Efficient Liquid Media for Encystation of Pathogenic Free-Living Amoebae

Pathogenic Naegleria fowleri, Acanthamoeba castellanii, and Acanthamoeba polyphaga, are distributed worldwide. They are causative agents of primary amoebic meningoencephalitis or acanthamoebic keratitis in humans, respectively. Trophozoites encyst in unfavorable environments, such as exhausted food supply and desiccation. Until recently, the method of N. fowleri encystation used solid non-nutrient agar medium supplemented with heat-inactivated Escherichia coli; however, for the amoebic encystment of Acanthamoeba spp., a defined, slightly modified liquid media is used. In this study, in order to generate pure N. fowleri cysts, a liquid encystment medium (buffer 1) modified from Page’s amoeba saline was applied for encystation of N. fowleri. N. fowleri cysts were well induced after 24 hr with the above defined liquid encystment medium (buffer 1). This was confirmed by observation of a high expression of differential mRNA of nfa1 and actin genes in trophozoites. Thus, this liquid medium can replace the earlier non-nutrient agar medium for obtaining pure N. fowleri cysts. In addition, for cyst formation of Acanthamoeba spp., buffer 2 (adjusted to pH 9.0) was the more efficient medium. To summarize, these liquid encystment media may be useful for further studies which require axenic and pure amoebic cysts.

A method for microbial decontamination of Acanthamoeba cultures using the peritoneal cavity of mice

Objective: To evaluate whether the inoculation of contaminated cultures in the peritoneal cavity of mice could implement decontamination of Acanthamoeba cultures. Methods: Suspensions of Acanthamoeba, Acanthamoeba polyphaga ATCC 30461, or Acanthamoeba spp. isolated from soil (UnB13 strain) were inoculated in the peritoneal cavity of Swiss mice (. n = 24). After 1, 6, 12, or 24 h of exposure the peritoneal cavity was washed and assessed for the presence of bacteria, fungi, and Acanthamoeba. Results: After 1 h of intraperitoneal inoculation at least 97% of the bacteria and 96% of the fungi ( P < 0.05) and 99% of the bacteria ( P < 0.05) were successfully eliminated from the ATCC 30461 strain and from the soil isolate UnB13 strain, respectively. This method also allowed the recovery of most trophozoites and cysts from both Acanthamoeba cultures at the end of 24 h. Conclusions: Our data demonstrated that this technique has great potential for decontamination of Acanthamoeba cultures in a short period of time.

A method for microbial decontamination ofAcanthamoeba cultures using the peritoneal cavity of mice

Objective:To evaluate whether the inoculation of contaminated cultures in the peritoneal cavity of mice could implement decontamination ofAcanthamoeba cultures. Methods: Suspensions ofAcanthamoeba,Acanthamoeba polyphagaATCC30461, or Acanthamoeba spp. isolated from soil (UnB13 strain) were inoculated in the peritoneal cavity of Swiss mice (n = 24). After 1, 6, 12, or 24 h of exposure the peritoneal cavity was washed and assessed for the presence of bacteria, fungi, andAcanthamoeba. Results: After 1 h of intraperitoneal inoculation at least 97% of the bacteria and 96% of the fungi (P Conclusions: Our data demonstrated that this technique has great potential for decontamination ofAcanthamoeba cultures in a short period of time.

In vitro effect of Acanthospermum australe (Asteraceae) extracts on Acanthamoeba polyphaga trophozoites / Efeito in vitro de extratos de Acanthospermum australe (Asteraceae) sobre trofozoitos de Acanthamoeba polyphaga

Acanthamoeba is a free-living protozoan widely distributed in the environment, occurring in vegetative trophozoite and resistance cyst stages during its life cycle. It constitutes an etiological agent of Acanthamoeba keratitis, a disease that may cause severe ocular inflammation and blindness. New drugs can be developed from molecules found in plants and thus help in its difficult treatment. Acanthospermum australe (Asteraceae), a plant used in folk medicine, had its effect tested on Acanthamoeba polyphaga. Aqueous and ethanolic extracts of A. austral were obtained from aerial parts for infusion and static maceration, respectively. Concentrations of 10, 5, 2.5, 1.25 and 0.625 mg/ml of the extract were tested against Acanthamoeba polyphaga trophozoites. The cytotoxic effect of the extracts was tested in mammalian cells using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. RESULTS: The 10 mg/ml concentration of ethanolic extract was lethal to 100% of the A. polyphaga trophozoites in 24 h and both extracts presented cytotoxic effect against mammalian cells. These findings suggest that the A. austral ethanolic extract may have compounds with relevance to the development of new amoebicidal drugs.

Acanthamoeba é um protozoário de vida livre amplamente distribuído no ambiente, ocorrendo sob a forma trofozoítica (metabolicamente ativa) e cística (de resistência), durante seu ciclo de vida. O protozoário constitui um agente etiológico da Ceratite Amebiana, uma doença que pode causar inflamação ocular severa e cegueira. Novos fármacos podem ser desenvolvidos a partir de moléculas encontradas em plantas e assim ajudar em seu difícil tratamento. Aqui, Acanthospermum australe (Asteraceae), uma planta utilizada na medicina popular, teve seu efeito sobre trofozoítos de Acanthamoeba polyphaga testado. O extrato aquoso e etanólico de A. australe foram obtidos das partes aéreas por infusão e maceração estática, respectivamente. As concentrações 10, 5, 2,5, 1,25 e 0,625 mg/ml dos extratos foram testadas contra trofozoítos do protozoário. O efeito citotóxico dos extratos foi testado em células de mamífero utilizando o ensaio de brometo de 3-[4,5-dimetiltiazol-2-il]-2,5-difeniltetrazólio (MTT). A concentração de 10 mg/ml do extrato etanólico foi letal a 100% dos trofozoítos de A. polyphaga em 24 h e ambos os extratos apresentaram efeito citotóxico contra as células de mamífero. Estes resultados sugerem que o extrato etanólico de A. australe pode ter componentes com relevância para o desenvolvimento de novos fármacos amebicidas.

ON ELECTROPHORETIC KARYOTYPE OF ACANTHAMOEBA POLYPHAGA / 中国寄生虫学与寄生虫病杂志

An electrophoretic karyotype of Acanthamoeba polyphaga has been preliminarily analysed by means of pulse field gel electrophoresis (PFGE).Ten chromosomal DNA bands are distinguishable on the gel.Using yeast (Saccharomyces cerevisiae) chromosomal DNA as size standard,we estimate the size of the chromosomes to be between about 200 kilobase pairs (kb) and 2 megabase pairs (mb).