L8 Infectious Diarrhea

Objectives

1. Understand the global burden, public health impact, and high-risk population classification

2. Distinguish different types of diarrhea via clinical presentation, etiology, and pathophysiology

3. Understand how infectious diarrhea → long-term clinical sequalae (resulting separate disease) and their causative pathogens

4. GI infection prevention

Notes

1. T/F: Infectious Diarrhea has a small morbidity and mortality rate

   • False, leading cause of hospitalization and outpatient visits

2. Acute GI Infections causes what as the 2nd cause of mortality in children < 5

   • Dehydration

3. What is the criteria for Diarrhea

   • decreased BM

   • 3 or more stool passings per day

4. What are the symptoms

   • N/V

   • abdominal pain, cramps, bloating, flatulence

   • fever, bloody stool, fecal urgency, mucosal inflammation

5. What is the criteria for Acute Diarrhea

   • < 7 days

6. What is the cause of Acute Diarrhea

   • Gastroenteritis

7. What is the criteria of Persistent Diarrhea

   • 14-30 days

8. What is the criteria of Chronic Diarrhea

   • > 30 days

9. Although etiology is rarely identified, what is the leading cause of Infectious Diarrhea

   • Viruses

     • Norovirus → 90% Gastroenteritis

     • Rotavirus → common in infants/children

     • Astrovirus, Enteric Adenovirus, Pestivirus, Coronavirus, Enterovirus

10. What are the two types of Infectious Diarrhea

    • Watery/Enterotoxigenic (strain of E. coli)

    • Inflammatory/Bloody

11. What is the mechanism of Watery/Secretory/Enterotoxigenic Diarrhea

    • Enterotoxins from E. coli/Norovirus/Rotavirus → colon → disrupts ion transport → Decreased Na+ Absorption and Increase Cl- Secretion → excess secretion → Dehydration and Electrolyte Imbalance

12. What is the mechanism of Inflammatory Diarrhea/Dysentery (bloody)

    • pathogens disrupt mucosal barriers → immune response (inflammation) → bloody stool

13. What systemic symptoms does Inflammatory Diarrhea cause

    • Fever, Malaise, possible Sepsis

14. T/F: Both Secretory and Inflammatory Diarrhea have Leukocytes present in the stool

    • False, only Inflammatory diarrhea

15. What Pathogens can result in Inflammatory Diarrhea? Hint: CHEESY

    • Campylobacter spp.

    • Hemorrhagic E. coli (STEC)

    • Enteroinvasive E. coli

    • Entamoeba histolytica

    • Salmonella spp.

    • Shigella spp.

    • Yersinia enterocolitica

16. What possible complications can result from Inflammatory Diarrhea

    • Hemolytic Uremic Syndrome (HUS)

      • EHEC and Shigella Dysenteriae

    • Bacteremia

      • Salmonella and Campylobactor

    • Reactive Arthritis

      • Post-Infection complications

17. What are high risk populations of infectious diarrhea

    • Infantile/children and elderly

    • travelers/campers

    • chronic care facility patients

    • abroad military personnel

    • immunocompromised

    • pregnant

      • higher complications risk with infections (ex. Salmonella)

    • chronic illnesses

      • DM, Inflammatory Bowel Disease, Malnutrition

18. Explain the Pathophysiology of Infectious Diarrhea

    • Fluid Absorption

      • excess secretion and impaired absorption

    • Mucosal Integrity

      • damaged and/or pathogen invasion → inflammation

    • Peristalsis

      • disrupted motility → diarrhea or spasms

    • Immune Activation

      • exaggerated response → tissue dmg

    

19. T/F: Stool cultures are recommended in mild-mod secretory diarrhea

    • False; used for Dysentery, Mod-Severe, > 7 days, Immunocompromised, Outbreaks

20. What pathogens can be identified via Stool Cultures

    • can identify Campylobacter, Salmonella, Shigella

21. When are Blood Cultures used

    • ≤ 3 months old

    • systemic manifestations

22. When is Population-Specific Testing used

    • Outbreak investigations

    • Healthcare or Food Industry workers

    • Travelers and High-risk populations

23. What Inflammatory Biomarkers that are taken note of

    • Serum C-reactive Protein (CRP)

    • Fecal Polymorphonuclear Cells

24. What does Stool Cultures detect

    • Bacterial Pathogens

25. What dos Microscopy detect

    • Parasites via Special Strains

26. What does Antigen Testing detect

    • Viral/Protozoal Infection

27. What are Culture-Independent methods

    • modern molecular diagnostics that fast and identifies multiple pathogens

      • high sensitivity

    • **preferred method that’s FDA approved

    • ex. Multiplex PCR Panels

28. T/F: Culture-Independent methods has higher diagnostic yield compared to traditional methods

    • True

29. What are the limitations to Culture-Independent methods

    • may detect non-viable or asymptomatic carriage of pathogens

    • can’t provide Isolates for further analysis

      • ex. antimicrobial sensitivity test

      • can’t identify etiology?

