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Free-living Amoeba


  2. 2. FREE-LIVING AMOEBAAmphizoic amoebae - They have also beencalled amphizoic amoebaebecause these amoebaehave the ability to exist asfree-living organisms innature and only occasionallyinvade a host and live asparasites within host tissue.
  3. 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. 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. 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. 6. ACANTHAMOEBALIFE CYCLE STAGES Free-living trophozoites and cysts occur in both the soil and freshwater.
  7. 7. ACANTHAMOEBALife cycle:
  8. 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. 9. ACANTHAMOEBATrophozoite Cyst Feeding & dividing  Response to adversity Asexual  Dormant, resistant Cyst forming  Double-walled with pores
  10. 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. 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. 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. 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. 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. 15. Acanthamoeba KeratitisPrevention and ControlThese guidelines should be followed by all contact lens users to helpreduce 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. 16. Acanthamoeba KeratitisPrevention and Control Clean contact lenses according to instructions from your eye care provider and the manufacturers 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. 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. 18. Granulomatous Amebic Encephalitis A serious infection of the brain and spinal cord that typically occurs in persons with a compromised immune system.
  19. 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. 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. 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. 22. REFERENCES• Contact Lens News and Information. (2012, February 20). Contact Lens Solutions Ineffective Against Acanthamoeba, Study Finds. Retrieved August 10, 2012, from JrnYHIvhM75iGwMF• Centers for Disease Control and Prevention (CDC). Acanthamoeba - Granulomatous Amebic Encephalitis (GAE); Keratitis. Retrieved August 11, 2012, from• Centers for Disease Control and Prevention (CDC). Laboratory Identification of Parasites of Public Health Concern; Free-Living Amebic Infections. Retrieved August 11, 2012, from• Simon Kilvington, PhD. (2008). Physiological Response of Acanthamoeba to Contact Lens Disinfectants [Powerpoint Format]. Retrieved August 11, 2012, from• Animal Planet. Monsters inside me. Acanthamoeba picture. Retrieved August 15, 2012, from keratitis/
  23. 23. REFERENCES• The University of Edinburgh. (2003, May 28). Acanthamoeba. Retrieved August 15, 2012, from• Baylor College of Medicine. (2008, January, 30). Human Genome Sequencing Center; About Acanthamoeba castellani Neff. Retrieved August 15, 2012, from• Naveed, Khan. (2009). Acanthamoeba Biology and Pathogenesis. Retrieved August 15, 2012, from
  24. 24. THANK YOU!• Edna Mae C. Genzola, RMT• Katherine Royce L. Panizales, RMT• Mary Jean D. Somcio, RMT