31 – Mycobacterium Flashcards
Microbiological characteristics
- Slow growing, non-motile rods
o Some take weeks to grow - Have ‘gram-positive’ peptidoglycan although DON’T stain using Gram’s procedure
o Presence of mycolic acid
o Cell wall component presents an important permeability barrier - Described as acid-fast
- Can be VERY challenging to work with
- Biocontainment level 2 or 3
- *M. tuberculosis!
Natural host or habitat
- Host associated: although survive for periods in environment
- ‘atypical’ ones are environmental organisms and readily survive in environment
Mycobacterium tuberculosis complex organisms: natural host or habitat
- Respiratory tract
- Feces
- Milk
- Urine
Mycobacterium avium supsp. paratuberculosis: natural host or habitat
- Feces
Mycobacterium tuberculosis complex
- Group of organisms associated with GRANULOMATOUS DISEASE
o Mammalian tubercle bacille - Very important zoonotic organism
- Zoonotic infections with other MTb complex
o M. bovis used to be very common cause of TB in Canada
Mycobacterium tuberculosis: primarily human disease
- 1/3 of global population latently infected
o Up to 10% could reactivate - Synergism with HIV
What animals is Mycobacterium bovis associated with disease?
- Human and ruminants
- *destructive lesions characterized by granulomatous, caseating lesions
- *not in Canada, but is in the states
Mycobacterium bovis in ruminants: several forms
- Often see no outward clinical signs: maybe only detected through surveillance
- Generalized
- Respiratory
- *long incubation, with period of latency
Generalized Mycobacterium bovis lesions
- Emaciation
- Lethargy
- Weakness
- Anorexia
Respiratory Mycobacterium bovis lesions
- Chronic, intermittent, moist cough
How is Mycobacterium bovis transmitted?
- Between contagious and susceptible animals through
o Nose-to-nose contact (cattle or infected wildlife)
o Ingestion of contaminated feed/water
What happens if there is a suspicion of a case? (Mycobacterium bovis)
- Quarantine
- Investigation
- Humane depopulation
- Cleaning and disinfection
- Compensation (market value of animals destroyed)
2 tests for Mycobacterium bovis (EXAM)
- Intradermal tuberculin skin test
- IFN-gamma blood test
Intradermal tuberculin skin test (Mycobacterium bovis) (EXAM)
- Very sensitive, less specific (can’t have false negatives!)
- Delayed type hypersensitivity (type IV)
- Cell mediated immunity
o In positive animals see swelling develop over 24-72 hours
IFN-gamma blood test (Mycobacterium bovis) (EXAM)
- Less sensitive, very specific (ID false positives)
- Blood collected from those who reacted to tuberculin test
- Exposed WBCs in blood to antigen: measure production of cytokine as a response