Mycobacterium spp. - Muller Flashcards
What shape is mycobacterium?
Rod shaped
What stain is used for mycobacterium?
Ziehl nielson - mycolic acid in cell wall will stain pink
Mycobacterium is cytochemically gram _______
positive
True or False: Mycobacterium is motile
FALSE - non motile
What structure of mycobacterium is hydrophobic and resistant to adverse environmental influences?
Lipid rich cell wall
Pathogenic species of mycobacterium grows ___________
SLOWLY!
Are diseases in domestic animals acute or chronic?
Chronic and progressive
What are the major diseases from mycobacterium?
- Tuberculosis
- Johne’s disease
- Feline leprosy
What are the main hosts of m. tuberculosis?
Humans + captive primates
What species are infected by m. tuberculosis?
Dogs, cattle, birds
What species are infected by m. bovis?
Deer, badgers, possums, cats, other mammals, HUMANS (zoonotic)
What species can be infected by m. avium?
Pigs, cattle
What species can be infected by m. lepraemurium?
Cats (from rats and mice)
What species can be infected by m. avium subsp. paratuberculosis?
Ruminants (from other ruminants)
Which mycobacterium causes Johne’s disease?
m. avium subsp. paratuberculosis
What are the main hosts of m. avium subsp. paratuberculosis?
Cattle, sheep, goats, deer (ruminants)
Which mycobacterium causes rat leprosy or feline leprosy?
m. lepraemurium
Which species of mycobacterium is slowest to grow on culture?
m. avium subsp. paratuberculosis
Which species of mycobacterium requires a higher temperature than the rest to grow on culture?
M. avium requires 37-43 °C
** others require 37 °C
Which species of mycobacterium is most significant in causing infection in humans?
m. tuberculosis
Which species of mycobacterium requires a growth supplement to grow on culture media? Name the growth supplement it needs.
m. avium subsp. paratuberculosis
Needs Mycobactin to grow!!!
How does staining appear on giemsa for mycobacterium?
Negative staining - cell wall appears clear/doesnt stain
How does staining appear on ZN for mycobacterium?
Cell wall stains pink!
_______ grow fast on culture media
Saprophytes (non pathogenic spp.)
________ improved the isolation time of mycobacterium growth
Liquid culture (rather than solid)
Known as BACTEC
__________ is an important zoonosis in non-industrialized countries
Bovine TB
What environment allows growth of mycobacterium spp. and why?
Cold, dark, moist conditions
** bc of lipids + mycolic acid in cell wall
Who is the main reservoir for m. tuberculosis?
Humans!
True or False: m. tuberculosis can be transfered from animal to human, and from human to animal
TRUEEE
Zoonosis and antropozoonosis
What symptoms are seen in humans with m. tuberculosis and m. bovis?
- Fever
- Night sweats
- Cough
- Bloody phlegm
- Chest pain/ shortness of breath
True or False: bovine TB is reportable and zoonotic
TRUEEE
True or False: M. tuberculosis is reportable
TRUE
What are the reservoirs for m. bovis in the UK and ireland?
Badgers
What are the reservoirs for m. bovis in new zealand?
Opossum
What are the reservoirs for m. bovis in michigan?
White tailed deer
How are cattle infected with m. bovis?
- Aerosol (needs fewer than 10 organisms to spread) * MOST COMMON
- Ingestion (milk) - calves at risk
- Asymptomatic carriers
How are humans infected with m. bovis?
- Ingestion of unpasteurised dairy or undercooked meat
- Aerosol (less common)
- Breaks in the skin
- Person to person: immunosuppressed
How are cats infected by m. bovis?
- Ingestion (drinking milk)
- Aerosol
- Bites and scratches
How are pigs, ferrets, and deer infected by m. bovis?
Ingestion
How are badgers infected with m. bovis?
Bites and scratches
What is the virulence factor in mycobacterium that allows it to cause disease
lipid cell wall allows it to survive and multiple in host macrophages
How does m. bovis cause disease in the host?
