Mycobacteria Flashcards
What are the major characteristics of mycobacteria?
- relatively slow growth rate
- acid fast staining
- aerobic
- nonmotile
- non spore forming
Cell wall of mycobacterium tuberculosis
Over 60% lipid -> mycolic acid, cord factor, wax-D
Mycolic acids in virulence
- hydrophobicity of cell wall
- decreased permeability
- inhibition of macrophage activation
- disruption of phagosome-lysosome complex
- granuloma formation
What kind of inflammatory disease is caused by M. Tuberculosis?
Granulomatous inflammatory disease
Are there toxins in M. Tuberculosis?
No
2 stages of Tuberculosis
- TB infection/ latent TB
- active TB/ TB disease
What is the gold standard in lab identification of m. Tuberculosis?
Culture
What are the possible cultures for Mycobacteria and what is the content?
Egg based media
-> Lowenstein Jensen ->Egg, Potato, Glycerol, Malachite green
-> Petragnani
Semisythetic media
-> middlebrook
Staining methods of Mycobacterium
Acid fast staining -> Ziehl neelsen (hot stain)
-> Kinyoun (cold stain)
Fluorochrome stain -> Auramine rhodamine
Acid fast (Kinyoun) Stain of Mycobacterium
Cord growth of virulent strains
Ziehl Neelsen (acid-fast) stain of Mycobaterium
M. Tuberculosis
Acid fast stain
Pink strains -> M. Tbc
Blue -> polymorphonucleae leukocytes, other cells inside the specimen
Cord factor of Tuberculosis
Classification of MOTT
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)
What is leprosy?
A chronic granulomatous disease of the peripheral nerves and superficial tissues
2 forms of leprosy
- tuberculoid -> lesions large spots, lepromin test positive, strong immune response
- lepramatous -> extensive nodules, destruction of skin, lepromin test negative, low immune response
Actinomyces characteristics
- anaerobic
- slow growth
- normal inhabitants of GIS
Chronic suppurative and granulomatous disease is caused by
Actinomycosis
How is the clinical specimen containing pus observed in Actinomycosis?
Small, firm usually yellowish particles, no sulfur
The most common species of Actinomyces in clinical infections
A. Israelii
Staining of actinomyces
Gram stain
What is observed in gram staines smears prepared from lesions in actinomyces?
Characteristic sulfur granules
Clinical materials in actinomycosis infections should be inoculated in which medium?
Thioglycollate medium
What are Actinomyces producing during growth?
Branching filaments
What are the characteristics of nocardia?
- branching of the bacterial cells
- partial acid fastness
- exogenous infections
- aerobic
Nocardia species
- N. Asteroides -> opportunistic lung & CNS infections
- N. Braziliensis -> pathogen of skin & subuct. Tissue
