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Biomedical GIT
This document summarizes various bacterial, parasitic, and viral causes of dysentery and diarrhea. It describes key characteristics of common pathogens like E. coli, Shigella, Salmonella, Campylobacter, Vibrio cholerae, Yersinia enterocolitica, Helicobacter pylori, Giardia lamblia, Entamoeba histolytica, and parasites such as Ascaris lumbricoides, hookworms, and Schistosoma. For each pathogen, it discusses microscopy appearance, culture characteristics, and clinical manifestations of resulting diseases.
Biomedical GIT
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- 2. Causes of dysenteryand/or diarrhoea Bacteria ! Diarrhoeagenic E. coli (EHEC, EIEC etc.) ! Shigella " Salmonella " Campylobacter " Yersinia enterocolitica " Vibrio cholera Parasites Viruses
- 3. Diarrhoeagenic E. coli 6types • Enterohaemorrhagic E.coli (EHEC) • Enterotoxigenic E.coli (ETEC) • Enteropathogenic E.coli (EPEC) • Enteroinvasive E.coli (EIEC) • Enteroaggregative E.coli (EAEC) • Diffusely adherent E.coli (DAEC)
- 4. E. Coli -Microscopy Appear as gram negative bacilli
- 5. E. Coli -Culture Can be grown within 24 hours Cultured on non selective media
- 6. Enterohaemorrhagic E.coli (EHEC) "Causes Heamolytic-uremic syndrome (HUS) " d/t EHEC colonizing the large intestine and subsequently releases Shiga toxins that enter the bloodstream, travels to the kidneys and causes cell damage
- 7. Shigella 4 types ! S.flexneri ( most common ) ! S. sonnei ! S . dysenteriae ( most virulent ) ! S . boydii
- 8. Shigella - Microscopy Appearas gram negative bacilli
- 9. Shigella dysenteriae " Causesbacillary dysentery " Humans are the only natural host , infection caused by fecal oral route.
- 10. Shigella - Culturalcharacteristics " Appear as non lactose fermenters on MacConkey agar. " Usually biochemically inert
- 11. Salmonella Classified as : "Salmonella species (non typhoidal salmonella) " Salmonella typhi " Human infections with salmonellae acquired via ingestion of food ,milk,water that is contaminated by human or animal excreta.
- 12. ! Appear asgram negative bacilli Salmonella - Microscopy
- 13. Salmonella typhi • Causestyphoid fever - the disease progresses through a bimodal course characterized by an early period of fever and constipation (1-2wks) where blood cultures are + and stool – ffd by diarrheic phase where stool + and bld – then ffd by a carrier state. " Humans are the only known reservoir for S.typhi
- 14. Salmonella - Culture Culturedon routine media Appear as non lactose fermenters Produce trace amounts of H2S.
- 15. Campylobacter jejuni " Mostimportant human pathogens amongst the campylobacters. " Common sources of human infection - ingestion of raw milk, partially cooked poultry, contaminated water.
- 16. Campylobacter jejuni -Microscopy " Presumptive diagnosis of campylobacter enteritis made by identifying gram negative gull-winged (curved) bacteria
- 17. Campylobacter jejuni -Culture " Isolated in the laboratory using several selective agars
- 18. Campy culture Isolated inthe laboratory using several selective agars
- 19. Vibrio cholerae " Agentof pandemic cholera in humans " Produces characteristic rice water stool (d/t toxin production)
- 20. Vibrio cholerae -Microscopy " - curved gram negative bacilli - darting motility on wet prep of stool
- 21. Vibrio cholerae -Culture " Grows well on selective media " Appear as smooth yellow colonies
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- 23. Yersinia enterocolitica " Swine-major reservoir of human strains. " Portal of entry - oral (infection settles at terminal ileum → ileitis → lymphadenitis→ acute enterocolitis.
- 24. Yersinia enterocolitica -Microscopy " pale staining gram negative cocco-bacilli
- 25. Yersinia enterocolitica -Culture " grows on selective agar best at room temp , appear as non lactose fermenters on MacConkey agar.
- 26. Yersinia enterocolitica -culture (bld agar)
- 27. Helicobacter pylori " Foundon mucous secreting epithelial cells of stomach. " Causes gastritis , peptic ulcer disease and linked to gastric adenocarcinoma and non -Hodgkins lymphoma.
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- 29. Helicobacter pylori -Microscopy " Appear as small curved gram negative bacilli.
