Gastrointestinal infections - bacteriology
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This is a series of lectures on microbiology, useful for both undergraduate and post graduate medical and paramedical students... This lecture covers cholera, typhoid, diarrhoea and dysentry
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Gastrointestinal infections - bacteriology
- 1. Gastrointestinal Infections Dr. Ashish V. Jawarkar, MD (Path)
- 2. Overview • Most infections of the g.i.t. are acquired through contaminated food – food poisoning • Food infection – − Bacteria like - Cholera, E. coli, Salmonella, shigella, − viruses like enterovirus, rotavirus, hepatitis A and E − Parasites like G. lamblia • Food intoxication – S. aureus, B. cereus, Cl. Perfringens, Cl. botulinum
- 3. Symptoms • Abdominal pain • Diarrhoea • Vomitting • Fever
- 4. Factors responsible for spread • Age – children more susceptible • Personal hygiene • Open air defecation • Food at road side stalls • Uncovered food
- 5. Vibrio Cholerae • Vibrio – vibrate – vibratory motility • Present in surface waters worldwide
- 6. • Morphology • Growth characteristics • Biochemical reactions • Resistance • Pathogenicity and virulence • Epidemiology • Diseases caused • Laboratory diagnosis • Treatment
- 7. Morphology • Short, curved comma shaped bacillus • Single polar flagella • Gram negative
- 10. • Morphology • Growth characteristics • Biochemical reactions • Resistance • Pathogenicity and virulence • Epidemiology • Diseases caused • Laboratory diagnosis • Treatment
- 11. Growth characteristics • Aerobic • Colorless colonies on mac conkey • Special media − Transport media − Enrichment media − Plating media
- 12. Transport media • VR medium (Venkatraman, ramkrishnan) • Cary blair medium
- 13. Enrichment media • Alkaline peptone water • Monsur’s taurocholate tellurite peptone water
- 14. Plating media • TCBS medium – thiosulfate, citrate, bile salts and sucrose
- 15. String test • Loopful of colonies mixed with drop of sodium deoxycholate in saline
- 16. • Morphology • Growth characteristics • Biochemical reactions • Resistance • Pathogenicity and virulence • Epidemiology • Diseases caused • Laboratory diagnosis • Treatment
- 17. Biochemical reactions • Cholera red reaction − Ferments glucose, mannitol, maltose, mannose and sucrose − Produces indole which gives red color
- 18. • Morphology • Growth characteristics • Biochemical reactions • Resistance • Pathogenicity and virulence • Epidemiology • Diseases caused • Laboratory diagnosis • Treatment
- 19. Resistance • Resistant to cold – refrigerated food may carry vibrio • Donot survive at room temperature / heating • Susceptible to common drugs like doxycycline
- 20. • Morphology • Growth characteristics • Biochemical reactions • Resistance • Pathogenicity and virulence • Epidemiology • Diseases caused • Laboratory diagnosis • Treatment
- 21. Cholera • Acute diarrhoeal illness • Painless ‘rice water’ stools • Copius vomitting • Fluid loss and dehydration
- 23. • Due to two toxins released by bacteria in intestine • Toxin A and B • Cause pouring of water from body into intestines • Extensive water depletion
- 24. • Morphology • Growth characteristics • Biochemical reactions • Resistance • Pathogenicity and virulence • Epidemiology • Laboratory diagnosis • Treatment
- 25. Epidemiology • Source – infected humans • Mode of transmission – contaminated water/food • Cholera spreads as sporadic/epidemic or pandemic forms • Large movement of people such as during fairs/festivals is associated with cholera spread
- 26. Sporadic • Short duration infection limited to a small area
- 27. Epidemic • Suddenly many cases are seen over a large area
- 28. Pandemic • Cases seen over a long period of time over continents • Till 19th century, cholera was mainly confined to India – mainly area of Ganga plains – Bengal • Total seven pandemics have been identified.
