Mycobacterium

What are the key characteristics of the genus Mycobacterium?

Strictly aerobic, non-spore forming, curved or straight

Gram (+) rods (acid fast organism)

Forms___________that break into ______ or_____i when

disturbed

Filaments, rods, and cocci

How does the high lipid content (60% of dry weight) in the cell wall of Mycobacterium affect its properties and growth?

It makes Mycobacterium hydrophobic, slows its growth, and increases resistance to acids, disinfectants, antibiotics, and desiccation

It categorizes nontuberculous mycobacteria (NTM) based on their growth rate and pigment production.

Runyon’s Classification

What are the four classification under Runyon’s Classification

• Group I – Photochromogenic strains

• Group 2 – Scotochromogenic strains

• Group 3 – Non-chromogenic strains (No pigment production)

• Group 4 - rapid grower

Which group in Runyon’s classification grows slowly, produces a yellow pigment when exposed to light, and causes skin ulcers and pulmonary diseases in humans?

Group I – Photochromogenic strains

Which group in Runyon’s classification grows slowly, forms an orange-yellow pigment in both light and dark, and is usually considered saprophytic?

Group 2 – Scotochromogenic strains

Which group in Runyon’s classification grows slowly, does not produce pigments, forms smooth colonies resistant to isoniazid, is highly pleomorphic with filamentous forms resembling Nocardia, and causes pulmonary diseases in humans?

Group 3 – Non-chromogenic strains

Which group in Runyon’s classification consists of rapid growers that mature in less than one week at 25 to 37°C?

Group 4 – Rapid growers

Which Mycobacterium species is pathogenic for humans and is found in meat and milk?

Mycobacterium bovis

Which Mycobacterium species causes Johne’s disease in cattle?

Mycobacterium paratuberculosis

Which Mycobacterium species is commonly found in eggs and meat?

Mycobacterium avium

Which Mycobacterium species causes bovine farcy in tropical countries?

Mycobacterium farcinogenes

Which Mycobacterium species affects humans, primates, dogs, pigs, and cattle?

Mycobacterium tuberculosis

Most frequently used media in Mycobacterium?

Dorset’s, Stonebrink’s w/ egg yolk

How many week does Mycobacterium spp does needed?

Usually 6-8 weeks, depends on the species

What is the appearances of colonies Mycobacterium in media?

Colonies appear minute dull flakes, progressing into dry irregular masses

Mycobacterium color changes from light yellow to ______/____ upon light exposure

deep yellow/brick red

In fluid medium, we used _____ to separate the organism?

Tween 80

Which part of the bacteria does antigens found in mycobacterium?

Cell wall, which composed of 3 lipids

What are the three lipids found in the cell wall of mycobacterium?

mycosides (glycolipids), waxes D (mycolic acid), cord factor (trehalose 6,6 dimycolate)

Which component released into the medium by Mycobacterium tuberculosis is used for diagnostic testing?

Tubercuoprotein/Tuberculin

What are the principal modes of transmission for Mycobacterium infections?

• Aerogenous (Airborne)

• Milkborne

• Congenital (Primary complex in young animals)/sexually transmitted

What is the natural primary host of the Mycobacterium?

Cattle

What is unique about Mycobacterium tuberculosis in terms of toxin production and extracellular virulence factors?

It produces no toxins or extracellular virulence factors.

How does Mycobacterium evade intracellular digestion by immune cells?

It prevents lysosome-phagosome fusion, inhibiting intracellular digestion (antifusion effect).

How does Mycobacterium tuberculosis infection progress in the body?

Tubercles (aggregates of macrophages, lymphocytes, and leukocytes) form at the primary infection site, then spread to lymph nodes and metastasized sites.

What are the common sites of Mycobacterium lesions in swine?

Lymph nodes of the head, neck, and abdomen

What are the common sites of Mycobacterium lesions in horses?

Pharyngeal region, mesentery, lungs, liver, and spleen

What are the common sites of Mycobacterium lesions in sheep and goats?

Mainly pulmonary, progressive in young kids

What are the common sites of Mycobacterium lesions in cats?

Abdominal organs and lungs

How are macrophages activated in response to Mycobacterium infection?

lymphokines from T-lymphocytes

Does immunity completely eliminate Mycobacterium from the body?

No, some organisms remain

How long do T-lymphocytes remain sensitized after infection?

For life

What staining method we used to identify the capsule of Mycobacterium?

Ziehl-Neelsen staining, which is a acid fast staining

What are the characteristic lesions found at necropsy in Mycobacterium infections?

Primary lesions in the lungs

This test was used to “identify the species of Mycobacterium” using animals?

Animal inoculation

What are the three animals that we used in animal inculcation?

Guinea pig, Rabbit, and chicken

Result from animal inoculation (Guinea pig (+), Rabbit (+/-), Chicken (0) which species of mycobacterium is most likely is involved?

M. tuberculosis

Result from animal inoculation (Guinea pig (+), Rabbit (+), Chicken (0) which species of mycobacterium is most likely is involved?

M. bovis

Result from animal inoculation Guinea pig (+/-), Rabbit (+), Chicken (+) which species of mycobacterium is most likely is involved?

M. avium

Which test we used for mycobacterium to test the potency of bacteria?

Tuberculin test

Where are the site of injection for Tuberculin test?

Caudal fold, lip of vulva, side of the neck

Among the three site of injection (Caudal fold, lip of vulva, side of the neck)? which one is more sensitive?

side of the neck

What is the comparative test used to differentiate between avian and mammalian Mycobacterium?

Comparative tuberculin test

What does BCG stand for in Mycobacterium diagnostics?

Bacillus of Calmette and Guérin

What are some diagnostic tests used for Mycobacterium infections?

Ophthalmic test, thermal test, and Stormont test

What is the procedure for the Stormont test?

Two injections, examined 7 days later

Which Runyon’s classification does M. avium belong?

Runyon’s Group 3

What are the colony characteristics of Mycobacterium avium?

Soft, moist, yellow, turning pinkish with age and light exposure

What are the morphological characteristics of Mycobacterium avium?

Highly variable, strongly acid-fast, and alcohol-fast

What serotype is present in M. avium especially in chicken ?

Serotype 1 & 2

How many serotypes are included in the Mycobacterium intracellulare complex?

Serotypes 1-21

What is the natural host of Mycobacterium avium?

Birds

Which serotypes of Mycobacterium avium are virulent for chickens?

Serotypes 1, 2, and 3

How does avian tuberculosis progress in birds?

Slow progression, rare in birds younger than 1 year

What are the characteristic lesions of avian tuberculosis?

Caseous lesions in the intestines, liver, and spleen

What is the impact of Mycobacterium avium on cattle?

Minimal lesions but sensitizes to avian/mammalian tuberculin

How does Mycobacterium avium affect swine?

Lesions in mandibular and mesenteric lymph nodes

What types of immunity are involved in Mycobacterium avium infections?

Both cell-mediated and humoral immunity

What are the diagnostic methods for Mycobacterium avium?

Ziehl-Neelsen staining