Acanthamoeba: Difference between revisions

Latest revision as of 16:47, 25 January 2022

Background

Microbiology

One of the free-living amoebae
Seventeen genotypes (T1-T17), of which 10 have caused disease in humans
Most common is Acanthamoeba castellanii complex (T4)
Species traditionally organized morphologically into 3 groups

Group	Species	Trophozoite Size	Cyst Size
I	A. astronyxis, A. comandoni, A. tubiashi, A. byersi	30-125 μm	16-35 μm
II	A. castellanii, A. polyphaga, A. rhysodes, A. hatchetti	15-45 μm	≤18 μm
III	A. culbertsoni, A. royreba, A. lenticulata	15-45 μm	<18 μm with different morphologies

Life Cycle

Cysts and trophozoites can cause disease

Epidemiology

More common in immunocompromised patients, with risk factors including AIDS, liver disease, diabetes, organ transplantation, corticosteroid use, chemotherapy, and rituximab

Clinical Manifestations

Granulomatous amebic encephalitis

Subacute presentation of encephalitis (fever, headache, nuchal rigidity, behaviour changes, altered level of conciousness, focal neurological deficiets)
Often preceded by cutaneous lesions by months
- May include ulcers, nodules, and subcutaneous abscesses
- Amoebic granulomas on biopsy

Non-neurological disseminated acanthamoebiasis

Rarely, patients may have disseminated disease without evidence of CNS involvement
Mostly seen in patients with AIDS, transplant, or prolonged corticosteroid use
Most commonly involves skin, but can involve liver, lungs, and bones

Amoebic keratitis

Sight- and eye-threatening infection
Often secondary to corneal trauma or improper contact lens hygiene
Present with severe pain, photophobia, tearing
May see dendiform epitheliopathy or stromal ring

Diagnosis

Ameba culture on nutrient agar with layer of gram-negative bacteria at 30ºC (cornea/skin) or 37–C (brain/lung)
Species identification done with 18S rDNA sequencing

Management

Granulomatous amebic encephalitis

Can consider a combinaction of pentamidine, azoles, flucytosine, sulfadiazine, miltefosine, amikacin, and voriconazole

Amoebic keratitis

Can be treated with any of:
- PHMB
- Chlorhexadine
- Topical and oral voriconazole
- Propamidine
- Hexamidine

@@ Line 1: / Line 1: @@
 ==Background==
 ===Microbiology===
-* One of the [[free-living amoebae]]
+*One of the [[free-living amoebae]]
-* Seventeen genotypes (T1-T17), of which 10 have caused disease in humans
+*Seventeen genotypes (T1-T17), of which 10 have caused disease in humans
-* Most common is ''[[Acanthamoeba castellanii]]'' complex (T4)
+*Most common is ''[[Acanthamoeba castellanii]]'' complex (T4)
+*Species traditionally organized morphologically into 3 groups
+{| class="wikitable"
+!Group
+!Species
+!Trophozoite Size
+!Cyst Size
+|-
+|I
+|''A. astronyxis'', ''A. comandoni'', ''A. tubiashi'', ''A. byersi''
+|30-125 μm
+|16-35 μm
+|-
+|II
+|''A. castellanii'', ''A. polyphaga'', ''A. rhysodes'', ''A. hatchetti''
+|15-45 μm
+|≤18 μm
+|-
+|III
+|''A. culbertsoni'', ''A. royreba'', ''A. lenticulata''
+|15-45 μm
+|<18 μm with different morphologies
+|}
 ===Life Cycle===
-* Cysts and trophozoites can cause disease
+*Cysts and trophozoites can cause disease
 ===Epidemiology===
-* More common in immunocompromised patients, with risk factors including [[AIDS]], liver disease, diabetes, organ transplantation, corticosteroid use, chemotherapy, and rituximab
+*More common in immunocompromised patients, with risk factors including [[AIDS]], liver disease, diabetes, organ transplantation, corticosteroid use, chemotherapy, and rituximab
-==Clinical Presentation==
+==Clinical Manifestations==
 ===Granulomatous amebic encephalitis===
-* Subacute presentation of encephalitis (fever, headache, nuchal rigidity, behaviour changes, altered level of conciousness, focal neurological deficiets)
+*Subacute presentation of encephalitis (fever, headache, nuchal rigidity, behaviour changes, altered level of conciousness, focal neurological deficiets)
-* Often preceded by cutaneous lesions by months
+*Often preceded by cutaneous lesions by months
-** May include ulcers, nodules, and subcutaneous abscesses
+**May include ulcers, nodules, and subcutaneous abscesses
-** Amoebic granulomas on biopsy
+**Amoebic granulomas on biopsy
 ===Non-neurological disseminated acanthamoebiasis===
-* Rarely, patients may have disseminated disease without evidence of CNS involvement
+*Rarely, patients may have disseminated disease without evidence of CNS involvement
-* Mostly seen in patients with AIDS, transplant, or prolonged corticosteroid use
+*Mostly seen in patients with AIDS, transplant, or prolonged corticosteroid use
-* Most commonly involves skin, but can involve liver, lungs, and bones
+*Most commonly involves skin, but can involve liver, lungs, and bones
 ===Amoebic keratitis===
-* Sight- and eye-threatening infection
+*Sight- and eye-threatening infection
-* Often secondary to corneal trauma or improper contact lens hygiene
+*Often secondary to corneal trauma or improper contact lens hygiene
-* Present with severe pain, photophobia, tearing
+*Present with severe pain, photophobia, tearing
-* May see dendiform epitheliopathy or stromal ring
+*May see dendiform epitheliopathy or stromal ring
+== Diagnosis ==
+* Ameba culture on nutrient agar with layer of gram-negative bacteria at 30ºC (cornea/skin) or 37–C (brain/lung)
+* Species identification done with 18S rDNA sequencing
 ==Management==
 ===Granulomatous amebic encephalitis===
-* Can consider a combinaction of [[Is treated by::pentamidine]], [[Is treated by::azoles]], [[Is treated by::flucytosine]], [[Is treated by::sulfadiazine]], [[Is treated by::miltefosine]], [[Is treated by::amikacin]], and [[Is treated by::voriconazole]]
+*Can consider a combinaction of [[Is treated by::pentamidine]], [[Is treated by::azoles]], [[Is treated by::flucytosine]], [[Is treated by::sulfadiazine]], [[Is treated by::miltefosine]], [[Is treated by::amikacin]], and [[Is treated by::voriconazole]]
 ===Amoebic keratitis===
-* Can be treated with any of:
-** [[Is treated by::PHMB]]
-** [[Is treated by::Chlorhexadine]]
-** Topical and oral [[Is treated by::voriconazole]]
-** [[Is treated by::Propamidine]]
-** [[Is treated by::Hexamidine]]
+*Can be treated with any of:
-{{DISPLAYTITLE:''Acanthamoeba'' species}}
+**[[Is treated by::PHMB]]
+**[[Is treated by::Chlorhexadine]]
+**Topical and oral [[Is treated by::voriconazole]]
+**[[Is treated by::Propamidine]]
+**[[Is treated by::Hexamidine]]
+{{DISPLAYTITLE:''Acanthamoeba''}}
 [[Category:Protozoa]]