What’s New in Poo

1. What’s New in Poo A lighthearted review of the use of human feces for the diagnosis and treatment of human gastrointestinal illnesses from the tainted viewpoint of a warped Microbiologist SOMC Grand Rounds January 6, 2012 Timothy R. Cassity, Ph. D. Microbiologist

2. Sorry Winnie, this presentation is about poo, not Pooh

3. Diagnostic Use of Stool • Symptomatic patients – GI complaints • Most of related to an infectious etiology • Asymptomatic patients • Most of screening for potential colon cancers

4. Symptomatic • Most common symptom is diarrhea • Lower GI tract • Dyspepsia, pain, etc • Upper GI tract

5. What’s not very new • Routine stool culture • Useful for Salmonella, Shigella, Campylobacter, and Escherichia coli O157 infections

6. What’s not very new • Routine stool culture • Misses some strains of enteropathogenic or enterotoxigenic E. coli.

7. Campylobacter EIA • An enzyme immunoassay is being evaluated at SOMC for the detection of Campylobacter species. • Can be done in < 30 minutes (culture takes 2 – 3 days) • Only need one per patient per illness • Slightly more sensitive than culture

8. Shiga-Toxin EIA • An enzyme immunoassay is being evaluated for the detection of shiga toxin-producing strains of E. coli • Requires 16 – 40 hours (culture takes 2 – 3 days) • Only need one per patient per illness

9. Shiga-Toxin EIA • An enzyme immunoassay is being evaluated for the detection of shiga toxin-producing strains of E. coli • Significantly more sensitive than culture • Detects enterotoxigenic E. coli other than O157 (increases sensitivity about 50%)

10. What’s not very new • Routine Ova and Parasite Exam • Very low yield with immunocompetent patients with no travel history

11. What’s not very new • Routine Ova and Parasite Exam • Useful for patients with unexplained anemia (Strongyloides stercoralis)

12. What’s not very new • Routine Ova and Parasite Exam • Ascaris lumbricoides found in rare instances.

13. SOMC Ova and Parasite

14. Cryptosporidium/Giardia lamblia DFA • Direct fluorescent antibody for Giardia lamblia and Cryptosporidium parvum. • Can be done in less than 1 hour • Much more sensitive for finding these organisms, particularly Cryptosporidium, than traditional ova and parasite exam.

15. Parasites – Recommended Algorithm • Order only Giardia lamblia/Cryptosporidium DFA on a single stool specimen on patients over 12 years old unless the patient is anemic, immunosuppressed or has a significant travel history.

16. Clostridium difficile

17. Clostridium difficile • An anaerobic, spore-forming gram positive bacillus, found mostly in the GI tract of mammals. • Both toxin-producing and non-toxin-producing strains exist • C. difficile culture alone not useful -detects both types

18. Clostridium difficile • Both toxin-producing and non-toxin-producing strains exist • GDH (Glutamate dehydrogenase) detects C. difficile, but detects both types • GDH can be used to rule out C. difficile, but not definitively diagnose it.

19. Clostridium difficile • Toxigenic culture (Reference Method) • Very sensitive and specific • Culture C. difficile, then test isolate that is cultured for toxin production or toxin genes • Good academically, not useful clinically • Requires 2 or more days to a negative result, 3 days to positive result

20. Clostridium difficile • Up until the last 2 years, most clinical labs used (and >90% still do) C. difficile toxin tests (either toxin A, or toxin A & B combined)

21. Clostridium difficile • Present day “state of the art” testing is an amplified DNA probe for a unique genomic region found only in the toxigenic strains.

22. Clostridium difficile • Our experience with amplified probe: • Increased sensitivity, 29% better than C. difficile toxin testing • Correlates well (>95% agreement) with toxigenic culture, the recognized reference method.

23. Clostridium difficile • Potential shortcomings of amplified DNA probes: • Excellent sensitivity – can detect as few as 16 C. difficile toxin gene copies per 50 microliters of stool • Must correlate with clinical information! • Presence of C. difficile does not confirm a diagnosis of C. difficile-associated disease.

24. Clostridium difficile • Potential shortcomings of amplified DNA probes: • Toxigenic C. difficile is found in many people who have no symptoms

25. Clostridium difficile • Potential shortcomings of amplified DNA probes: • Only method FDA approved for pediatrics, but remember children under 2 years of age have a high carriage rate, up to 50%.

