Mycobacterium and Associated Diseases Flashcards
What makes up the membrane of Mycobacterium?
- Mycolic acid
- Acyl lipid
- Lipoarbinomannan (LAM)
- Arabinogalactan
- Peptidoglycan porins and a lipid bilayer
What are the general morphologic characteristics of Mycobacterium?
- Unique cell wall
- high lipid content
- Mycolic acids, complex waxes, unique glycolipids (up to 60% of the dry weight of the organism)
- high lipid content
- Rod shaped
- Non motile
- Over 100 species and subspecies
- non pathogenic
- obligate intracellular pathogens
- opportunistic pathogens
What does the unique cell wall of Mycobacterium do?
- Ability to resist:
- Dehydration
- acid or alkali inactivation
- heat / cold
- several common antibiotics
- Common disinfectants
- Can survive in soil for up to a year
How well do mycobacterium grow?
- Very slow
- slow doubling times 12 - 24 hours
- Colonies arise in 2-6 weeks or longer
- rapid growers in 48 - 72 hours
What is the pathogenesis of Mycobacterium?
- Intracellular survival - most important virulence property
- Cellular antigen stimulate cell mediated and humoral immune responses
- immune response leads to granulomas
- Caseous necrosis at center of granulomas may lead to calcification or liquefaction
How is Mycobacterium diagnosed?
- Direct examination of the organism after acid-fast staining
-
Tuberculin skin test
- determine delayed-type hypersensitivity reaction
- Culture
- Antibodies by Agar-gel immunodiffusion, ELISA, CF and IFA
- PCR
Why does Acid-fast staining work with Mycobacterium?
- Complex cell wall retains carbol-fuchsin dye when decolorized with acid-alcohol
- Allows for differential staining
- other bacteria stain blue
What diseases are cause by Mycobacterium?
- Johne’s disease - ruminants
- Crohn’s disease - humans (?)
- Pulmonary tuberculosis - humans & animals
- Hansen’s disease - humans (leprosy)
- Feline leprosy
- Avian tuberculosis
What is the causative agent of Johne’s Disease?
Mycobacterium avium subspecies paratuberculosis
What animals does Johne’s Disease affect?
- Cattle
- Sheep
- Goats
- Deer
- Antelope
- Llamas
What are the symptoms of Johne’s Disease?
- Weight loss
- Diarrhea
- Bottle Jaw
- Submandibular Edema
What is the pathogenesis of Johne’s Disease?
- Infection results in granuloma formation
- Thickens intestinal wall and impairs function
- Diarrhea, poor absorption of nutrients
- Animal eats but rapidly lose weight
How is Johne’s Disease transmitted?
- Enters with healthy looking infected animal
- Spreads very slowly
- Infects very young animals
- contaminated feed
How is Johne’s Disease controlled?
- Prevent indroduction of infected animals
- Raise newborns in clean environment fed milk free of M. paratuberculosis
- Identify and remove infected animals
- Infected herds tested yearly
- Cull positives
What is the treatment for Johne’s Disease?
- Not curable by antibiotics
- Cost prohibitive
- Cull from herd
What is the causative agent of Bovine Tuberculosis (TB)?
- Mycobacterium tuberculosis
- M. bovis
- M. africanum
- M. microti
- M. canettii
What does Bovine Tuberculosis cause?
- Pulmonary disease
How is Bovine Tuberculosis contolled?
- Eradication program 1924
- milk pasteurization
- cull positive animals
How is Tuberculosis Transmitted?
- Aerosol
- Coughing humans or animals
- Contaminated unpasteurized milk
How is Tuberculosis diagnosed?
- Tuberculin skin test (DTHs)
- X-ray
- Culture
- ELISA - serum antibodies
What is the treatment for Tuberculosis?
- Combination therapy using anti TB drugs:
- Streptomycin
- P-aminosalicylic acid
- isoniazid
- Pyrzinamide
- cycloserine
- ethambutol
- rifampin
- Emergence of multi drug resistant pathogens is a major concern
What is the causative agent of Hansen’s Disease?
Mycobacterium leprae
What is Hansen’s disease?
- Leprosy
- Disease of skin and nervous system
- Found mostly in Asia, Africa, and SA
How is Hansen’s Disease transmitted?
- Close contact
- Exposure to infected armadillos
- nasal secretions and mammary ducts
What is the causative agent of Feline Leprosy?
Mycobacterium lepraemurium
What is Cat leprosy?
- Localized skin infection on the head and limbs
- Most reported cases in New Zealand
- Also in Pacific coast of US and CAN
- Affects those <3 years old
How is Cat Leprosy transmitted?
- Rats and mice
What is Mycobacterium avium ssp avium?
- Widespread in birds
- Affects all organs
- Ubiquitous in soil, water, bird droppings
- Causes Tuberculosis in people
- Common in swine
- Granulomas in lymph nodes of head and GI tract
- lesions present in 1-3% of slaughtered hogs
- Rare in cattle, dogs, cats, and people
- major concern for AIDS patients
