Growth and Encystation of Acanthamoeba castellanii

Chagla, Abdul H.; Griffiths, A. Phillips

doi:10.1099/00221287-85-1-139

Cited by 41 publications

(27 citation statements)

References 11 publications

(12 reference statements)

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“…4) composed of an ectocyst and an endocyst ranges in size from 13 to 20 m and varies from species to species (46). Cyst formation occurs under adverse environmental conditions such as food deprivation, desiccation, and changes in temperature and pH (46,60,76). Villemez and coworkers (457,484) have reported that antibody binding to a specific membrane protein also causes A. castellanii to encyst.…”

Section: Morphologymentioning

confidence: 99%

Acanthamoebaspp. as Agents of Disease in Humans

2003

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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

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Section: Morphologymentioning

confidence: 99%

Acanthamoebaspp. as Agents of Disease in Humans

2003

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“…One such organism is the common soil protozoon Acanthamoeba castellanii. This organism is vital for maintaining soil bacteria at relatively constant levels [15]. To do this it must be able to phagocytose and lower environmental temperatures may impede this process by causing membrane lipids to be below their transition temperature.…”

Section: Poikilotherms At the Mercy Of The Environmentmentioning

confidence: 99%

Inspired by lipids: the Morton Lecture Award Presentation

Harwood

2017

Biochemical Society Transactions

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“…Cysts were obtained by adding MgClz (final concentration 50 mM) to cultures which had been grown in PGY for 5 d at 30 "C in a shaking water-bath (Chagla & Griffiths, 1974). After further incubation for 2 d, 5 ml portions were centrifuged aseptically at 500 g for 5 d n .…”

Section: E T H O D Smentioning

confidence: 99%

The Use of Physiological Characterizations in the Classification of Five Species of Acanthamoeba

Griffiths

Curnick

Unitt

et al. 1978

Journal of General Microbiology

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Physiological tests were devised and used to compare 15 strains representing five species of soil and freshwater amoebae assigned to the genus Acanthamoeba. The tests gave an acceptable level of reliability and the pattern of responses was not affected by the differing growth rates of the organisms. There was some degree of overlap between the strains, as shown by the high level of inter-species similarities in relation to those between strains of the same species. Previous classifications of Acanthamoeba, which are based solely on morphological criteria, do not adequately reflect the diversity of these amoebae. I N T R O D U C T I O NSmall amoebae, variously assigned to the genera Acanthamoeba, Hartmannella and Mayorella, occur widely in soil and aquatic habitats and are probably some of the most common protozoa (Page, 1967(Page, , 1976. Some cause certain pathological conditions (Culbertson, 1971). As they are one of the few groups of protozoa which can be isolated and grown in axenic culture they are also being used increasingly in fundamental studies of cell physiology and biochemistry. However, their ecological relationships are poorly understood, due, in part, to the confusion of some of the existing classifications of the group which are based entirely on morphological criteria.At present the most important taxonomic characters are: pseudopodial form; type of amoeboid movement; occurrence of a flagellate stage in the life-cycle; nuclear structure; cyst morphology and method of excystation. The use of such characters can be criticized on several grounds, for example, descriptions of pseudopodial form are often imprecise and cyst morphology can be extremely variable or modified significantly by the environment (Pussard, 1966;Stratford & Griffiths, 1978).The DNA base compositions of representative strains range from 50 to 62 yo GC (Adam & Blewett, 1974) suggesting that existing classifications may not adequately reflect the diversity of this group of organisms. Physiological characters could be used more extensively (Adam, 1964b), and in this present study, methods have been devised to examine further the physiological diversity of 15 strains of amoebae now included in the genus Acanthamoeba. M E T H O D SStrains and their routine maintenance. Fifteen strains representing five species of Acanthamoeba were examined (Table 1). All cultures were axenic and, after receipt, were maintained in PGY medium [0.75 % (w/v) peptone, 0.75 % (w/v) yeast extract, 1.5 % (w/v) glucose; Difco or Oxoid peptones and yeast extracts could be used in this medium with equal effect]. Stock cultures (5 ml) were kept at laboratory temperature in small, screw-capped bottles. These were inoculated with 0.5 ml of a culture which had been maintained similarly and subcultures were made every 4 to 6 weeks.Tests used to characterize cultures of trophozoites. Tests devised for this study are listed in Table 2. PGY

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Growth and Encystation of Acanthamoeba castellanii

Cited by 41 publications

References 11 publications

Acanthamoebaspp. as Agents of Disease in Humans

Acanthamoebaspp. as Agents of Disease in Humans

Inspired by lipids: the Morton Lecture Award Presentation

The Use of Physiological Characterizations in the Classification of Five Species of Acanthamoeba

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