Free-living Amoeba

1. ACANTHAMOEBA
FREE LIVING AMOEBA

2. FREE-LIVING AMOEBA
Amphizoic amoebae
- They have also been
called amphizoic amoebae
because these amoebae
have the ability to exist as
free-living organisms in
nature and only occasionally
invade a host and live as
parasites within host tissue.

3. ACANTHAMOEBA
A microscopic, free-living amoeba that can cause rare,
but severe infections of the eye, skin, and central
nervous system.
Several species of Acanthamoeba, including A.
culbertsoni, A. polyphaga, A. castellanii, A. astronyxis,
A. hatchetti, A. rhysodes, A. divionensis, A. lugdunensis,
and A. lenticulata are implicated in human disease.
 The important species is A.culbertsoni

4. ACANTHAMOEBA
Acanthamoeba spp. have been found in:
• soil • heating, ventilating, and
• fresh, brackish, and sea air conditioning systems
water • mammalian cell cultures
• Sewage • Vegetables
• swimming pools • human nostrils and
• contact lens equipment; throats
• medicinal pools • human and animal brain,
• dental treatment units skin, and lung tissues.
• dialysis machines

5. ACANTHAMOEBA
Has two stages, cysts and trophozoites, in its life
cycle. No flagellated stage exists as part of the life
cycle.
The trophozoites replicate by mitosis.
 When Acanthamoeba spp. enters the eye it can
cause severe keratitis in otherwise healthy
individuals, particularly contact lens users .
 When it enters the respiratory system or through
the skin, it can invade the central nervous system
by hematogenous dissemination causing
granulomatous amebic encephalitis (GAE) or
disseminated disease, or skin lesions in
individuals with compromised immune systems

6. ACANTHAMOEBA
LIFE CYCLE STAGES
Free-living trophozoites and cysts occur in both
the soil and freshwater.

7. ACANTHAMOEBA
Life cycle:

8. ACANTHAMOEBA
There are two morphological forms:
 Trophozoite
- A trophozoite is 20-50µm in size
- Rough exterior with several spine like
projections(acanthopoda).
 Cyst
- Spherical and 15µm in diameter.
Both forms can be the source of infection

9. ACANTHAMOEBA
Trophozoite Cyst
 Feeding & dividing  Response to adversity
 Asexual  Dormant, resistant
 Cyst forming  Double-walled with pores

10. ACANTHAMOEBA
Pathogenicity and Clinical Features:
 Granulomatous Amebic Encephalitis (GAE) and
disseminated infection primarily affect people with
compromised immune systems.
 Commonly seen in immunocompromised patients,
including those with neoplasia, systemic lupus
erythematosus, human immunodeficiency virus
and tuberculosis
Incubation period:
 Unknown but estimated at weeks to months. The
route of infection is aerosol or direct inoculation
with hematogenous spread to the CNS.

11. ACANTHAMOEBA
Risk Factors: Symptoms:
• Alcoholism • Headache
• Drug abuse • Confusion
• Chemotherapy • fever,
• Corticosteroids • Lethargy
• Organ transplantation • Nausea and vomiting
• Seizures
Signs: • Photophobia
• Neck stiffness • Neck stiffness.
• Focal neurological deficits • Patients may become
• Patients may also develop frankly psychotic.
raised intracranial pressure

12. Acanthamoeba Keratitis
 A progressive disease of the cornea, which
is sight-threatening
 Commonly seen in:
- immunocompetent patients.
- However, infection does not
confer immunity and reinfection is
common.
 Risk factors:
• poor contact lens hygiene
• corneal abrasion
• exposure of the eye to contaminated water

13. Acanthamoeba Keratitis
 Affected individual  Signs:
may complain of: • Conjunctival hyperemia
• Eye pain • Episcleritis
• Eye redness • Scleritis
• Blurred vision • Loosening of the corneal
• Sensitivity to light epithelium.
(photophobia) • Rarely, trophozoites can
• Sensation of something
infiltrate the corneal
in the eye
nerve and retina, leading
• Excessive tearing
to chorioretinitis

14. Acanthamoeba Keratitis
Diagnosis
 CSF wet mount
-usually lymphocyte
predominance and low
glucose (motile trophozoites)
 Culture-Agar plates seeded with
E.coli
 Immunofluorescence or
polymerase chain reaction (PCR)
 Corneal scrape or biopsy

15. Acanthamoeba Keratitis
Prevention and Control
These guidelines should be followed by all contact lens users to help
reduce the risk of eye infections:
 Visit your eye care provider for regular eye
examinations.
 Wear and replace contact lenses according to the
schedule prescribed by your eye care provider.
 Remove contact lenses before any activity involving
contact with water, including showering, using a hot
tub, or swimming.
 Wash hands with soap and water and dry before
handling contact lenses.

