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21.1: Learning Objectives

  • Page ID
    40288
  • Learning Objectives

    After this lab you should be able to:

    1. Perform an Acid-Fast Stain on a mixed culture of bacteria (Acid-Fast/non-Acid-Fast).
    2. Explain the principles of how the Acid-Fast Stain works.
    3. Evaluate and interpret your Acid-Fast Stain results correctly.
    4. Interpret and troubleshoot poor stain results.
    clipboard_e2bcb9e9b342b590ba0d66bbb0431a986.png
    Figure \(\PageIndex{1}\): Acid-Fast Stain of Mycobacterium smegmatis, 1000x Kelly Carrillo Burke CC-CY-NC-SA

    “Tuberculosis (TB) is one of the world’s deadliest diseases:

    • One third of the world’s population is infected with TB.
    • In 2014, 9.6 million people around the world became sick with TB disease. There were 1.5 million TB-related deaths worldwide.
    • TB is a leading killer of people who are HIV infected.

    A total of 9,421 TB cases (a rate of 2.96 cases per 100,000 persons) were reported in the United States in 2014. Both the number of TB cases reported and the case rate decreased; this represents a 1.5% and 2.2% decline, respectively, compared to 2013. This is the smallest decline in more than a decade.”1

    “The presence of acid-fast-bacilli (AFB) on a sputum smear or other specimen often indicates TB disease. Acid-fast microscopy is easy and quick, but it does not confirm a diagnosis of TB because some acid-fast-bacilli are not  M. tuberculosis. Therefore, a culture is done on all initial samples to confirm the diagnosis. (However, a positive culture is not always necessary to begin or continue treatment for TB.) A positive culture for M. tuberculosis  confirms the diagnosis of TB disease. Culture examinations should be completed on all specimens, regardless of AFB smear results. Laboratories should report positive results on smears and cultures within 24 hours by telephone or fax to the primary health care provider and to the state or local TB control program, as required by law.”2

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