern of nuclear division in all strains resembled that in metazoan cells, with the exception that centrioles were never found. Trophic amoebae had a PAS‐positive surface outline. Cyst walls were strongly PAS‐positive and also gave a positive test for cellulose with zinc chloroiodide.The genus Acanthamoeba Volkonsky, 1931 is re‐defined, being distinguished from Hartmannella Alexeieff, 1912, emend. Volkonsky, chiefly by the formation of tapering, hyaline pseudopods (acanthopodia) and by a cyst made up of an ectocyst and a polyhedral or stellate endocyst, with excystment by removal of opercula. Other characteristics found in all strains include a distinctive food cup, the presence of many small refractile globules in the cytoplasm of trophic amoebae, and a cyst wall containing cellulose. The degree of spindle convergence, employed by Volkonsky as a generic criterion, was unusable.Differential diagnoses based principally on cyst structure are offered for A. castellanii, A. astronyxis, and A. polyphaga. The strain previously called Mayorella palestinensis Reich, 1933 is a distinct species of Acanthamoeba.

Selective phagocytosis of nucleated erythrocytes by cytotoxic amebae in cell culture.

Strains of Acanthamoeba, which produce cellular damage resembling viral cytopathic effect, are known to occur in cultures of monkey kidney cells. Trophozoites of a similar strain were observed to engulf and denucleate chicken erythrocytes. Nonnucleated guinea pig erythrocytes were apparently left unchanged.