16. Acanthamoeba Keratitis
Prevention and Control
 Clean contact lenses according to instructions from your
eye care provider and the manufacturer's guidelines.
1. Never reuse or top off old solution. Use fresh cleaning or
disinfecting solution each time lenses are cleaned and stored.
2. Never use saline solution or rewetting drops to disinfect lenses.
Neither solution is an effective or approved disinfectant.
3. Be sure to clean, rub, and rinse your lenses each time you
remove your lenses. Rubbing and rinsing your contact lenses will
aid in removing harmful microbes and residues.

17. Acanthamoeba Keratitis
Prevention and Control
 Store reusable lenses in the proper storage case.
1. Storage cases should be rubbed and rinsed with sterile contact
lens solution (never use tap water), emptied, and left open to
dry after each use.
2. Replace storage cases at least once every three months.
 Contact lens users with questions regarding which
solutions are best for them should consult their eye care
providers. They should also consult their eye care
providers if they have any of the following symptoms: eye
pain or redness, blurred vision, sensitivity to light,
sensation of something in the eye, or excessive tearing.

18. Granulomatous Amebic Encephalitis
 A serious
infection of the
brain and spinal
cord that typically
occurs in persons
with a
compromised
immune system.

19. Granulomatous Amebic Encephalitis
Symptoms include:
• Mental status changes body
• Loss of coordination • Double vision
• Fever • Sensitivity to light
• Muscular weakness or • Other neurologic
partial paralysis problems
affecting one side of the

20. ACANTHAMOEBA
Treatment:
 Granulomatous Amebic Encephalitis (GAE) is treated
with pentamidine, usually in combination with one or
more of the following:
• Ketoconazole
• Hydroxystilbamidine
• Paromomycin
• 5-fluorocytosine polymyxin
• Sulfadiazine
• Trimethoprim-sulfamethoxazole
• Azithromycin

21. ACANTHAMOEBA
Treatment:
 Acanthamoeba keratitis
- Therapy should include the cationic antiseptic
agents, of which chlorhexidine or
polyhexamethylene biguanide (PHMB) is the most
effective.
 Ocular lesions
- Enucleation of ulcer and corneal transplant

22. REFERENCES
• Contact Lens News and Information. (2012, February 20). Contact Lens Solutions Ineffective
Against Acanthamoeba, Study Finds. Retrieved August 10, 2012, from
http://t3.gstatic.com/images?q=tbn:ANd9GcTB4chV7tr0UeG44UKnU9qSBv4IOy_0_vA
JrnYHIvhM75iGwMF
• Centers for Disease Control and Prevention (CDC). Acanthamoeba - Granulomatous Amebic
Encephalitis (GAE); Keratitis. Retrieved August 11, 2012, from
http://www.cdc.gov/parasites/acanthamoeba/disease.html
• Centers for Disease Control and Prevention (CDC). Laboratory Identification of Parasites of
Public Health Concern; Free-Living Amebic Infections. Retrieved August 11, 2012, from
http://www.dpd.cdc.gov/dpdx/HTML/FreeLivingAmebic.htm
• Simon Kilvington, PhD. (2008). Physiological Response of Acanthamoeba to
Contact Lens Disinfectants [Powerpoint Format]. Retrieved August 11, 2012, from
http://www.google.com.ph/url?sa=t&rct=j&q=physiological%20response%20of%20ac
• Animal Planet. Monsters inside me. Acanthamoeba picture. Retrieved August 15, 2012,
from http://animal.discovery.com/invertebrates/monsters-inside-me/acanthamoeba-
keratitis/

23. REFERENCES
• The University of Edinburgh. (2003, May 28). Acanthamoeba. Retrieved August 15, 2012,
from http://www.bms.ed.ac.uk/research/others/smaciver/Comp1.jpg
• Baylor College of Medicine. (2008, January, 30). Human Genome Sequencing Center; About
Acanthamoeba castellani Neff. Retrieved August 15, 2012, from
http://www.hgsc.bcm.tmc.edu/microbial-detail.xsp?project_id=163
• Naveed, Khan. (2009). Acanthamoeba Biology and Pathogenesis. Retrieved August 15,
2012, from http://www.caister.com/supplementary/acanthamoeba/c10.html

24. THANK YOU!
• Edna Mae C. Genzola, RMT
• Katherine Royce L. Panizales, RMT
• Mary Jean D. Somcio, RMT