Acanthamoeba - Clinical Manifestations, Lab diagnosis, Treatment

Clinical Manifestations of Acanthamoeba

As most Granulomatous amebic encephalitis (GAE) is fatal, the prognosis for Acanthamoeba is very poor. One of the complications may include cardiopulmonary arrest.

Granulomatous amebic encephalitis (GAE)

• rare and chronic infection of the central nervous system

• usually, infection is seen in immunocompromised individuals (AIDS, undergoing immunosuppressive therapy) or people who are malnourished, chronically ill, or debilitated

• clinical symptoms for Acanthamoeba include low-grade fever, stiff neck, headache, and changes in mental status

• neurologic symptoms are focal seizures, cranial nerve palsies, hemiparesis, aphasias, ataxias, or photophobia

• as the disease progress from one week to several weeks, the patient may go into a coma

• death may result from bronchopneumonia, kidney, and liver failures.

Acanthamoeba keratitis

• it is a chronic, progressive, ulcerative infection of the eye that shows characteristic annular infiltration and congested conjunctiva

• occurs in healthy individuals who commonly use contact lenses or have undergone recent trauma to the cornea

• infection initiates with exposure to water contaminated with Acanthamoeba cysts or trophozoites

• if not treated, the infection will progress to corneal perforation, blindness, and ultimately loss of the eye

Cutaneous lesions

• it is common in disseminated cases of Acanthamoeba infections

• appear after primary inoculation

• lesions occur on the face, trunk, and extremities and start with erythematous nodules and indurated papules which suppurate and form ulcers. The nodules and papules are 1.5 cm to 3 cm in diameter while the ulcers are much larger

Laboratory diagnosis of Acanthamoeba

Since GAE is rarely diagnosed before death, Acanthamoeba diagnosis occurs post-mortem or shortly before death.

Sample

The samples collected for Acanthamoeba

• brain biopsy

• corneal lesion scrappings

• CSF

Microscopy

• demonstration of Acanthamoeba cysts and trophozoites in brain biopsy, CSF confirms GAE (75% of cases)

• Acanthamoeba keratitis is confirmed by observation of morphological forms of the parasite in the corneal lesion during wet mount microscopy.

• Acridine orange, Giemsa, LPCB, and Parker ink KOH stains are used to stain cysts and trophozoites

• other methods to visualize cysts and trophozoites include immunofluorescence by fluorescence-conjugated lectins (concanavalin A) and wheat germ agglutin

Culture

Acanthamoeba culture can be done in

• Non-nutrient agar inoculated with Page’s solution containing monoxenic culture of bacteria such as Enterobacter species, Aebacter aerogenes, and Escherichia coli

• Axenic culture – enriched broth without added bacteria

• monolayer cell lines cultures such as Hela cells, MRChuan embryonic lung cells, and monkey kidney cells

• grows best at 25° C - 30° C

Serodiagnosis

The serodiagnostic approach for Acanthamoeba is not usually taken due to less sensitivity and specificity

Imaging Methods

A CT scan for Acanthamoeba may present multiple lucent, non-enhancing lesions in the infected brain cortex while focal lesions are seen throughout the CNS

Treatment of Acanthamoeba

• not an effective treatment for GAE but Acanthomeoba keratitis has been successfully treated

• for other forms of the disease, sulphonamides, clotrimazole, and polymyxin B can be used

• other medications include topical miconazole, diamines such as propioaminide, dibromonpho amidine and antibiotics