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Diarrheal Diseases in Underdeveloped Countries

Diarrheal Diseases in Underdeveloped Countries. Worldwide Problem More than 10,000 deaths per day On average, about 18 diarrheal episodes per year Primarily in children. Diarrheal Diseases in Developed Countries. Continues to be a problem 25 million enteric infections per year

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Diarrheal Diseases in Underdeveloped Countries

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  1. Diarrheal Diseases in Underdeveloped Countries • Worldwide Problem • More than 10,000 deaths per day • On average, about 18 diarrheal episodes per year • Primarily in children

  2. Diarrheal Diseases in Developed Countries • Continues to be a problem • 25 million enteric infections per year • 10,000 deaths per year in the U.S.A • Highest rate in children under 5

  3. Immunodiagnostics for Diarrheal Disease Clostridium difficile Entamoeba histolytica/dispar Giardia Cryptosporidium Clostridium perfringens Fecal Leukocytes Inflammatory Bowel/Irritable Bowel

  4. Clostridium difficile

  5. Clostridium difficile is a gram positive, spore forming bacillus • Now known to be the cause of pseudomembranous colitis (PMC)and antibiotic associated diarrhea(AAD) • Causes almost all cases of PMC but only 25% of AAD. The most common cause of nosocomial diarrhea

  6. Organism first described in 1935 - isolated from feces of normal infants and named Bacillus difficilis because of difficulty in isolation • Only recognized as a pathogen in late 1970s • Diarrhea is efficient method of spreading spores

  7. In early ‘80s Dr Wilkins and his research team at the Anaerobe Lab at Virginia Polytechnic Institute (VPI) isolated and characterized toxin A and toxin B of Clostridium difficile. Dr Bartlett at Johns Hopkins University had recognized that C.difficile produces two toxins in 1980

  8. Dr Wilkins’ research group also developed the first diagnostic test for the disease and developed and patented the antibodies subsequently used by all other companies for the development of their competitive EIAs. • The names Dr Wilkins and/or Dr Lyerly (the founders and co-owners of TechLab Inc) are to be found in the reference list of ALL competitive companies kit inserts

  9. Clinical Terms • Antibiotic Associated Diarrhea • Antibiotic Associated Colitis • Pseudomembranous Colitis

  10. Sequence of events leading to C.difficile infection • Alteration of normal gut flora • Nosocomial infection by C.difficile • Growth and production of toxins • Tissue damage by toxin A, exacerbated by toxin B • Diarrhea and colitis due to tissue damage and influx of fluid

  11. Biological Activities of Toxin A and B of C.difficile

  12. Are there unusual strains that may be missed with an ELISA that detects only toxin A?

  13. YES! Multicenter Evaluation of the Clostridium difficile TOX A/B TEST Journal of Clinical Microbiology, Jan 1998, p. 184-190 An Outbreak of Toxin A negative, Toxin B positive Clostridium difficile Associated Diarrhea in a Canadian Tertiary Care Hospital. Canada Communicable Disease Report, April 1999 Characterization of a Toxin A negative, Toxin B positive Strain of Clostridium difficile Responsible for a Nosocomial Outbreak of Clostridium difficile Associated Diarrhea Journal of Clinical Microbiology, July 2000, p. 2706-2714 Pseudomembranous Colitis Caused by a Toxin A- Toxin B+ strain of Clostridium difficile Journal of Clinical Microbiology, April 2000, p. 1696-1697

  14. These strains have caused fatalities in Europe and North America • Actual incidence (at this time) is unknown - we believe it is around 10%, however, a study in Israel showed an incidence of more than 66% in one hospital setting

  15. These strains do not lack toxin A - they only lack the region of the toxin A gene that codes for the antibody binding site -known as the receptor region.

  16. Analysis of A-B+ isolates by PCR • 52 A-/B+ isolates tested • All 52 were from clinical specimens that tested A-/B+ • All 52 have the same large deletion in Toxin A A+/B+ A-/B+ Antibody binding site-(repeat region) Toxin B Toxin A

  17. All Broad Spectrum Antibiotics cause C.difficile Infections • Not due to resistance of C.difficile • Due to susceptibility of normal flora • Diarrhea sometimes can be stopped by stopping the inciting agent

  18. Epidemiology of C.difficile Disease • <3% normal carrier rate in healthy adults • 50% or higher in infants usually asymptomatic • Outbreaks occur in hospitals and medical centers

  19. Transmission of C.difficile • Primarily a nosocomial pathogen - however can be present in the community (mainly a disease of the aged) • Spore former - study showed that spores spread on floor of clean hospital room could be isolated and cultured months later • Has been isolated from hands of health care workers, library books, medicalequipment, cords used to summon nurses, carpet etc.

  20. Benefits of TechLab TOX A/B II TEST • Has highest correlation with tissue culture (gold standard), highly sensitive and specific • Detects both toxins • Diluent stabilizes toxin for transport or storage

  21. Benefits of TechLab TOX A/B II TEST • Can be performed in as little as 40 minutes (rapid format) • Developed by the pioneers of C.difficile testing (Competitors use the TechLab patented monoclonal antibody) • No indeterminates, no repeat testing • Can be used with the TechLab stool preparation device to cut down on technician time and stabilize the toxin for transport

  22. Clostridium difficile Testing • Culture • Latex agglutination • Tissue Culture • ELISA

  23. Culture • Culturing is not standardized • Requires anaerobic techniques, special selective media and expertise not readily available in may labs • A toxin test has to be performed on the cultured isolates to determine whether the organisms is toxigenic or nontoxigenic • Organisms from asymptomatic patients can be isolated - these patients do not require antibiotic therapy • Organisms present in very low numbers can also be cultured - these may or may not cause disease

  24. Latex Agglutination • Detects glutamate dehydrogenase, an enzyme produced by both toxigenic and nontoxigenic C.difficile and some other Clostridia • Very low sensitivity and specificity

  25. Tissue Culture (Cytotoxicity Test) • Gold standard as it was the first test available and can detect picogram quantities of toxin B (remember, toxin B is the most potent cytotoxin known to man - toxin A is also cytotoxic but at the dilutions used in this test it has no cytotoxic effect). • Test requires that sample be diluted, centrifuged, filter sterilized and dispensed into the wells of a microtiter plate containing a confluent sheet of mammalian cells • Labor intensive and takes 24-48 hours for a result • Requires considerable expertise and specialized equipment

  26. ELISA Clostridium difficile Tests that are toxin A specific • TechLab TOX A TEST • Meridian Premier Toxin A • Bartels Prima (recently purchased by Trinity) • Alexon ProspecT Toxin A • Vidas CDA • Becton Dickinson Culturette CD • Biosite Triage • Becton Dickinson ColorPac Toxin A

  27. EIA TESTS that detect both toxin A and toxin B • TechLab TOX A/B TEST • Meridian Premier A+B

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