Mycobacteria

Question 1

What are the major characteristics of mycobacteria?

Answer 1

• relatively slow growth rate
• acid fast staining
• aerobic
• nonmotile
• non spore forming

Question 2

Cell wall of mycobacterium tuberculosis

Answer 2

Over 60% lipid -> mycolic acid, cord factor, wax-D

Question 3

Mycolic acids in virulence

Answer 3

• hydrophobicity of cell wall
• decreased permeability
• inhibition of macrophage activation
• disruption of phagosome-lysosome complex
• granuloma formation

Question 4

What kind of inflammatory disease is caused by M. Tuberculosis?

Answer 4

Granulomatous inflammatory disease

Question 5

Are there toxins in M. Tuberculosis?

Answer 5

No

Question 6

2 stages of Tuberculosis

Answer 6

• TB infection/ latent TB
• active TB/ TB disease

Question 7

What is the gold standard in lab identification of m. Tuberculosis?

Answer 7

Culture

Question 8

What are the possible cultures for Mycobacteria and what is the content?

Answer 8

Egg based media
-> Lowenstein Jensen ->Egg, Potato, Glycerol, Malachite green
-> Petragnani

Semisythetic media
-> middlebrook

Question 9

Staining methods of Mycobacterium

Answer 9

Acid fast staining -> Ziehl neelsen (hot stain)
-> Kinyoun (cold stain)

Fluorochrome stain -> Auramine rhodamine

Question 10

Answer 10

Acid fast (Kinyoun) Stain of Mycobacterium
Cord growth of virulent strains

Question 11

Answer 11

Ziehl Neelsen (acid-fast) stain of Mycobaterium

Question 12

Answer 12

M. Tuberculosis
Acid fast stain
Pink strains -> M. Tbc
Blue -> polymorphonucleae leukocytes, other cells inside the specimen

Question 13

Answer 13

Cord factor of Tuberculosis

Question 14

Classification of MOTT

Answer 14

Photochromogens -> yellow orange pigment on culture if exposed to light -> M. Kansasii

Serotochromogens -> yellow orange pigments on culture under any condition -> M. Scrofulaceum

Nonchromogens -> no pigment -> M. Avium intracellulare (common opportunistic infection in AIDS Patients)

Question 15

What is leprosy?

Answer 15

A chronic granulomatous disease of the peripheral nerves and superficial tissues

Question 16

2 forms of leprosy

Answer 16

• tuberculoid -> lesions large spots, lepromin test positive, strong immune response
• lepramatous -> extensive nodules, destruction of skin, lepromin test negative, low immune response

Question 17

Actinomyces characteristics

Answer 17

• anaerobic
• slow growth
• normal inhabitants of GIS

Question 18

Chronic suppurative and granulomatous disease is caused by

Answer 18

Actinomycosis

Question 19

How is the clinical specimen containing pus observed in Actinomycosis?

Answer 19

Small, firm usually yellowish particles, no sulfur

Question 20

The most common species of Actinomyces in clinical infections

Answer 20

A. Israelii

Question 21

Staining of actinomyces

Answer 21

Gram stain

Question 22

What is observed in gram staines smears prepared from lesions in actinomyces?

Answer 22

Characteristic sulfur granules

Question 23

Clinical materials in actinomycosis infections should be inoculated in which medium?

Answer 23

Thioglycollate medium

Question 24

What are Actinomyces producing during growth?

Answer 24

Branching filaments

Question 25

What are the characteristics of nocardia?

Answer 25

• branching of the bacterial cells
• partial acid fastness
• exogenous infections
• aerobic

Question 26

Nocardia species

Answer 26

• N. Asteroides -> opportunistic lung & CNS infections
• N. Braziliensis -> pathogen of skin & subuct. Tissue