Acanthamoeba Spp Research Articles

Phenothiazine compounds inhibit in vitro growth of pathogenic free-living amoebae.

The phenothiazine compounds trifluoperazine dihydrochloride and chlorpromazine hydrochloride have in vitro activity against the pathogenic free-living amoebae Naegleria fowleri, Acanthamoeba culbertsoni, and Acanthamoeba polyphaga. Drug concentrations of 10 microM were amoebastatic; concentrations of 50 microM were either amoebastatic or amoebicidal. Concentrations of 100 microM were generally amoebicidal. The mechanism of drug action is unclear. It may reflect sensitivity of amoeba calcium regulatory protein to the phenothiazine compounds or may be due to the lipophilic action of the drugs on the amoeba plasma membrane. Accumulation of these drugs in the central nervous system makes them potentially useful chemotherapeutic agents in humans for treatment of amoebic meningoencephalitis caused by N. fowleri and Acanthamoeba spp.

Subacute and chronic meningoencephalitis in mice after experimental infection with a strain of Naegleria fowleri originally isolated from a patient.

Swiss mice were inoculated intranasally with trophozoites of a cloned substrain of the Naegleria fowleri strain LL originally isolated from a human being. The original strain had decreased in virulence after ten years of maintenance in axenic culture. survivors were sacrificed from the fourth to the tenth week p.i. They were tested in a labyrinth experiment in which some demonstrated a diminution in performance. N. fowleri could be reisolated from the brains of five clinically inconspicuous animals. The histopathological findings in the brains of these animals resembled the features of a chronic granulomatous amebic encephalitis (GAE) which has been described in infections due to Acanthamoeba spp. It was not expected that N. fowleri could also produce latent infections. The significance of these findings is discussed.

Immunity to pathogenic free-living amoebae: role of humoral antibody.

Pathogenic free-living amoebae are common in nature, but few clinical infections by these amoebae have been reported. This has prompted studies of host susceptibility factors in humans. A survey of normal human sera from three New Zealand Health Districts was made; antibodies to pathogenic free-living amoebae were found in all sera, with titers ranging from 1:5 to 1:20 for Naegleria spp. and from 1:20 to 1:80 for Acanthamoeba spp. The antibodies belonged mainly to immunoglobulin G and immunoglobulin M classes. The presence of a specific neutralizing factor against Acanthamoeba spp. but not Naegleria spp. was demonstrated. Possible protective mechanisms are discussed.

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.