-Survives and multiplies in host macrophages
- lipid cell wall blocks phagosome-lysosome fusion which prevents killing of the bacteria
-macrophages recruit T lymphocytes, if they can’t kill bacteria a chronic granulomatous inflammation and a tubercle forms with a central necrotic core
**Delayed type IV hypersensitivity
What is the consistency of the central caseous necrosis?
Cheesy
How can you diagnose Bovine TB in live cattle?
Tuberculin skin test (Cellular response)
- First do preliminary Caudal fold test
- If thickness and swelling from caudal fold test, confirm with a second test: Comparative cervical skin test
- If bovine PPD is higher than avian PPD it confirms positive bovine TB
How can you diagnose bovine TB in cervids?
Single cervical test
What could a false negative PPD test mean?
- Recently infected, tested too soon before 30 days
- Anergy due to advanced TB (tested too late)
- Transient desensitization
- Immunosuppression
What could a false positive result on PPD test mean?
Sensitization to mycobacteria other than m. bovis
** retest comparative cervical test
What is the preliminary screening test used for cattle with TB?
Caudal fold test
1 TB positive cow means ______ are subclinical
1:7
How can bovine TB be controlled?
- Decrease interaction with wildlife and cattle
- Rodent control
- Test and slaughter
- Disinfect using moist heat of 121 °C for min of 15 mins (high heat)
- Disinfect with 5% phenol, iodine solutions, glutaraldehyde and formaldehyde
Transmission of avian TB?
Fecal oral route, excreted in feces of birds
At port mortem, where can you see granulomatous lesions from avian TB?
Liver, spleen, bone marrow, intestines
How can you diagnose avian TB in live animals?
Avian PPD tuberculin injected into the skin of the wattle
How are pigs infected with avian TB?
Ingestion of uncooked swill
** small tubercles in lymph nodes
What clinical signs are associated with cattle positive for m. avium subsp paratuberculosis (MAP)?
Persistant diarrhea, weight loss, eventually death , decreased milk yield
Between dairy herd and beef herds, who is more at risk for MAP?
Dairy herds
How is MAP transmitted?
Excreted in feces, infection via fecal oral route
** also from feeding pooled colostrum (affects young)
Who is more at risk for MAP, a suckling calf or a 3 year old heifer?
Suckling calf - resistance to infection increases with age
Which mycobacterium spp is associated with chronic granulomatous enteritis?
MAP/ Johne’s dz
True or False: when young calves are infected with MAP, clinical signs can always be seen
FALSE - does not show CS, can appear healthy for months to years
What happens as MAP progresses?
- More severe diarrhea
- Further weight loss
- Coat color fades
- Ventral + intermandibular edema due to protein loosing enteropathy
- Emaciation + death
True or False: in sheep, goats, and other ruminants, diarrhea is always seen with MAP
FALSE - diarrhea may not be seen
What pathologic lesions are seen in Johne’s disease?
- Thickened and corrugated intestine
- Enlarged lymph nodes
- Diffuse granulomatous enteritis with epithelioid macrophages on histo
How can you diagnose MAP in live animals?
Pinch biopsies from rectum or from fecal sample
How can you detect MAP post mortem?
- Tissues from lymph nodes and intestines
- direct acid fast stain
-BACTEC liquid culture - PCR
**CANT USE PPD TEST FOR MAP
How can MAP be controlled?
- Seperate calves from dam (mom) at birth
- Raise calves on pasteurized milk
- Isolate calves from the herd for 2 years (until they build resistance)
- Disinfection
- Remove source of MAP (calf feed, water, bedding)
Which species of mycobacterium is NOT zoonotic?
m. lepraemurium
Transmission route for m. lepraemurium?
bites from infected rodents
** cat eating a rat or mouse
Where would you look for lesions on a cat infected with m. lepraemurium?
Head or limbs
What is the definitive test for m. lepraemurium and why?
PCR!! bc m. lepraemurium can’t grow in culture
