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Updated: Apr 19, 2026
Author Spotlight: Studying Behavior of Acanthamoeba to Develop Targeted Strategies for Preventing Acanthamoeba Keratitis
Published on: September 20, 2024
Pathogenic assays of acanthamoeba belonging to the t4 genotype
Hamed Mirjalali1, Maryam Niyyati2, Hoda Abedkhojasteh1
1Dept. of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Background:
Acanthamoeba genus is introduced as opportunistic and cosmopolitan parasite. Monkey and wistar rat are appropriate models for experimental study on Acanthamoeba infection. In this study Acanthamoeba spp. were isolated from hot spring (HS), windows dust (WD) and a corneal sample of keratitis patient (KP) and their pathogenicity surveyed by in vitro and in vivo tests.
Methods:
Isolates of Acanthamoeba were cultivated axenically for 12 months in PYG medium. Overall, 30 wistar rats, in 6 equal groups were used for developing experimental Acanthamoeba keratitis (AK) and Granulomatous Amoebic Encephalitis (GAE). The Keratitis and Granulomatous Encephalitis experiments were performed by intrastromal and intranasal inoculation of Acanthamoeba cysts, respectively. Pathogenicity of the three isolates was also evaluated by in vitro test using osmotolerance and temperature tolerance assays. Identification of genotypes were performed by PCR technique and sequencing.
Result:
None of the isolates could perform AK and GAE in wistar rats, although all isolates were described as T4 genotype. Isolates obtained from KP and WD could grow only in 30 °C, but not in 37 °C and 40 °C. On the other hand, HS isolate grew in 30 °C and 37 °C but not in 40 °C. Moreover, all of isolate grew in 0.5 M mannitol but not in 1 M and 1.5 M.
Conclusion:
T4 isolates with a long-term axenic culture and different factors related to host and parasite may play role in pathogenicity of these free-living amoebae.
Insights
Acanthamoeba T4 genotype isolates, despite being cultured for a year, did not cause keratitis or encephalitis in wistar rats. Their limited growth at higher temperatures and salt concentrations suggests reduced pathogenicity in vivo.
Area of Science:
- Microbiology
- Parasitology
- Infectious Diseases
Background:
- Acanthamoeba are opportunistic, cosmopolitan parasites.
- Wistar rats serve as a model for studying Acanthamoeba infections.
- Isolates were obtained from hot springs, window dust, and a keratitis patient.
Purpose of the Study:
- To isolate and characterize Acanthamoeba species from environmental and clinical sources.
- To evaluate the pathogenicity of these isolates in a wistar rat model.
- To determine the in vitro tolerance of isolates to temperature and osmotic stress.
Main Methods:
- Axenic cultivation of Acanthamoeba isolates for 12 months.
- Intrastromal and intranasal inoculation of wistar rats to induce keratitis and encephalitis.
- In vitro assessment of osmotolerance and temperature tolerance.
- Genotyping of isolates using PCR and sequencing.
Main Results:
- All isolates belonged to the T4 genotype.
- No Acanthamoeba keratitis or Granulomatous Amoebic Encephalitis was observed in wistar rats.
- Isolates showed limited growth at temperatures above 30°C and in 1M mannitol.
Conclusions:
- Long-term axenic culture may attenuate the pathogenicity of T4 Acanthamoeba isolates.
- Host and parasite factors likely influence the virulence of these free-living amoebae.
- Further research is needed to understand Acanthamoeba pathogenicity.
