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Free living amoebae as opportunistic parasites in immunocompromised hosts
A F el-Fakahany1, R R Fahmy, A S Mohamed
1Department of Parsitology, Benha Faculty of Medicine, Zagazig University, Egypt.
Abstract:
The acquisition of invasiveness of mammalian tissue by free living amoebae (FLA) is an extremely noteworthy phenomenon. Many factors may be responsible for this evolutionary change in their physiology. The present work aimed to clarify the host factors in this problem. Albino mice were the laboratory animals used in this work. Non-pathogenic strains of FLA were isolated from ear, nose and pharyngeal swabs and from contact lenses of patients attending out patient clinics in Benha University Hospitals. Isolation was done by cultivation of non-nutrient agar at 37 & 43 degrees C and identification was made by flagellation test. The degree of pathogenicity of isolated strains was assessed by using animal pathogenicity test. Endoxan (0.7 mg/kg) and Prednisolone (2 mg/kg) were used for 15 days orally to suppress the immunity of clean mice before their inoculation intranasally with the isolated strains. All groups were observed for 3 weeks post-infection. Mortality rates recorded were higher in Endoxan or Prednisolone treated and Naegleria infected groups A I & B I (20 & 15% respectively) than Endoxan or Prednisolone treated and acanthamoeba infected groups A II & B II (10%) and drug control (10%). Histopathological examination of brain and meninges revealed severe changes in form of severe meningoencephalitis, severe vacuolar degeneration, and moderate haemorrhage and necrosis in brains of groups AI & BI and less severe changes in groups AII & BII (10%) form of-non granulomatous encephalitis. Drug control groups showed negligible changes. Great attention must be paid to reveal the presence of FLA before using immunosuppressive drugs in human cases.
Insights
Free-living amoebae (FLA) can invade mammalian tissue, especially when host immunity is suppressed. This study highlights the increased pathogenicity of FLA in immunosuppressed mice, urging caution before using such drugs in humans.
Area of Science:
- Medical Microbiology
- Immunology
- Pathology
Background:
- Free-living amoebae (FLA) can acquire invasiveness, posing a potential health risk.
- Understanding host factors influencing FLA pathogenicity is crucial for disease prevention.
Purpose of the Study:
- To investigate the role of host immune status in the invasiveness of free-living amoebae.
- To assess the pathogenicity of isolated FLA strains in immunosuppressed animal models.
Main Methods:
- Isolation and identification of non-pathogenic FLA strains from clinical samples.
- Induction of immunosuppression in albino mice using Endoxan and Prednisolone.
- Intranasal inoculation of mice with FLA strains and observation of infection outcomes.
- Histopathological examination of brain and meninges for pathological changes.
Main Results:
- Higher mortality rates were observed in immunosuppressed mice infected with Naegleria and Acanthamoeba compared to controls.
- Severe meningoencephalitis, vacuolar degeneration, hemorrhage, and necrosis were noted in Naegleria-infected groups.
- Less severe non-granulomatous encephalitis was observed in Acanthamoeba-infected groups.
- Drug control groups showed negligible pathological changes.
Conclusions:
- Host immune suppression significantly enhances the pathogenicity of free-living amoebae.
- Screening for FLA presence is recommended before administering immunosuppressive therapies in humans.
- FLA infections in immunocompromised individuals warrant careful consideration and management.