Search

Free-living amoebae (FLA) are widely distributed protozoa in both natural and artificial environments such as drinking water. In addition to the ability of all FLA to transport various pathogenic microorganisms, certain species, such as Acanthamoeba spp. or Balamuthia mandrillaris, have intrinsic pathogenic abilities and cause severe cerebral infections. Previous work has shown an enrichment of FLA cysts in biofilm developed in upper levels of Drinking Water Storage Towers (DWSTs), suggesting that differences in densities of FLA cysts may play a role in their unequal distribution in the water column. To evaluate this hypothesis, a model of a water column was created for this study and used to analyze the vertical distribution of cysts of the FLA Acanthamoeba castellanii, Vermamoeba vermiformis, and Balamuthia mandrillaris from 0 to 23 weeks. Interestingly, our data showed that the cysts of both A. castellanii and V. vermiformis were enriched in upper water levels during their aging. However, B. mandrillaris cysts were equally distributed in the water column during the entire study. These results show that, in addition to the role of water level variation in the DWST, some FLA cysts can become less dense during their aging, which contributes to their enrichment in upper water and therefore biofilm levels. [ABSTRACT FROM AUTHOR]

Free-living amoebae (FLA) are widely distributed protozoa in both natural and artificial environments such as drinking water. In addition to the ability of all FLA to transport various pathogenic microorganisms, certain species, such as Acanthamoeba spp. or Balamuthia mandrillaris, have intrinsic pathogenic abilities and cause severe cerebral infections. Previous work has shown an enrichment of FLA cysts in biofilm developed in upper levels of Drinking Water Storage Towers (DWSTs), suggesting that differences in densities of FLA cysts may play a role in their unequal distribution in the water column. To evaluate this hypothesis, a model of a water column was created for this study and used to analyze the vertical distribution of cysts of the FLA Acanthamoeba castellanii, Vermamoeba vermiformis, and Balamuthia mandrillaris from 0 to 23 weeks. Interestingly, our data showed that the cysts of both A. castellanii and V. vermiformis were enriched in upper water levels during their aging. However, B. mandrillaris cysts were equally distributed in the water column during the entire study. These results show that, in addition to the role of water level variation in the DWST, some FLA cysts can become less dense during their aging, which contributes to their enrichment in upper water and therefore biofilm levels.

Acanthamoeba is a free-living protozoan known to cause keratitis most commonly, especially among contact lens wearers. Treatment of Acanthamoeba keratitis is challenging as Acanthamoeba can encyst from the active form, a trophozoite, into a hibernating cyst that is refractory to antibiotics and difficult to kill; therefore, there is a need for more effective anti-amoebic strategies. In this study, we have evaluated the anti-amoebic activity of the antimicrobial peptide mimic RK-758 against Acanthamoeba castellanii. RK-758 peptidomimetic was subjected to biological assays to investigate its amoebicidal, amoebistatic, anti-encystation, and anti-excystation effects on A. castellanii. The anti-amoebic activity of the peptide mimic RK-758 was compared with chlorhexidine against the Acanthamoeba castellanii ATCC30868 and Acanthamoeba castellanii 044 (a clinical strain) with the concentrations of both ranging from 125 µM down to 7.81 µM. All experiments were performed in duplicate with three independent replicates. The data were represented as mean ± SE and analysed using a two-sample t-test and two-tailed distributions. A p < 0.05 was considered statistically significant. The peptidomimetic RK-758 had anti-Acanthamoeba activity against both trophozoites and cysts in a dose-dependent manner. The RK-758 had amoebicidal and growth inhibitory activities of ≥50% at a concentration between 125 µM and 15.6 µM against the trophozoites of both Acanthamoeba strains. Inhibitory effects on the cyst formation and trophozoite re-emergence from cysts were noted at similar concentrations. Chlorhexidine had 50% activity at 7.81 µM and above against the trophozoites and cysts of both strains. In the haemolysis assay, the RK-758 lysed horse RBCs at concentrations greater than 50 µM whereas lysis occurred at concentrations greater than 125 µM for the chlorhexidine. The peptidomimetic RK-758, therefore, has activity against both the trophozoite and cyst forms of Acanthamoeba and has the potential to be further developed as an anti-microbial agent against Acanthamoeba. RK-758 may also have use as an anti-amoebic disinfectant in contact lens solutions. [ABSTRACT FROM AUTHOR]

