28-Mycobacteria Flashcards
What is acid-fast staining?
Acid-fast bacteria cannot be decolorized with acid solutions once stained.
With respect to Mycobacteria, the cell wall is rich in lipids, making the surface hydrophobic and thus resistant to many disinfectants and common laboratory stains. Once stained, however, this cell wall also prevents decolorization by acid solutions.
What is the natural reservoir for Mycobacteria?
Humans
M. tuberculosis- epidemiology
Person to person spread by infectious aerosols
M. avium- epidemiology
. Acquired primarily through ingestion of contaminated water or food; inhalation of infectious aerosols is believed to play a minor role in transmission. Patients at greatest risk for disease are those who are immunocompromised
M. leprae- epidemiology
Person-to-person spread is by direct contact or inhalation of infectious aerosols
What type of mycobacteria causes leprosy?
M. leprae
What is tuberculoid leprosy?
• Patients with tuberculoid leprosy (paucibacillary) have a strong cellular immune reaction, with many lymphocytes and granulomas present in the tissue and relatively few bacteria. Tuberculoid leprosy is detected by the body and taken care of.
What is leprmatous leprosy?
• Patients with lepromatous leprosy(multibacillary), however, have a strong antibody response but a specific defect in the cellular response to M. leprae antigens. Thus an abundance of bacteria are typically observed in dermal macrophages and the Schwann cells of the peripheral nerves. As would be expected, this is the most infectious from of leprosy
What media do you use to culture M. tuberculosis?
o Culture on Lowenstein-Jensen and Middlebrook slow growing taking from 10 to 14 days
How can you test pateints for M. tuberculosis?
o Use PPD skin test where 5 tuberculin units of PPD are inoculated into the intradermal layer of the patients skin. Skin test reactivity (defined by the diameter of the area of injection) is measured 48 hours later. If it goes away no for TB for you. Or a CXR.