30. T/F: There should be routinely testing for infectious diarrhea

    • False — self limiting, high costs and low accessibility for advanced diagnostics

31. What populations are more likely to experience severe complications from Dysenteric Diarrhea

    • < 5 and elderly

32. What is the most common complication of Infectious Diarrhea

    • Bacteremia

      • can result in systemic issues

33. What is Irritable Bowel Syndrome (IBS)

    • GI disorder → recurrent abdominal pain and altered bowel habits

    • possible complication that persists 3+ months after infectious diarrhea

34. What is the pathophysiology of IBS

    • persistent, mild gut inflammation

    • altered microbiota

    • increased gut permeability and visceral hypersensitivity

35. T/F: IBS is typically caused by viral pathogens

    • False, Bacterial and Protozoal

36. What are Risk Factors for IBS

    • severe initial infection

    • prolonged illness

    • female

    • psychological stress

37. What is Hemolytic Uremic Syndrome (HUS)

    • Triad of Acute Kidney Injury (AKI), Thrombocytopenia (low platelets), and Microangiopathic Hemolytic Anemia

38. What is the Pathophysiology of Hemolytic Uremic Syndrome HUS

    • Shiga toxin dmgs Endothelial Cells → Platelet Aggregation and Microvascular Thrombosis (blood clots)

39. What pathogens are involves with Hemolytic Uremic Syndrome HUS

    • Enterohemorrhagic E. coli (EHEC)

      • common

    • Shigella dysenteriae

      • less common

40. What are the symptoms of Hemolytic Uremic Syndrome (HUS)

    • Hematuria, Oliguria, Pallor (pale), Fatigue

41. What are long-term complications of Hemolytic Uremic Syndrome (HUS)

    • Impaired Kidneys

    • HTN

42. What are Hemolytic Uremic Syndrome (HUS) prevention methods

    • Avoid anti-motility agents and antibiotics with EHEC infections (can increase toxin release)

43. What is Reactive Arthritis

    • Autoimmune condition with Arthritis, Conjunctivitis, and Urethritis that occurs weeks after infection

44. What is the Pathophysiology of Reactive Arthritis

    • anti-motility agents and antibiotics with EHEC infections (can increase toxin release)

45. What are common pathogens that cause Reactive Arthritis

    • Salmonella, Shigella, Campylobacter, Yersinia

46. What are symptoms of Reactive Arthritis

    • Joint pain and swelling

      • knee, ankles, toes

    • typically resolves in weeks to months

47. How is Reactive Arthritis treated?

    • Anti-inflammatory drugs

    • Physical Therapy

48. That is Traveler’s Diarrhea

    • multiple unformed stools a day with abdominal pain or cramps occurring after arrival

49. How is Traveler’s Diarrhea risk determined?

    • Destination

      • Asia, Middle East, Africa, Latin America

50. What pathogens can cause Traveler’s Diarrhea

    

51. What are symptoms of Traveler’s Diarrhea

    • mild cramps, urgent and loose stools, severe abdominal pain, fever, vomiting, bloody stool, anorexia, malaise

52. What are the different types of Traveler’s Diarrhea

    • Mild diarrhea:

      • tolerable, not distressing, does not interfere with planned activities

    • Moderate diarrhea:

      • distressing or interfering with planned activities

    • Severe diarrhea: incapacitating or completely prevents planned activities; all bloody diarrhea

    • Persistent diarrhea:

      • lasting >2 weeks

53. What are preventative measures of Traveler’s Diarrhea

    • fully cooked and hot food

      • uncooked meat/shellfish

    • avoid

      • salads and uncooked vegetables

      • unpasteurized fruit juices and dairy

      • unwashed and peeled fruit

      • ice

    • drink purified or carbonated bottled water

54. What is Clostiridioides difficile (C. diff)

    • bacteria that can cause life-threatening diarrhea

    • most associated with antibiotic intake

    • most common HAI

55. What pathogen characteristics does C. diff has

    • Anaerobic

    • Spore-forming Gram Positive Rod

      • spores resist GI tract acidity

    • produces Toxin A and B → mucosal damage → Pseudomembranous Colitis (yellow plaque on epithelium)

    

56. How is C. Diff transferred

    • Fecal-Oral

57. What are signs and symptoms of C Diff

    • Secretory Diarrhea (> 3 per day)

    • fever, loss of appetite, nausea, abdominal pain/tenderness

    • Significant Leukocytosis (high numbers)

58. What are the Risk Factors of C. Diff

    • Antibiotics

      • Clindamycin, Cephalosporin, Ampicillin, Amoxicillin, Fluoroquinolones

    • > 65

    • Hospital stay / Surgery

    • Chronic illness or weak immune system

    • Inflammatory Bowel Disease

    • prev treatment of C. Diff — 20% relapse

      • 40% without risk factors

59. T/F: Only stools from patients with diarrhea should be tested for C. diff

    • True

60. What tests are considered if there is watery stool and C. diff suspicion

    • GDH (glutamate dehydrogenase)

    • EIA Toxin A and B

    • Fecal cultures

    • PCR Antigen testing

61. T/F: Repeating tests is encouraged

    • False

62. T/F: Clinical response is based on symptom resolution

    • true

63. How long does shedding occur after treatment

    • 1 month

64. What are C. diff complications

    • Pseudomembranous colitis

    • Toxic megacolon

    • Colon perforations

    • Sepsis

    • Death

65. What are goals of rehydration therapy

    • Resolve fluid losses

    • Correct electrolyte imbalances (if applicable)

    • Correct metabolic acidosis (if applicable)

    • Breastfeeding should continue for breastfed infants

      • Start refeeding at the start of rehydration

      • “BRAT” diet – bananas, rice, applesauce, toast

      • Avoid foods high in fiber, salt and/or sugar

66. Counseling

    • Wash hands

    • Infection control practices when caring for patients with diarrhea

    • Food safety practices

    • Avoid swimming and sexual contact when symptomatic

    • Vaccines

      • Rotavirus: all infants

      • Typhoid: adjunct for travelers to moderate/high risk areas

      • Cholera: all travelers to high cholera areas