Amebiasis summary and recommendations

阿米巴感染簡介

【腸內感染】

²  Intestinal amebiasis is caused by the protozoan Entamoeba histolytica. Amebic cysts are resistant to chlorine at the levels used in water supplies, but disinfection with iodine may be effective. The pathogenic potential of E. moshkovskii remains unclear. There are three species of intestinal amebae with identical morphologic characteristics:

Ø   E. histolytica, E. dispar, and E. moshkovskii.

u  E. histolyticaèmost symptomatic disease

u  E. dispar is nonpathogenic and does not cause clinical disease

²  Clinical amebiasis generally has a subacute onset, usually over 2-3 weeks. Symptoms:

Ø   asymptomatic, or mild diarrhea

Ø   severe dysentery(下痢) and bloody stools

Ø   producing abdominal pain,

Ø   fulminant colitis with bowel necrosisàperforation and peritonitis

Ø   toxic megacolon.

²  Diagnosis is best accomplished by the combination of serology or antigen testing together with identification of the parasite in stool or extraintestinal sites.

²  All E. histolytica infections should be treated, even in the absence of symptoms. The goals of antibiotic therapy of intestinal amebiasis are to eliminate the invading trophozoites and to eradicate intestinal carriage of the organism.

Ø   Metronidazole(500 to 750 mg TID for 7-10 days)

Ø   Tinidazole(2 g QD for 3 days).

We also suggest subsequent treatment with paromomycin to eliminate intraluminal cysts. Dosing is outlined above.

  

【腸外感染】

²  Extraintestinal manifestations of Entamoeba histolytica include amebic liver abscess and more rare manifestations such as pulmonary, cardiac, and brain involvement. Amebae establish hepatic infection by ascending the portal venous system.

²  Patients with amebic liver abscess typically present with one to two weeks of right upper quadrant pain and fever. Concurrent diarrhea is present in less than one-third of patients. Physical examination frequently reveals hepatomegaly and point tenderness over the liver.

²  The diagnosis of amebic liver abscess is generally established by radiographic imaging and confirmed with serologic or antigenic testing, perhaps supplemented with stool microscopy or antigenic testing of stool, with or without evaluation for the parasite in liver abscess fluid.

²  Needle aspiration of amebic liver abscess is not routinely required but may be warranted if:

Ø   the cyst appears to be at imminent risk of rupture (particularly for lesions in the left lobe),

Ø   there is clinical deterioration or lack of response to empiric therapy

Ø   exclusion of alternative diagnoses is needed.

²  We suggest treatment of amebic liver abscess or with

Ø   Metronidazole(500 to 750 mg TID for 7-10 days)

Ø   Tinidazole(2 g QD for 5 days)

We also suggest subsequent treatment with paromomycin to eliminate intraluminal cysts.

²  Pleural space involvement of E. histolytica can occur in the setting of liver abscess rupture into the pleural space, resulting in an amebic empyema. Rupture into the lung can lead to consolidation, abscess formation, and/or hepatobronchial fistula. Clinical manifestations include pain, cough, hemoptysis, and dyspnea. Cough may be productive of necrotic material that can include liver abscess contents. Treatment of amebic pleural effusions should consist of aspiration and antimicrobial therapy. We suggest treatment of pulmonary infection with metronidazole or tinidazole. We suggest subsequent treatment with paromomycin to eliminate intraluminal cysts.