- 29. Seventh pandemic
- 31. • Morphology • Growth characteristics • Biochemical reactions • Resistance • Pathogenicity and virulence • Epidemiology • Laboratory diagnosis • Treatment
- 32. Lab diagnosis • Sample – stool – before administering antibiotics • Use transport medium • Dark field microscopy can be done for darting motility
- 34. • Plated on TCBS medium • Slide agglutination test • String test
- 35. • Morphology • Growth characteristics • Biochemical reactions • Resistance • Pathogenicity and virulence • Epidemiology • Laboratory diagnosis • Treatment
- 36. Treatment • More important is replacement of lost fluid • Antibiotics are of secondary importance • Doxycycline
- 37. Enterobacteria • Flora of large intestine • Classified on basis of growth on Mac Conkey’s medium − Lactose fermenters – E. coli, Klebsiella − Late lactose fermenters – shigella − Non lactose fermenters - Salmonella
- 39. Diarrhoea causing E. Coli ETEC Toxin causes release of water into intestinal lumen Watery diarrhoea EIEC Invade intestinal wall Dysentry Entero invasive E Coli Blood and mucous in stools EHEC Does not invade Bloody diarrhoea Entero hemorrhagic Toxin release Colitis Entero toxicogenic E Coli EPEC Entero pathogenic Infant watery diarrhoea
- 41. • E coli cause − − − − UTI Diarrhoea Pyogenic infections Septicemia • Spread – feco oral route
- 42. Salmonella – Enteric Fever - Typhoid • Also causes gastroenteritis • Motile gram negative rods • Peritrichous flagella
- 43. Salmonella – Enteric Fever - Typhoid • Also causes gastroenteritis • Motile gram negative rods • Peritrichous flagella
- 45. Growth characteristics • Colorless colonies on Mac conkey – Non lactose fermenters • Jet black colonies on Wilson and Blair due to production of H2S
- 46. Growth characteristics • Enrichment media − Selenite F broth − Tetrathionate broth
- 47. Diseases caused • Enteric fever • Gastroenteritis • Septicemia
- 48. Enteric Fever (Typhoid) • Pathogenesis
- 51. Clinical course • Gradual onset with fever, abdominal pain and constipation/diarrhoea • Step ladder fever with bradycardia • Spleen and liver are enarged • Rose spots on skin in second week
- 52. Complications • Intestinal perforation • Hemorrhage • Shock • Cholecystitis • Osteomyelitis
- 53. Epidemiology • Source – food handlers/cooks − Carriers – • Convalescent carriers – shed bacilli for 3 weeks to 3 months after cure • Chronic carriers – more than 3 months after clinical cure
- 54. Typhoid Mary • New york cook – infected more than 200 persons – caused atleast 7 outbreaks
- 55. Lab diagnosis • Cases – Widal test, blood culture • Carriers – isolation from bile
- 56. Widal test
- 58. Blood culture / Bile culture • Take 45ml patient blood in bile broth • Send to lab • Cultured on Mac Conkey • Lactose non fermenting colonies
- 59. Treatment • Chloramphenicol • Ampicillin • Co trimoxazole
- 60. Prophylaxis • Best is improved sanitation • Live oral vaccine – typhoral • Injectable vaccine – typhim vi • Protection lasts 3 years, booster required afterwards
- 61. Shigella – BACILLARY DYSENTRY • DYSENTRY – bacillary (shigella) and amebic (parasitic) • Also caused by EIEC, Campylobacter
- 62. • Gram negative rods • Lactose non fermenters on Mac conkey • Classified according to mannitol fermentation − Sh dysenteriae – mannitol non fermenter − Sh flexneri, sh bodydii and sh sonnei – mannitol fermeters
- 63. Bacillary dysentry • Bacilli infect intestinal epithelial cells • Spread to submucosa • Inflammatory reaction with capillary thrombosis • Sloughing and necrosis of mucosa • Ulcers
Notas do Editor
- Age; EPEC and rotovirus tend you affect young children Hygiene: fecooral Acidity: protective barrier, low inoculm Motility: expel the pathogens. Antimotility assoc with prolonged fever shedding shigella, complication c diff, HUS in ETEC Flora: ex cdiff