Mycobacterium Flashcards
doesn't contain Mycobacterium avium's pathogenesis
Identify the bacteria:
★ strictly aerobic, non-spore forming, gram (+) rods
★ rods or cocci
★ acid-fast
Mycobacterium
Lipid content of cell wall is how many % of Mycobacterium’s dry weight?
60%
What is responsible for Mycobacterium’s hydrophobicity, slow growth, and its resistance to acids, disinfectants, antibodies, and desiccation?
Lipid content of cell wall
What are the 2 substances in Mycobacterium’s lipid?
mycolic acid
trehalose 6, 6’ dimycolate (cord factor)
This classification system is based on growth rate and pigment production
Runyon’s Classification
Group 1 Mycobacterium
Photochromogenic Strains
Group 2 Mycobacterium
Scotochromogenic Strains
Group 3 Mycobacterium
Non-chromogenic strains
Group 4 Mycobacterium
Rapid growers
This group of Mycobacterium grow slowly, produce yellow pigment when exposed to light, produce skin ulcers and pulmonary diseases in humans
Group 1: Photochromogenic Strains
This group of Mycobacterium grow slowly, form orange-yellow pigment whether grown in light or dark, considered saprophyte
Group 2: Scotochromogenic Strains
This group of Mycobacterium grow slowly, do not produce pigments, form smooth colonies, resistant to isoniazid, highly pleomorphic, produce filaments resembling Nocardia, cause pulmonary diseases in humans
Group 3: Non-chromogenic strains
This group of Mycobacterium grow rapidly, mature in less than 1 week at 25-37C
Group 4: Rapid growers
Mycobacteria could also be grouped as…? (3)
SOF
1.) saprophytes
2.) obligate parasites
3.) facultative intracellular parasites
What are the important different Mycobacteria spp. that cause diseases in domestic animals? (5)
TAP FB
1.) M. avium
2.) M. tuberculosis
3.) M. paratuberculosis
4.) M. farcinogenes
5.) M. bovis
Mycobacteria that causes disease in avians
M. avium
Mycobacteria that causes disease in humans, primates, dogs, pigs, cattle
M. tuberculosis
Mycobacteria that causes Johne’s disease, debilitating disease in cattle characterized by chronic/intermittent diarrhea
M. paratuberculosis
Mycobacteria that causes bovine farcy (tropical countries)
M. farcinogenes
Mycobacteria that causes tuberculosis in cattle, pig, cat, horses, primates, dogs, sheep; pathogenic for humans
M. bovis
Mycobacteria morphology
short, plump rods in tissues; large, slender, and beaded in culture media; acid-fast
Most frequently used media to culture Mycobacteria (incorporated with egg yolk) (2)
Dorset’s Egg Medium
Stonebrink’s Medium
Inhibitory substance of mediums used to culture Mycobacteria
(technically, it should be “carbon source” not “inhibitory”)
Glycerol
Primary culture of Mycobacteria requires _-_weeks at __C before colonies are detected
6-8 weeks at 37C
colonies appearance of Mycobacteria
minute dull flakes that thicken into dry irregular masses
rough and wavy; thick and wrinkled in fluid medium
pigment/color of colonies of Mycobacteria
light yellow that progresses into deep yellow to brick red if exposed to light
growth and elevation of colonies of Mycobacteria
confluent growth on surface; limited to surface unless wetting agents added
Wetting agent added in media used for cultivation of Mycobacteria
Tween 80
Antigens of Mycobacteria that makes up its cell wall (3)
MWC (GMT)
1.) Mycosides (glycolipids)
2.) Waxes D (mycolic acid)
3.) Cord factor (trehalose 6,6 dimycolate)
Antigen of Mycobacteria that is a protein/polypeptide released in the medium
Tubercuoprotein or Tuberculin
Principal route of transmission of Mycobacteria (4)
SCAM
1.) Sexual
2.) Congenital
3.) Aerogenous
4.) Milk borne
Natural primary host of Mycobacteria
Cattle
Do Mycobacteria have toxins / extracellular virulence factor? Yes or No?
No
Cord factor present in virulent strains is important in stimulating what?
Granulomatous responses
Pathogenesis of Mycobacteria (10)
IA AMRF IBDB
1.) inhale
2.) alveolar sac
3.) alveolar macrophages
4.) multiplies & kills phagocytes
5.) reingested by macrophages
6.) filtered from regional lymphatic system
7.) intracellular multiplication
8.) bloodstream
9.) disseminated to other body sites
10.) back to lungs
Cell’s ability to prevent fusion of lysosome and phagosome, prevents intracellular digestion. This is called what?
Anti-fusion Effect
Primary site of Mycobacteria
Tubercles form (macrophages, lymphocytes, other leukocytes)
Sites of secondary metastasis of Mycobacteria (translucent pearly structures like small grains of tapioca)
Regional lymph nodes
As growth of tubercles continues, necrosis occurs at the centers, pearls become yellow-white opaque then there is fusion/continued growth of macrophages, what are these?
Giant cells of Langhans
Central part of necrotic lesions consists of very dry, cheesy material contains what?
Ca deposits surrounded by dense connective tissue
Lesions in the anterior lobes
Caseocalcareous lesions
Difficult to demonstrate in old lesions
Tubercle bacilli
Large masses of smooth, grape-like bodies on serous surfaces
Tuberculous pleuritis/peritonitis
In what animal are lesions caused by Mycobacteria can be found in lymph nodes of head, neck, abdomen?
Swine
In what animal are lesions caused by Mycobacteria can be found in pharyngeal region, mesentery, lungs, liver, spleen?
Horse
In what animals are lesions caused by Mycobacteria mainly pulmonary and progressive in young kids?
Sheep and Goat
In what animal are lesions caused by Mycobacteria can be found in abdominal organs and lungs?
Cat
Cell-mediated immune response is
effective for how many weeks after infection?
4 weeks
Diagnosis of Mycobacteria infection (4)
1.) characteristic lesion (necropsy)
2.) Ziehl-Neelsen’s staining
3.) culture, isolation, identification
4.) animal inoculation
5.) tuberculin test (M. tuberculosis & M. bovis)
What mediums can be used to culture, isolate, & identify Mycobacteria in diagnosis? (2)
Lowenstein-Jensen medium
Kirchner medium
M. tuberculosis is more potent but less specific than M. bovis. True or False?
True
Common sites for intradermal injection for Tuberculin Test (3)
Caudal fold
Lip of vulva
Side of the neck (most sensitive)
After injection in Tuberculin Test, reaction is examined after how many hours?
72 hours
Vaccine made from a weakened strain of M. bovis which provide protection against tuberculosis, particularly in countries where M. tuberculosis is endemic
BCG (Bacillus Calmette-Guérin)
Other methods of Tuberculin Test (3)
Ophthalmic Test
Thermal Test
Stormont Test
Involves two injections of tuberculin at same site; reaction is examined after 7 days
Stormont Test
Runyon’s classification under Group 3, morphology is more variable in shape than M. bovis, strongly acid & alcohol fast,
Mycobacterium avium
Mycobacterium avium cultural growth and colony appearance
less than 1 week, well developed in 2 weeks
colonies are soft, moist, yellow that becomes yellowish to pinkish with age and exposure to light
Antigens of Mycobacterium avium (3)
1.) M. intracellulare complex of serotypes 1-21
2.) serotypes 1-2 (chicken & avian)
3.) serotype 3 (cattle)
Immunity of Mycobacterium avium
cell mediated and humoral
On what medium is Mycobacterium avium isolated on for diagnosis?
Dorset’s medium
