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 on non-nutrient agar at 37 & 43°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 AI&BI (20 & 15% respectively) than Endoxan or
Prednisolone treated and Acanthanweba infected groups A II & B 11 (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 Al & BI and less severe changes in groups All & BB, in the
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.
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