11 Questions
What is a primary identification characteristic of Mycobacteria?
Rough, raised colonies
Which test for Mycobacteria results in a positive reaction in M.tuberculosis?
Niacin accumulation test
What is the outcome of hydrolysis of Tween 80 by Mycobacteria?
Amber color change
In the iron uptake test, how is the conversion of ferric ammonium citrate by Mycobacteria indicated?
Rusty brown colonies
How is a positive result in the urease test for Mycobacterium species indicated?
Pink color change
What feature of mycobacteria's cell wall makes them resistant to Gram staining?
Presence of mycolic acid
Which stain is commonly used to visualize mycobacteria under the microscope?
Acid-fast stain
What is the most common mycobacterium causing tuberculosis globally?
Mycobacterium tuberculosis
Which type of media is commonly used for mycobacterial culture and contains casein hydrosolid for drug susceptibility testing?
7H11 agar
What is typically the treatment regimen for tuberculosis involving isoniazid and rifampin?
9 months of isoniazid and rifampin
Which type of media is used for subculturing stock strains of mycobacteria?
H9 broth
Study Notes
- Mycobacteria have a unique cell wall composed of mycolic acid, making them acid-fast bacilli (AFB) and resistant to Gram staining.
- Staining methods for mycobacteria include acid-fast stain, Kinyoun stain, and the Ziehl-Neelsen stain.
- Mycobacteria are aerobic and can be enhanced by exposure to 5-10% CO2.
- Mycobacterium tuberculosis is the most common mycobacterium worldwide, causing tuberculosis (TB).
- TB can affect various organs and can disseminate in individuals with weakened immune systems.
- TB can be diagnosed through culture and sensitivity testing, with treatment typically involving 9 months of isoniazid and rifampin.
- Mycobacterium bovis is another significant human pathogen, transmitted from animals to humans.
- Non-tuberculosis mycobacteria include slow-growing and rapid-growing types, with various species causing infections in humans.
- Laboratory diagnosis of mycobacteria involves collecting specimens like sputum, bronchial washings, urine, and tissue samples for acid-fast bacilli staining and culture.
- Culture media such as Lowenstein-Jensen, Petragnani, and American Thoracic Society media are commonly used for mycobacterial culture.- 7H11 agar contains 0.1% casein hydrosolid to improve recovery of isoniazid resistant strain of Mycobacterium tuberculosis, making it preferred for drug susceptibility testing.
- Liquid media like MGIT is used to propagate bacteria for stock culture, while H9 broth is used for subculturing stock strains.
- Primary identification of Mycobacteria includes rough, raised colonies and cord growth pattern, indicating tuberculosis.
- Biochemical tests for Mycobacteria include niacin accumulation test (positive in M. tuberculosis), nitrate reduction test (positive in M. tuberculosis), and catalase test (positive in all Mycobacteria).
- Hydrolysis of Tween 80 by Mycobacteria releases oleic acid and polyoxyethylated sorbitol, turning neutral red indicator amber in color.
- Iron uptake test challenges Mycobacteria to convert ferric ammonium citrate to iron oxide, seen as rusty brown colonies.
- Arylsulfatase test detects enzyme activity within 3 or 14 days, causing a pH change indicated by pink color.
- Urease test distinguishes Mycobacterium species based on pink (positive) or white (negative) color change in the medium.
Test your knowledge on the unique characteristics of mycobacteria, staining methods, common species like Mycobacterium tuberculosis and Mycobacterium bovis, laboratory diagnosis techniques, and culture media used for mycobacterial culture.
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