Chapter 2 Flashcards
(22 cards)
What are the members of the genus Mycobacterium?
M. Tb complex (africanum, microti, bovis), saprophytic mycobacterium, non-tuberculous mycobacterium, mycobacterium leprae, and BCG.
Mention some of the properties of M. Tuberculosis.
- slowly growing, acid fast bacilli
- Culture must be held for 6 to 8 weeks before being recorded as negative.
- culture can be done on bacteriologic culture like LJM which has egg yolk and malachite green to inhibit the normal flora in a sputum culture.
- they are obligate aerobes that cause disease in highly oxygenated areas like the upper lobe of the lung.
- their acid fastness is due to mycolic acid in the cell wall.
What are the substances of the cell wall that are correlated with disease production in m. tb?
- mycolic acid: causes the acid fastness
- cord factor: correlated with virulence.
- sulfolipids: inhibit phagolysosome fusion.
- several proteins which when combined with waxes elicit delayed hypersensitivity reaction.
What are the proteins in MTB cell wall used for?
These proteins are the purified protein derivatives in the tuberculin test.
The high lipid content of the cell wall in MTB has been associated with several properties. State them. Hint: ARRS.
Acid fastness, resistance to antibiotics, resistance to acidic and alkaline compounds, survival inside macrophages.
What are the routes of infection with MTB/M.Bovis?
MTB is transmitted from person to person through respiratory aerosol and the organism resides within reticuloendothelial cells (macrophages).
M. Bovis causes gastrointestinal tuberculosis and the route of infection is drinking contaminated unpasteurized milk.
There are two types of lesions in MTB infection.
Exudative or Granulomatous.
Patients are tuberculin positive in latent tuberculous infection. Yes or No?
Yes.
Primary tuberculosis usually occurs in the lower lobes of the lung. Yes or No?
Yes.
What are the symptoms of tuberculosis?
Fever, fatigue, night sweats, hemoptysis, cough and weight loss
Sputum smears are negative in latent tb infection. Yes or No?
Yes.
All types of tuberculosis infection usually occur in the lower lobes of the lung. Yes or No?
No. Reactivation lesions usually occur in the apices of the lung.
Where is the initial site of spread after infection with MTB?
Regional lymph nodes.
What happens when tuberculous bacilli reach the blood stream?
Miliary distribution occurs.
What’s scrofula?
Mycobacterial cervical lymphadenitis which occur after ingestion of contaminated milk with m. bovis.
What’s the most common extrapulmonary manifestation of tuberculosis?
Lymphadenitis.
What parts of the vertebral column are most affected by tb in Pott’s disease?
Lower thoracic and upper lumbar vertebrae.
What are the most characteristic finding in renal tuberculosis?
Sterile pyuria.
Dysuria, hematuria and flank pain also occur.
What’s the gold standard for diagnosis of MTB?
Culture.
What’s the alternative for ZNS that is used for rapid screening purposes?
Auramine stain which is visualized by fluorescence microscopy.
M. Tuberculosis produces a substance and reduces another. State them.
Produces niacin and reduces nitrate.
There are two approaches for diagnosis of latent tb infection. State.
Tuberculin test or IGRA