- 30. Lab diagnosis " Microaerophiliic(10% CO2 , 5%O2 ,85%N2 ) " Take 3-5 days to grow " Can be cultured on non selective blood containing media on which they produce small transclucent grey colonies
- 31. Parasites - Classification •Protozoa (unicellular organisms) • Amoebae eg. Entamoeba histolyticum • Ciliates eg. Balantidium coli • Flagellates eg. Trichomonas vaginalis Giardia lamblia • Sporozoa eg. Plasmodium spp ,Toxoplasma gondii, Isospora belli, Cryptosporidium spp • Metazoa nematodes (roundworm) *intestinal eg. Ascaris lumbricoides Hookworms (Ancylostoma duodenale) Enterobius vermicularis Strongyloides stercoralis Trichuris trichiura * tissue eg filarial worms (Wuchereria bancrofti, Loa loa) cestodes (tapeworms) eg. Taenia spp Echinococcus granulosus trematodes (flukes) eg. Schistosoma spp.
- 32. Entamoeba histolytica -(Amoebiasis) • Two main clinical manifestations : intra-intestinal amoebiasis :amoebic dysentery extraintestinal amoebiasis :amoebic liver/lung abscesses Amoebic dysentery : • caused by pathogenic strains of E.histolytica - t/m via direct feacal oral route through contaminated water/food. • starts with vague abd symptoms that includes abdominal pains, 2/more unformed stools/day, diarrhea alternating with constipation, mucus streaked with blood, acute bowel symptoms with passage of much blood and mucus. Amoebic liver abscess: • possible even without preceding history of diarrhea and presents with weakness low grade fever RUQ pain
- 33. Entamoeba histolytica: withoutingested RBC
- 34. Entamoeba histolytica: withingested RBC
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- 36. Giardia lamblia " Majorworldwide public health problem. " In endemic areas (England, Russia,coastal areas of the Mediterranean)- common in children. " The cyst is resistant to the concentration of chlorine normally used for the treatment of domestic water supply.
- 37. Giardia lamblia -Clinical Features " Varies from asymptomatic carriage to severe diarrhoea with malabsorption. " Incubation period : 1-14 days (average 7 days) & usually lasts 1-3 wks. " Symptoms include diarrhoea, abdominal pain, bloating, nausea, and vomiting. " Can progress to chronic giardiasis with recurrent episodes and growth impairment in children
- 38. Giardia lamblia -Laboratory Diagnosis Cyst Trophozoite Macroscopy of stool: offensive odour, pale colour, fatty and floats in water (steatorrhoea)
- 39. Trichomonas vaginalis " Sexuallytransmitted flagellate. " Causes urethritis, vaginitis and cervicitis (“strawberry cervicitis”) " Incubation period 5-28 days.
- 40. Toxoplasma gondii " Isan animal coccidian parasite. " Causes Toxoplasmosis. " Modes of transmission: --ingestion of infected oocysts from food / raw meat / water contaminated with cat faeces. " Congenital toxoplasmosis is the most serious form of human infection.
- 41. Toxoplasma gondii -Clinical features " Is generally asymptomatic in immunocompetent people. " Immunosuppressed patients frequently present with CNS lesions, of which intracerebral mass lesions are the most common manifestation. " Congenital infection can present with stillbirth, cerebral damage, retinochoroiditis
- 42. Ascaris lumbricoides (Roundworm) "Largest nematode (roundworm) parasitizing the human intestine
- 43. Ascaris lumbricoides (Roundworm)Diagnosis • Definitive diagnosis depend on identification of typical eggs or worms in stools " Post-Barium meal X-Rays can show “wormball” " Worms are sometimes vomited or coughed up " Male 20cm long with curved tail/ Female 35cm
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- 45. Ascaris lumbricoides -Laboratory Diagnosis " Hookworm egg " Hookworm larva
- 46. Laboratory diagnosis " Scotchtape (“sticky tape”) is applied to the anus, then the tape is placed onto a slide and the eggs are seen microscopically
- 47. Schistosomiasis " Also knownas “bilharzia” " 3 spp. commonly cause disease in humans i.e. S. haematobium, S. mansoni, S. japonicum depending on the geographical location. " Infection is highest in children 10-15yrs of age.
- 48. Schistosomiasis - Clinicalfeatures " Cercarial penetration through the skin: causes swimmers itch. " Acute Schistosomiasis: Katayama Fever " Retained eggs: S.haematobium: Early symptoms: terminal haematuria dysuria frequency. Later complications: bladder calcifications obstructive uropathy, bladder carcinoma.
- 49. Schistosomiasis - Microscopy "S. haematobium Ovum has a terminal spine " S. mansoni Ovum has a lateral spine
- 50. Schistosomiasis - ClinicalFeatures " Infection with the adult tapeworm rarely produces any serious effects. Can cause minor abdominal symptoms. " T. saginata is not of clinical importance in humans. Causes major economic losses due to condemnation of beef carcasses. " T. solium : ingestion of the egg can cause neurocysticercosis which is a major cause of epilepsy in developing countries
- 51. Schistosomiasis - Laboratorydiagnosis " Ova of T. solium and T. saginata are indistinguishable on microscopy
- 52. " T. saginata "T. solium (has hooklets)