Acanthamoeba is a free-living protozoan known to cause keratitis most commonly, especially among contact lens wearers. Treatment of Acanthamoeba keratitis is challenging as Acanthamoeba can encyst from the active form, a trophozoite, into a hibernating cyst that is refractory to antibiotics and difficult to kill; therefore, there is a need for more effective anti-amoebic strategies. In this study, we have evaluated the anti-amoebic activity of the antimicrobial peptide mimic RK-758 against Acanthamoeba castellanii. RK-758 peptidomimetic was subjected to biological assays to investigate its amoebicidal, amoebistatic, anti-encystation, and anti-excystation effects on A. castellanii. The anti-amoebic activity of the peptide mimic RK-758 was compared with chlorhexidine against the Acanthamoeba castellanii ATCC30868 and Acanthamoeba castellanii 044 (a clinical strain) with the concentrations of both ranging from 125 µM down to 7.81 µM. All experiments were performed in duplicate with three independent replicates. The data were represented as mean ± SE and analysed using a two-sample t-test and two-tailed distributions. A p < 0.05 was considered statistically significant. The peptidomimetic RK-758 had anti-Acanthamoeba activity against both trophozoites and cysts in a dose-dependent manner. The RK-758 had amoebicidal and growth inhibitory activities of ≥50% at a concentration between 125 µM and 15.6 µM against the trophozoites of both Acanthamoeba strains. Inhibitory effects on the cyst formation and trophozoite re-emergence from cysts were noted at similar concentrations. Chlorhexidine had 50% activity at 7.81 µM and above against the trophozoites and cysts of both strains. In the haemolysis assay, the RK-758 lysed horse RBCs at concentrations greater than 50 µM whereas lysis occurred at concentrations greater than 125 µM for the chlorhexidine. The peptidomimetic RK-758, therefore, has activity against both the trophozoite and cyst forms of Acanthamoeba and has the potential to be further developed as an anti-microbial agent against Acanthamoeba. RK-758 may also have use as an anti-amoebic disinfectant in contact lens solutions.

Free-living amoeba (FLA) are ubiquitously distributed in the environment. However, they are also the causative agents of opportunistic infections in humans and other animals. A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. Moreover, FLA have been detected in various biofilms around the world. Therefore, the present study aimed to check for presence of FLA in samples from household biofilms in Iran and to characterize them at the molecular level. A total of 69 biofilm samples collected from showerheads, kitchen areas, and bathroom sinks were analyzed. Positive samples for FLA were characterized at the morphological and molecular levels. Furthermore, the results of morphology analysis indicated that 26.08% (18/69) of biofilm samples were positive for Acanthamoeba spp., Vermamoeba genus, and Vahlkampfiids. According to sequence analysis, five strains of Acanthamoeba isolates related to the T4 genotype and two strains belonged to the T2 genotype. In addition, the pathogenic potential of Acanthamoeba-positive isolates was conducted using the tolerance ability test. The results of BLASTn of Vermamoeba sequences were similar to what was expected for Vermamoeba vermiformis. The above-mentioned reasons revealed that the relative high contamination of household biofilm samples with FLA may pose a risk for people using soft contact lenses and for patients with traumatic cataract. Our finding proposes that filtration should be performed in shower heads and indicates the need to monitor people at increased risk of Acanthamoeba keratitis.

Free-living amoeba (FLA) are ubiquitously distributed in the environment. However, they are also the causative agents of opportunistic infections in humans and other animals. A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. Moreover, FLA have been detected in various biofilms around the world. Therefore, the present study aimed to check for presence of FLA in samples from household biofilms in Iran and to characterize them at the molecular level. A total of 69 biofilm samples collected from showerheads, kitchen areas, and bathroom sinks were analyzed. Positive samples for FLA were characterized at the morphological and molecular levels. Furthermore, the results of morphology analysis indicated that 26.08% (18/69) of biofilm samples were positive for Acanthamoeba spp., Vermamoeba genus, and Vahlkampfiids. According to sequence analysis, five strains of Acanthamoeba isolates related to the T4 genotype and two strains belonged to the T2 genotype. In addition, the pathogenic potential of Acanthamoeba-positive isolates was conducted using the tolerance ability test. The results of BLASTn of Vermamoeba sequences were similar to what was expected for Vermamoeba vermiformis. The above-mentioned reasons revealed that the relative high contamination of household biofilm samples with FLA may pose a risk for people using soft contact lenses and for patients with traumatic cataract. Our finding proposes that filtration should be performed in shower heads and indicates the need to monitor people at increased risk of Acanthamoeba keratitis. [ABSTRACT FROM AUTHOR]