Acanthamoeba Keratitis in Non-Contact Lens User

Abstract

Acanthamoeba is a genus of free-living amoebae. It is capable of causing serious infection, as opportunist of the central nervous systems and of the eye. Acanthamoeba keratitis is frequently associated with contact lens use. We report a case of this condition in a non-contact lens wearer. A young adult presented with severe pain and haziness of vision in the right eye. The diagnosis of Acanthamoeba keratitis was made on microscopy and culture. The patient responded clinically to treatment.

Full text

Bombay Hospital Journal, Vol. 53, No. 4, 2011
Abstract
Acanthamoeba is a genus of free-living amoebae. It is capable of causing serious
infection, as opportunists of the central nervous system and of the eye.
Acanthamoeba keratitis is frequently associated with contact lens use. We report a
case of this condition in a non-contact lens wearer. A young adult presented with
severe pain and haziness of vision in the right eye. The diagnosis of Acanthamoeba
keratitis was made on microscopy and culture. The patient responded clinically to
treatment .
*Assoc. Professor, ** Pr of es sor and HOD,
***Professor, ****Lecturer, Dept. of Microbiology,
Padm. Dr. D. Y. Patil Medical College, Pune.
Nageswari R. Gandham*, Rabindra Nath Misra**, Gurbux B. Matnani***,
Varsha D. Shahane*, Savita V. Jadhav****, Mahadev T. Juagare****
Acanthamoeba Keratitis in Non-Contact Lens User
Introduction
he genus Acanthamoeba are free-
Tli v i n g amo e b a e be l o n g in g t o
Superclass- Rhizopoda, Sub. Phylum -
Sarcodina, Phylum - Sarcomastigophora.
They are widely distributed in the soil and
water habitats throughout the world
Under unknown conditions they become
opportunistic pathogens in human beings.
They exist in trophozoite and cyst
stages. The trophozoite of Acanthamoeba
moves slowly and is identified by distinct
tapering, spine-like pseudopodia called as
acanthopodia ( acanth - meaning spine)
The cyst is 15-20 micrometer in diameter,
polygonal or star shaped with a centrally
located nucleus and a prominent
nucleolus.
Acanthamoeba causes two distinct
clinical entities- Granulomatous Amoebic
Encephalitis and Acanthamoeba keratitis.
Here we report a case of Acanthamoeba
keratitis in a non- contact lens wearer.
Case Report
A 28 year old male, was admitted to
ophthalmology ward in Pad. Dr.D.Y. Patil Medical
College and Hospital with severe, distressing pain,
redness, and watering of right eye since 45 days,
alongwith foreign body sensation in the right eye.
On examination the vision was hazy with
circum corneal congestion and lid oedema. Corneal
examination revealed complete annular peripheral
vascularisation of cornea. A circular central ulcer
was seen. Iritis was present. Pupil was dilated and
normally reacting to light. Intraocular tension was
normal. Extra ocular movements were painless. Left
eye examination was within normal limits.
The patient gave no history of trauma to the right
eye, no history of swimming or contact lens use.
Considering the chronicity, corneal scraping was
sent to the laboratory.
The Gram stain revealed no organisms. In KOH
and saline mounts fungal elements were not
detected. However double walled, polygonal cysts,
likely to be of Acanthamoeba were seen.
A presumptive diagnosis of Acanthamoeba
keratitis was made. Cultures were set up for routine
bacterial and for fungal isolation. A non-nutrient
agar (water Agar medium ) seeded with Escherichia
coli was inoculated and incubated at room
3,4
temperature.
Bacterial culture and subsequently fungal
cultures showed no growth. The water agar medium
showed characteristic clear zones where Escherichia
coli were engulfed, leaving trails of clearing after 24
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766 Bombay Hospital Journal, Vol. 53, No. 4, 2011
Fig-1 Shows culture plate with areas of
clearing where Acanthamoeba grew.
hours.
Methylene Blue stain revealed trophozoite and
cyst forms with crenated margins.
The patient was started on atropine , neosporin
and PHMB eye drops.
Discussion
O c u l a r i n f e c t i o n s d u e t o
Acanthamoeba are characterised by
chronic progressive ulcerative keratitis, in
apparently healthy individuals. Both cysts
and trophozoites are infective stages.
Swimming in contaminated water or
using contaminated solutions to clean
contact lenses may lead to this. Contact
lens usage is the single most important
risk factor and is associated with 75-93%
cases of Acanthamoeba keratitis in
5
various studies.
In developing countries, major risk
factors differ from those in developed
countries. The factors identified are, dust
particles, trauma due to vegetative matter,
bathing and fac e w a s h i n g w i t h
contaminated water. This is increasingly
being reported among non-contact lens
wearer. Males between 31- 50 years of age
are more affected than females. This is
usually the working group and most of
them are workers exposed to wet soil and
4,5,6
stick injuries.
On direct entry, amoebae become
established as conjunctival flora and
active trophozoites invade the corneal
stroma over a period of weeks to months.
The pathogenesis involves parasite-
mediated cytolysis and phagocytosis of
7
corneal epithelial cells.
Indian studies show that prevalence
rate varies from 1-3% among culture
3,5
positive corneal ulcers. Among the other
causes of infective keratitis, bacteria
(including nocardia sp) account for 33% ,
fungi for 34% , mixed infections for 2% and
2,3,5
29% of the cultures are sterile.
Though 'contact lens use' is an
important risk factor for developing
Acanthamoeba keratitis, there is an
increasing prevalence of this condition
among non-contact lens users in
4,6
developing countries. Further the latter
group has been associated with a worse
outcome than the former group. This is
attributed to initial mis-diagnosis as
herpetic, bacterial or fungal keratitis,
resulting in delay to definitive treatment in
8
this group. Therefore Acanthamoeba
keratitis should be ruled out in all cases of
infective keratitis. Cultures for the same
can be set up with ease in any diagnostic
laboratory.
In conclusion any patients suspected
of microbial keratitis, unresponsive to
Fig- 2 Methylene blue wet mount
showing cysts with crenated margins

767Bombay Hospital Journal, Vol. 53, No. 4, 2011
antibacterial and antifungal agents should
be investigated for Acanthamoeba. Better
still an in d e x o f s u s p i c i on for
Acanthamoeba should be present in all
cases of infective keratitis.
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High-concentration oxygen therapy in COPD
To add to the evidence, the first randomised trial of high-concentration versus titrated oxygen
treatment in the pre-hospital treatment of AECOPD has been published.
There is now level-1 evidence that controlled oxygen therapy titrated to achieve oxygen saturations of
88-92% substantially reduces the risk of death associated with high-concentration oxygen
treatment in AECOPD, and can now be considered the preferred therapeutic regimen, as
recommended in the British Thoracic Society guidelines. However, two major obstacles to the
implementation of this regimen exist.
However, in patients with chronic respiratory failure, a bronchodilator nebulisation driven by oxygen
might result in a rise in PaCO during the period of nebulisation. In a prolonged ambulance transfer,
2
with repeated administration of nebulised bronchodilator, this might essentially result in
continuous high-concentration oxygen therapy being delivered.
The jury is in-the routine use of high concentration oxygen therapy in AECOPD is contraindicated.
The preferred initial regimen is to titrate oxygen treatment to achieve an oxygen saturation of 88-
92%, thereby avoiding the risks of both hypoxaemia and hyperoxaemis.
Richard Beasley, Mitesh Patel, Kyle Perrin, B ronan O'Driscoll, The Lancet, 2011; 969-967378;