Comparison of physiological, cytopathogenic and immunological properties between two environmental isolates of Acanthamoeba spp.

The aim of this study was to determine whether pathogenic and less-pathogenic isolates of environmental Acanthamoeba exhibit differences in adhesion to human erythrocytes. Based on physiological properties of temperature, tolerance, and rapid growth, Acanthamoeba were divided into pathogenic and less-pathogenic isolates. Acanthamoeba were tested for their ability to produce cytopathic effects (CPE) using two human cell lines, HEp-2 and KB cells. Both ameba isolates caused CPE to both cell lines with the same pattern without significant difference. Human erythrocytes from 20 healthy volunteers were used to study the erythrocyte reactivity of Acanthamoeba by co-incubation with trophozoites. The pathogenic Acanthamoeba exhibited significantly higher erythrocyte adhesion as compared to the less-pathogens (p<0.05). Erythrocyte activity occurred in the presence of plasma in all blood samples, suggesting the role of plasmatic components and contact-dependent mechanisms to produce host cell cytotoxicity. The present results showed correlation between the physiological properties and erythrocyte reactivity of Acanthamoeba.

Factors affecting the hatching of human pinworm ova.

Parasite life-history traits reflect past environmental and host selective pressure that act to produce strategies that maximize successful transmission. Pooled human pinworm eggs were pretreated with 0.9% NaCl, acid digestive enzyme, and alkaline solutions (pH 9.0) and then incubated in 0.9% NaCl at room temperature and 37 degrees C both with and without 5% CO2. Eggs pretreated with both acid and base had the same hatching pattern, which was markedly different to that of the untreated eggs. At room temperature (RT), hatching of the pretreated eggs occurred on the first day and reached its peak rate (>90%) on day 3; at 37 degrees C hatching occurred on the second day and was more than 80% by day 5. Hatching of the untreated eggs was evident on day 2 at RT and between days 3-5 at 37 degrees C although in smaller numbers (<20%). The CO2 did not affect the hatching of larvae. The larvae could survive after hatching in 0.9% NaCl for 2 and 4 days at 37 degrees C and 25 degrees C, respectively. The present investigation gives a different information that human pinworm ova can hatch into larvae with or without exposure to acid digestive enzyme or alkaline solutions.

In vitro effect of artesunate against Acanthamoeba spp.

The in vitro effects of artesunate, the antimalarial agent, and metronidazole against Acanthamoeba spp were studied. Acanthamoeba Group II and Acanthamoeba polyphaga-like were isolated from natural water courses in Buri Ram Province, northeastern Thailand. The trophozoites were axenically cultured in PPYG medium and treated with artesunate in a concentration of 5-700 microg/ml. Artesunate showed its ability to inhibit the growth of acanthamoeba trophozoites: 54% at 50 mg/ml (after six days of exposure) and 93.2% at 100 microg/ml (after two days). The 500-700 microg/ml concentration caused inhibition on the first day of more than 93.2%; excystation did not occur in drug-treated medium. The present study shows that artesunate is amebastatic rather than amebicidal in an axenic culture of trophozoites at the highest concentration of 100 microg/ml. Metronidazole, in concentrations of 5-1,000 microg/ml, had no effects on either trophozoites or cysts.