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BACTERIOLOGY - 2 > 31 – Mycobacterium > Flashcards

31 – Mycobacterium Flashcards

1
Q

Microbiological characteristics

A
  • 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!
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2
Q

Natural host or habitat

A
  • Host associated: although survive for periods in environment
  • ‘atypical’ ones are environmental organisms and readily survive in environment
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3
Q

Mycobacterium tuberculosis complex organisms: natural host or habitat

A
  • Respiratory tract
  • Feces
  • Milk
  • Urine
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4
Q

Mycobacterium avium supsp. paratuberculosis: natural host or habitat

A
  • Feces
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5
Q

Mycobacterium tuberculosis complex

A
  • 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
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6
Q

Mycobacterium tuberculosis: primarily human disease

A
  • 1/3 of global population latently infected
    o Up to 10% could reactivate
  • Synergism with HIV
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7
Q

What animals is Mycobacterium bovis associated with disease?

A
  • Human and ruminants
  • *destructive lesions characterized by granulomatous, caseating lesions
  • *not in Canada, but is in the states
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8
Q

Mycobacterium bovis in ruminants: several forms

A
  • Often see no outward clinical signs: maybe only detected through surveillance
    1. Generalized
    1. Respiratory
  • *long incubation, with period of latency
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9
Q

Generalized Mycobacterium bovis lesions

A
  • Emaciation
  • Lethargy
  • Weakness
  • Anorexia
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10
Q

Respiratory Mycobacterium bovis lesions

A
  • Chronic, intermittent, moist cough
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11
Q

How is Mycobacterium bovis transmitted?

A
  • Between contagious and susceptible animals through
    o Nose-to-nose contact (cattle or infected wildlife)
    o Ingestion of contaminated feed/water
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12
Q

What happens if there is a suspicion of a case? (Mycobacterium bovis)

A
  • Quarantine
  • Investigation
  • Humane depopulation
  • Cleaning and disinfection
  • Compensation (market value of animals destroyed)
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13
Q

2 tests for Mycobacterium bovis (EXAM)

A
  1. Intradermal tuberculin skin test
  2. IFN-gamma blood test
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14
Q

Intradermal tuberculin skin test (Mycobacterium bovis) (EXAM)

A
  • 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
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15
Q

IFN-gamma blood test (Mycobacterium bovis) (EXAM)

A
  • 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
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16
Q

What are the 2 wildlife populations in Canada that are reservoirs? (Mycobacterium bovis) (EXAM)

A
  • Wood bison in N. AB and NWT
  • Elk in riding mountain national park MB
17
Q

What are some other wildlife reservoirs of Mycobacterium bovis in other parts of the world?

A
  • European badgers
  • Bushtail possum
  • Wild boar
18
Q

Mycobacterium tuberculosis in people

A
  • High burden in low income countries
  • Fewer deaths in 2019 than 2000
  • 8th most common cause of death in developing countries
  • *decline in Canada: very uncommon
    o Non-indigenous Canadian born: 0.3=very low
    o Inuit: 135.1!
19
Q

Mycobacterium avium subsp. Paratuberculosis (Johne’s disease): clinical signs

A
  • Chronic, contagious granulomatous enteritis
    o Persistent diarrhea
    o Weight loss
    o Debilitation
    o Animals NOT generally fibrile or depressed
    o 50% are sub-clinical
  • *thickening of distal small intestine characteristic LESION
20
Q

Mycobacterium avium subsp. Paratuberculosis (Johne’s disease)

A
  • Slowly progressive disease: months to years
    o Don’t see clinical signs in animals under 2 years old
  • Also causes disease in other ruminants
  • Worldwide distribution
  • NO treatment options
  • NO vaccines
21
Q

Mycobacterium lepraemurium (feline leprosy)

A
  • CHRONIC
  • Disease characterized by singular or multiple nodules
  • Cutaneous lesions mostly on: head, neck, forelimbs
  • Seems more common in costal areas
22
Q

How do you treat Mycobacterium lepraemurium (feline leprosy)?

A
  • **surgical excision
  • Adjunctive antimicrobials
23
Q

Mycobacterium leprae (leprosy) in humans

A
  • Slowly progressing disease of skin, peripheral nerves, eyes and upper respiratory tract
  • Though to be genetic predisposition (only ~5% people susceptible)
  • Easily treated with antimicrobials
  • in America’s it is associated with ARMADILLO contact (S. US, S. America)
24
Q

Many Mycobacterium spp. isolated from domestic animals and humans

A
  • suspect with chronic, granulomatous infections
    o failed rounds of antibiotics
  • *specialist consultation is a must!
    o ID can be challenging
    o Varying susceptibility between species within genus
25
Q

Sample collection: M. bovis

A
  • PPE required
  • Lymph nodes
  • Lung tissues
  • Other lesions
26
Q

Sample collection: M. avium subsp. Paratuberculosis

A
  • Feces
  • Ileal lymph nodes
  • Blood
27
Q

Sample collection: M. lepraemurium

A
  • Tissue biopsies
28
Q

Lab ID options

A
  • Intradermal testing
  • Culture: MAP is very slow!
  • PCR
  • Acid fast stained smears
  • Serology
  • Histology
29
Q

Intradermal testing: false positives

A
  • Cross reactivity with other Mycobacterium species
  • VACCINATION: hug challenge and why we do not vaccinate in Canada
30
Q

Intradermal testing: false negatives

A
  • Improper handling of reagents or improper testing procedure
  • MUST be licensed by CFIA to perform this test
31
Q

Zoonotic/interspecies transmission

A
  • *Generally broad host range
  • Zoonotic
  • MAP (M. avium subsp. paraTB) associated with Crohn’s disease
  • M. avium associated with HIV patients
  • M. lepraemurium NOT considered zoonotic
32
Q

In US: M. bovis is responsible for 2% of cases of TB

A
  • Transmission through contaminated or unpasteurized dairy
    o Pasteurization is key
  • Contact with infected tissues when hunting
33
Q

Treatment options

A
  • Susceptibility testing done by agar dilution
  • Agriculture animals: antimicrobial therapy NOT done
  • Companion animals: polypharmacy necessary to prevent development of resistance
    o Specialist consultation
    o Widely varying intrinsic resistance

BACTERIOLOGY - 2 (16 decks)

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