Page 1 of 1: Acanthamoeba keratitis

2shar · Credits: 7830 My Scrapbook

Which of the following statement is TRUE regarding Acanthamoeba keratitis?

1. For isolation of the causative organism,corneal scraping should be cultured on a nutrient agar.

2. The causative agent,is a helminth whose normal habitat is soil.

3. Keratitis due to acanthamoeba is not seen in immunocmpromised host.

4. Acanthamoeba does not depend upon human host for completion of its life cycle.

i think ans is 4

BRAVO · Credits: 46105 My Scrapbook

yup it is 4 indeed!!!

sajjanshenoy · Credits: 4274 My Scrapbook

But Keratitis due to acanthamoeba may be seen in immunocompetent persons also. Its seen in people who use Soft Contact lenses. ( Parsons )

parin · Credits: 14680 My Scrapbook My Reading List 1 Books

It is a free lying amoeba found in soil, fresh water, soil water, sea water, sewage & air.

Mode of infection: Direct corneal contact with any material/water contaminated with the organism, soft contact lens wearers using home-made saline being the commonest cause.. Also mild trauma associated with contramination & also swimming or bathing in contaminated water..

C/F:

very severe pain, out of proportion to the degree of ocular inflammation d/t deep linear stromal infiltrates along corneal nerves..
watering, blepharospasm, photophobia, blurred vision...

O/E
Initially coarse opaque streaks, fine epithelial & subepithelial opacities..
Central or paracentral ring-shaped lesion with stromal infiltratesd & overlying epithelial defect in advanced cases..
Radial keratoneuritis, stromal opacities extending inwards from limbus in radial manner long corneal nerves- perineural infiltrates..

Diffuse or noduilar scleritis is also a frequent finding..
Diagnosis:

a) KOH mount- shows acanthamoeba cysts.
b) Calcofluor white stain- bright apple green cysts of acanthamoeba under fluorescence microscope
c) Lactophenol cotton blue stained film
d) Gram stain, Giemsa stain & Gomeri's silver stain are also useful..
e) Culture on non-nutrient agar (E. coli enriched) shows trophozoites within 48 hours, which gradually turn into cysts.
For culture, swabbing of conjunctiva, scrape of corneal infiltrates, contact lens & lens solution are useful...
f) Immunofluorescent Antibody techniques are also used..

Negative cultures for bacteria, fungi & viruses, together with lack of response to conventional antimicrobial therapy are clues to diagnosis..

Treatment:

Apart from cycloplegics, NSAIDs & vitamins...

1% propamidine isethionate drops
Neomycin drops
0.01-0.02% Polyhexamethylene biguanide(PHMB) solution 1 hourly
Paromomycin
Topical & oral fluconazole, itraconazole & miconazole.

Penetrating keratoplasty in non-responsive cases..

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