PURPOSE: To produce animal models of Acanthamoeba keratitis and to evaluate the advantages and adaptation range of each of the three methods employed. MATERIALS AND METHODS: Mice and Wistar rats in three groups of 15 rats and 15 mice each were used to establish the models. Right corneas in group A were scratched and challenged with Acanthamoeba. Those in group B were scratched and covered with contact lenses incubated with Acanthamoeba. Those in group C received an intrastromal injection of Acanthamoeba. Five rats and 5 mice in each group were used for histopathological investigations and the other 10 in each group were used for clinical evaluation. The models were evaluated by slit lamp examination, microscopic examination and culture of corneal scrapings, HE staining of corneal sections, and pathological scoring of the infections. RESULTS: Four rats and 6 mice in group A, 7 rats and 8 mice in group B, and 10 rats and 10 mice in group C developed typical Acanthamoeba keratitis. CONCLUSION: Corneal scratching alone has the lowest infection rate, while scratching and then covering with contaminated contact lenses has a moderate rate of infection and most closely mimics what happens in most human infections. Intrastromal injection of Acanthamoeba gives a much higher infection rate and more severe Acanthamoeba keratitis.
Acanthamoeba/growth & development ; Acanthamoeba Keratitis/*parasitology/pathology ; Animals ; Contact Lenses/adverse effects/parasitology ; Cornea/parasitology/pathology ; Disease Models, Animal ; Female ; Male ; Mice ; Microscopy ; Rats ; Rats, Wistar

PURPOSE: This study aims to determine the frequency of opthalmyomyiasis externa and the ocular findings of disease in Southern Khorasan. METHODS: All patients referred to the emergency department of Valiaser hospital during the year 2011 with external ophthalmomyiasis were enrolled in this study. The diagnosis of external ophthalmomyiasis was made according to clinical findings and the presence of Oestrus ovis larvae. RESULTS: There were 18 cases of external ophthalmomyiasis in the emergency department of Valiaser hospital in 2011. Most cases had the common signs and symptoms of allergic conjunctivitis, except for three males who were referred with respective complaints of red eye, foreign body sensation, and swelling around the eyelids after contact injury the previous day; corneal infiltration was present in three cases. The visual acuity among the three cases that had peripheral corneal involvement was 20 / 30 in both eyes. The bulbar conjunctiva showed chemosis in all cases and a ropy pattern discharge that was clinically compatible with external ophthalmomyiasis. However, in one case, microscopic slit lamp examination did not show Oestrus ovis larvae. CONCLUSIONS: The frequency of external ophthalmomyiasis was high in this region. Although external ophthalmomyiasis usually manifests as allergic conjunctivitis, coronary-like corneal infiltration may be considered in the differential diagnosis of external ophthalmomyiasis or toxic insult.
Adolescent ; Adult ; Aged ; Aged, 80 and over ; Animals ; Cornea/parasitology/*pathology ; Diagnosis, Differential ; *Diptera ; *Emergency Service, Hospital ; Eye Infections, Parasitic/*diagnosis/epidemiology/parasitology ; Female ; Humans ; Incidence ; Iran/epidemiology ; Larva ; Male ; Middle Aged ; Myiasis/*diagnosis/epidemiology/parasitology ; Retrospective Studies ; Young Adult

The pathogenic mechanism of granulomatous amebic encephalitis (GAE) and amebic keratitis (AK) by Acanthamoeba has yet to be clarified. Protease has been recognized to play an important role in the pathogenesis of GAE and AK. In the present study, we have compared specific activity and cytopathic effects (CPE) of purified 33 kDa serine proteinases from Acanthamoeba strains with different degree of virulence (A. healyi OC-3A, A. lugdunensis KA/E2, and A. castellanii Neff). Trophozoites of the 3 strains revealed different degrees of CPE on human corneal epithelial (HCE) cells. The effect was remarkably reduced by adding phenylmethylsulfonylfluoride (PMSF), a serine proteinase inhibitor. This result indicated that PMSF-susceptible proteinase is the main component causing cytopathy to HCE cells by Acanthamoeba. The purified 33 kDa serine proteinase showed strong activity toward HCE cells and extracellular matrix proteins. The purified proteinase from OC-3A, the most virulent strain, demonstrated the highest enzyme activity compared to KA/E2, an ocular isolate, and Neff, a soil isolate. Polyclonal antibodies against the purified 33 kDa serine proteinase inhibit almost completely the proteolytic activity of culture supernatant of Acanthamoeba. In line with these results, the 33 kDa serine proteinase is suggested to play an important role in pathogenesis and to be the main component of virulence factor of Acanthamoeba.
Virulence Factors/isolation & purification/*metabolism ; Virulence ; Trophozoites/physiology ; Substrate Specificity ; Soil/parasitology ; Serine Endopeptidases/isolation & purification/*metabolism ; Humans ; Epithelial Cells/parasitology/*pathology ; Encephalitis ; Cornea/cytology/parasitology/*pathology ; Cells, Cultured ; Animals ; Acanthamoeba castellanii/enzymology/growth & development/pathogenicity ; Acanthamoeba Keratitis/parasitology ; Acanthamoeba/classification/*enzymology/growth & development/*pathogenicity