26. Clostridium difficile • Specimen requirements • Specimens only accepted on symptomatic patients (i.e. diarrhea stool) • Rejected for testing: • Rattler’s • Formed stool • Stick Test negative (applicator stick stands)

27. Clostridium difficile • Specimen requirements • Specimens only accepted on symptomatic patients (i.e. diarrhea stool) • Acceptable specimens: • Liquid stool (takes shape of container) • Stick Test Positive (applicator stick falls)

28. Clostridium difficile • Specimen requirements • Because sensitivity is >95%, no more than 1 specimen needed • One specimen per patient per week, unless approved by the Microbiologist or Pathologist

29. Clostridium difficile • Specimen requirements • No lab test is indicated for “test of cure.” Resolution of diarrhea is sufficient.

30. Clostridium difficile - Treatment • Adequate treatment involves two dimensions • Eradication of toxin-producing C. difficile • Re-growth of normal bowel flora (particularly anaerobic flora)

31. Clostridium difficile - Treatment • Eradication of toxin-producing C. difficile • Metronidazole not effective for moderate to severe cases • Kills C. difficile OK, but kills anaerobic GI flora better • Treatment effective initially, but recurrence common

32. Clostridium difficile - Treatment • Eradication of toxin-producing C. difficile • Oral vancomycin is the agent of choice • Less toxic to normal GI anaerobes • A taper regimen is preferable – antibiotics kill only vegetative cells. • Longer coverage is necessary to control germinating spores • Longer coverage is necessary to allow re-growth of normal anaerobic GNRs.

33. Clostridium difficile - Treatment • Fidaxomycin • Less toxic to normal bowel flora than metronidazole or vancomycin • Compared to vancomycin 125 mg qid x 10 to 14 days, fidaxomycin had a lower relapse rate. • Expensive – standard course of therapy approximately $2,800 (wholesale price)

34. Clostridium difficile - Treatment • Re-growth of normal bowel flora (particularly anaerobic flora) • Will re-grow eventually if not assaulted • In recurrences more aggressive replacement is necessary

35. Clostridium difficile - Treatment • Re-growth of normal bowel flora (particularly anaerobic flora) • Stool transplant is effective in >90% of cases • Stool transplant involves a lot of testing of donor stool (which takes several days to complete), and is not aesthetically pleasing • “Synthetic” stool developed for this purpose

36. Therapeutic Use of Human Feces

37. Fecal Transplant • Used primarily to treat Cl. Difficile associated disease

38. Fecal Transplant • How they are performed:

39. Fecal Transplant • How they are performed: • Obtain approximately 200 – 300 grams of feces from a close, healthy donor

40. Fecal Transplant • How they are performed: • Donor stool is screened for: • Typical and atypical enteric pathogens (stool culture, Y. enterocolitica, A. hydrophila, and others) • Ova and parasites • The donor is screened serologically for: • Hepatitis A, B, and C • HIV-1 and HIV-2 • Syphilis

41. Fecal Transplant • How they are performed: • The recipient is screened for: • Hepatitis A, B, and C • HIV-1 and HIV-2

42. Fecal Transplant • How they are performed: • Recipient is treated with oral vancomycin 500 mg bid for 3 – 4 days (to kill vegetative C. difficile cells)

43. Fecal Transplant • How they are performed: • If donor stool is suitable, 200 – 300 grams of donor feces is blended with 200 – 300 mL of saline to make a slurry • Donor stool slurry is filtered through a coffee filter to remove particulate matter

44. Fecal Transplant • How they are performed: • Donor stool is “implanted” in the recipient via as nasogastric tube, colonoscope, or enema.

45. Fecal Transplant • Stool transplants are effective in >90% of cases • Used only for patients with recurrences • average duration of C. difficile in study was 11 months • 77 patients studied • 70 (91%) resolved within 6 days of treatment Reference: Shefchik, C. 2011. Clostridium Difficile Treated By Fecal Microbiota Transplant. Presented at the American College of Gastroenterology's 76th Annual Scientific Meeting, Oct. 28-Nov. 2 in Washington, D.C

46. Stools and Asymptomatic Patients

47. Asymptomatic Patients • Most tests are methods of screening for GI bleeding or potential colon cancer • Tests that detect GI bleeding • Tests that detect genetic changes associated with cancer cells

48. Hemocult (guaiac) Testing • Traditional test for occult blood • Easy to do • Inexpensive • Sensitivity • Many interfering substances • Dietary changes may be necessary before collecting stool specimen

49. Immunochromatographic Testing for Human Hemoglobin (FOBT) • Traditional test for occult blood • Easy to do, but more expensive than Hemocult • Sensitivity much better (approximately 300 X) than Hemocult • Few or interfering substances • Dietary changes not necessary before collecting stool specimen

50. Comparison of iFOBT and Hemocult