Exam 3: Mycobacteria Flashcards
What is mycobacteria loosely classified by?
Mycobacterium tuberculosis complex
What makes up the mycobacterium tuberculosis complex?
M. tuberculosis
M. bovis
M. africanum
M. microti
What is non-tuberculos mycobacteria further classification based on?
Growth rate and pigment production (Runyon group)
What does M. scrofulaceum cause?
Tuberculosis lesion
What does M. avium cause?
Avian tuberculosis
What does M. intracellulare cause?
Avian tuberculosis
What are the general characteristics of mycobacteria?
Obligate aerobic
Non-spore forming
Non-motile
What does the growth of mycobacteria require?
Complex egg-enriched media, such as Dorset’s egg medium, Lowenstein-Jensen agar, or Herrold’s egg yolk agar medium
What does mycobacteria make a living in?
Macrophage: intracellular parasite
What do you need to stain mycobacteria? Why?
Acid fast stain because of mycolic acid and WaxD
What does the cell wall of mycobacteria consist of?
Mycolic acid Cord factor (lipoarabinomannan, generated from trehalose dimycolate) WaxD (peptidoglycan)
What is the tubercle bacilli recognized in humans?
M. tuberculosis
What is the tubercle bacilli recognized in bovine?
M. bovis
What is the tubercle bacilli recognized in avian?
M. avium complex (M. avium, M. intracellulare, and M. scrofulaceum)
Can the 3 tubercle bacilli species cause disease only in the species they are recognized in or can they produce infection in host species other than their own?
They can produce infection in host species other than their own
What is M. bovis a major cause of?
Human TB before the eradication program implemented in 1924
What reduced M. bovis infection from 5% in 1917 to less than 0.001% currently?
Milk pasteurization and slaughtering all tuberculin skin test positive animals
What is the attenuated live M. bovis vaccine used?
Bacillus Calmette-Guerin (BCG)
Can the BCG vaccine be used in the US?
No, federal law prohibits it
What happens to inhaled bacilli of M. bovis?
Phagoctyosed by alveolar macrophages that allow thee mycobacteria to proliferate
What is formed when the mycobacteria proliferate?
Primary focus
How is the classic tubercle formed from a M. bovis infection?
Purulent to caseous, necrotic center may calcify, and the lesion may become surrounded by granulation tissue and a fibrous capsule to form the classic tubercle
Describe the immunity associated with M. bovis
Cell-mediated immunity, delayed-type hypersensitivity
When are clinical signs of a M. bovis infection evident?
In advanced disease
What is used for antemortem diagnosis of M. bovis
The intradermal tuberculin tests
What is the intradermal tuberculin tests based on?
Delayed-type hypersensitivity
What are the official tuberculosis tests approved by the USDA?
Caudal fold tuberculin (CFT) test
Cervical tuberculin (CT) test
Comparative cervical tuberculin (CCT) test
Bovine interferon gamma assay (cattle only)
When are CCT injections given?
Within 10 days following CFT injection or more than 60 days following CFT injection
When must blood samples be collected for bovine interferon gamma assay?
Between 3 and 30 days after injection of bovine tuberculin
What does the media contain that grows M. lepraemurium?
Cytochrome C and α-ketoglutarate
What is M. leprae the cause of?
Leprosy in humans
What has M. leprae been found in?
Spontaneously occurring disease in armadillos
Describe M. avium infection
Ubiquitous in the environment
Produces disease primarily in birds
Birds are natural host
Serotypes 1, 2, and 3 are usually more virulent in birds
What is M. avium subs. paratuberculosis a causative agent of?
Johne’s Disease
What does M. avium subs. paratuberculosis form rough colonies on?
Middlebrook agar medium
What does in vitro growth of M. avium subs. paratuberculosis require?
An iron-transport compound known as mycobatin J
What is M. avium subs. paratuberculosis capable of even though it is not able to grow and multiply in the environment?
It is extremely hardy and may remain in contaminated soil and water for a year or ore by developing extra tough outer coat (mycolic acid)
What is the primary transmission route of M. avium subs. paratuberculosis?
Fecal-oral infection
What is the primary site of infection for M. avium subs. paratuberculosis?
Ileum
How does M. avium subs. paratuberculosis invade?
Through specialized ileal tissue called Peyer’s Patches via M cell to immune cell (macrophage)
What are clinical symptoms of M. avium subs. paratuberculosis?
Persistent diarrhea and weight loss
How is M. avium subs. paratuberculosis diagnosed?
By testing an adult animal
What are the diagnostic tests available for M. avium subs. paratuberculosis that are approved by the USDA?
Fecal culture
ELISA
Gene probe/PCR test
Is there treatment for Johne’s?
No
Should a vaccine be used against M. avium subs. paratuberculosis?
No
What is being done for control and eradication of M. avium subs. paratuberculosis?
USDA sponsored voluntary eradication program
