Microbiology of the GITMicrobiology of the GIT

Ziad Elnasser, MD, Ph.DZiad Elnasser, MD, Ph.D

AmebiasisAmebiasis

Entamoeba histolyticaEntamoeba histolytica..Acute and chronic diarrheas.Acute and chronic diarrheas.Historical background.Historical background.Pathogenic vs nonpathogenic amebas, Pathogenic vs nonpathogenic amebas,

adherence lectins, cystine proteases.adherence lectins, cystine proteases.Enzymes analysis.Enzymes analysis.Ulcerative inflammatory lesions.Ulcerative inflammatory lesions.Extraintestinal sites. Extraintestinal sites.

Entamoeba histolyticaEntamoeba histolytica

Rhizopoda.Rhizopoda.Many spps. bases of.Many spps. bases of.Glucose phosphate isomerase, Glucose phosphate isomerase,

phosphoglucomutase, oxidoreductases phosphoglucomutase, oxidoreductases (zymodemes).(zymodemes).

10 – 60 mum, nucleus, cytoplasm, cysts 10 – 60 mum, nucleus, cytoplasm, cysts and chromatoid bodies, glycogen.and chromatoid bodies, glycogen.

Life cycle and EpidemiologyLife cycle and Epidemiology Cyst, exystation in small bowel, trophozoites in Cyst, exystation in small bowel, trophozoites in

large bowel, cysts.large bowel, cysts. Fecal contamination of water, vegetables and Fecal contamination of water, vegetables and

fruits.fruits. 10% of the world population are infected each 10% of the world population are infected each

year.year. Cultural habits, sanitation, crowding, Cultural habits, sanitation, crowding,

socioeconomical status.socioeconomical status. Asymptomatic state.Asymptomatic state. Male homosexuals, amebas carry HIV virus, Male homosexuals, amebas carry HIV virus,

children and nutrition.children and nutrition.

Pathology and pathogenesisPathology and pathogenesis Lytic effect on tissues.Lytic effect on tissues. Amorphus, granular, eosinophilic material Amorphus, granular, eosinophilic material

surrounds trophozoites in tissues including surrounds trophozoites in tissues including neutrophiles → release toxic products → tissue neutrophiles → release toxic products → tissue distruction, overall protective role.distruction, overall protective role.

Spectrum of colonic lesions ranges from non Spectrum of colonic lesions ranges from non specific lesions to flask ulcers.specific lesions to flask ulcers.

Liver necrotic abscesses, periportal fibrosis.Liver necrotic abscesses, periportal fibrosis. Adherence (lectin – mucin) → proteolytic effect Adherence (lectin – mucin) → proteolytic effect

→ resistance to host effector mechanisms (C5b-→ resistance to host effector mechanisms (C5b-9).9).

Host immunityHost immunity

Immunity to recurrence.Immunity to recurrence.High antibody titer following amebic liver High antibody titer following amebic liver

abscess.abscess.Comlement resistence.Comlement resistence.sIgA protective effect, CMI and lectin Ag, sIgA protective effect, CMI and lectin Ag,

role of corticosteroids.role of corticosteroids.Vaccine strategies.Vaccine strategies.Role of mucin in protection.Role of mucin in protection.

Clinical ManifestationsClinical Manifestations Non invasive manifestation vs invasive.Non invasive manifestation vs invasive. Abdominal pain, tenderness, bloody stoolsAbdominal pain, tenderness, bloody stools Fever only in one third.Fever only in one third. Liver is enlarged if infected.Liver is enlarged if infected. All pts have heme positive stools, some as rectal All pts have heme positive stools, some as rectal

bleeding without diarrhea.bleeding without diarrhea. Fecal leukocytes might not be present.Fecal leukocytes might not be present. Fulminant colitis might need colectomy.Fulminant colitis might need colectomy. Intestinal perforation, toxic megacolon, Intestinal perforation, toxic megacolon,

ameboma.ameboma.

DiagnosisDiagnosis

Finding trophozoite or cysts in stool.Finding trophozoite or cysts in stool.Direct mount smear from the endoscope, if Direct mount smear from the endoscope, if

stool examination is negative.stool examination is negative.Differential diagnosis.Differential diagnosis. Imaging tech for liver abscess.Imaging tech for liver abscess.Serology, Abs or Ags.Serology, Abs or Ags.Aspiration of liver abscess, treatment, and Aspiration of liver abscess, treatment, and

diagnostic.diagnostic.

TreatmentTreatment

Problems with therapy.Problems with therapy. Asymptomatic cases do we treat.Asymptomatic cases do we treat. Ag and Ab detection can differentiate between Ag and Ab detection can differentiate between

E. disparE. dispar from from E. hisolyticaE. hisolytica.. Stool analysis follow up is important to follow Stool analysis follow up is important to follow

treatment.treatment. Diloxanide furoate, paromomycin, tetracycline, Diloxanide furoate, paromomycin, tetracycline,

Metronidazole, Tinidazole. Dehydroemetine.Metronidazole, Tinidazole. Dehydroemetine. Abscess drainage. Surgery ?Abscess drainage. Surgery ?

preventionprevention

Food and water fecal contamination.Food and water fecal contamination.Vegetables (lettuce), water and chlorine.Vegetables (lettuce), water and chlorine.Strong detergent soap, soak with acid.Strong detergent soap, soak with acid.Only boiling of water is effective.Only boiling of water is effective.Proper waste disposal and water Proper waste disposal and water

purification.purification.Sexual practices.Sexual practices.

Giardia lambliaGiardia lamblia

Flagellated enteric protozoan.Flagellated enteric protozoan.Endemic and epidemic diarrhea.Endemic and epidemic diarrhea.Zoomastigophora class, trophozoite, cyst.Zoomastigophora class, trophozoite, cyst.G. lamblia, intestinalis, duodenalis.G. lamblia, intestinalis, duodenalis.Antigenic variation.Antigenic variation.Culture in presence of biliary lipids, mucusCulture in presence of biliary lipids, mucus