Microbiology of the GIT Ziad Elnasser, MD, Ph.D

Amebiasis Entamoeba histolytica. Entamoeba histolytica. Acute and chronic diarrheas. Acute and chronic diarrheas. Historical background. Historical background. Pathogenic vs nonpathogenic amebas, adherence lectins, cystine proteases. Pathogenic vs nonpathogenic amebas, adherence lectins, cystine proteases. Enzymes analysis. Enzymes analysis. Ulcerative inflammatory lesions. Ulcerative inflammatory lesions. Extraintestinal sites. Extraintestinal sites.

Entamoeba histolytica Rhizopoda. Rhizopoda. Many spps. bases of. Many spps. bases of. Glucose phosphate isomerase, phosphoglucomutase, oxidoreductases (zymodemes). Glucose phosphate isomerase, phosphoglucomutase, oxidoreductases (zymodemes). 10 – 60 mum, nucleus, cytoplasm, cysts and chromatoid bodies, glycogen. 10 – 60 mum, nucleus, cytoplasm, cysts and chromatoid bodies, glycogen.

Life cycle and Epidemiology Cyst, exystation in small bowel, trophozoites in large bowel, cysts. Cyst, exystation in small bowel, trophozoites in large bowel, cysts. Fecal contamination of water, vegetables and fruits. Fecal contamination of water, vegetables and fruits. 10% of the world population are infected each year. 10% of the world population are infected each year. Cultural habits, sanitation, crowding, socioeconomical status. Cultural habits, sanitation, crowding, socioeconomical status. Asymptomatic state. Asymptomatic state. Male homosexuals, amebas carry HIV virus, children and nutrition. Male homosexuals, amebas carry HIV virus, children and nutrition.

Pathology and pathogenesis Lytic effect on tissues. Lytic effect on tissues. Amorphus, granular, eosinophilic material surrounds trophozoites in tissues including neutrophiles → release toxic products → tissue distruction, overall protective role. Amorphus, granular, eosinophilic material surrounds trophozoites in tissues including neutrophiles → release toxic products → tissue distruction, overall protective role. Spectrum of colonic lesions ranges from non specific lesions to flask ulcers. Spectrum of colonic lesions ranges from non specific lesions to flask ulcers. Liver necrotic abscesses, periportal fibrosis. Liver necrotic abscesses, periportal fibrosis. Adherence (lectin – mucin) → proteolytic effect → resistance to host effector mechanisms (C5b- 9). Adherence (lectin – mucin) → proteolytic effect → resistance to host effector mechanisms (C5b- 9).

Host immunity Immunity to recurrence. Immunity to recurrence. High antibody titer following amebic liver abscess. High antibody titer following amebic liver abscess. Comlement resistence. Comlement resistence. sIgA protective effect, CMI and lectin Ag, role of corticosteroids. sIgA protective effect, CMI and lectin Ag, role of corticosteroids. Vaccine strategies. Vaccine strategies. Role of mucin in protection. Role of mucin in protection.

Clinical Manifestations Non invasive manifestation vs invasive. Non invasive manifestation vs invasive. Abdominal pain, tenderness, bloody stools Abdominal 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 bleeding without diarrhea. All pts have heme positive stools, some as rectal 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, ameboma. Intestinal perforation, toxic megacolon, ameboma.

Diagnosis Finding trophozoite or cysts in stool. Finding trophozoite or cysts in stool. Direct mount smear from the endoscope, if stool examination is negative. Direct mount smear from the endoscope, if 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 diagnostic. Aspiration of liver abscess, treatment, and diagnostic.

Treatment Problems with therapy. Problems with therapy. Asymptomatic cases do we treat. Asymptomatic cases do we treat. Ag and Ab detection can differentiate between E. dispar from E. hisolytica. Ag and Ab detection can differentiate between E. dispar from E. hisolytica. Stool analysis follow up is important to follow treatment. Stool analysis follow up is important to follow treatment. Diloxanide furoate, paromomycin, tetracycline, Metronidazole, Tinidazole. Dehydroemetine. Diloxanide furoate, paromomycin, tetracycline, Metronidazole, Tinidazole. Dehydroemetine. Abscess drainage. Surgery ? Abscess drainage. Surgery ?

prevention 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 purification. Proper waste disposal and water purification. Sexual practices. Sexual practices.

Giardia 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, mucus Culture in presence of biliary lipids, mucus