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Questions and Answers
What type of immunity is primarily produced by primary TB in immunocompetent people?
What type of immunity is primarily produced by primary TB in immunocompetent people?
Which drug combination is commonly used as first-line agents for treating TB?
Which drug combination is commonly used as first-line agents for treating TB?
What is the potential consequence of not completing the treatment for TB?
What is the potential consequence of not completing the treatment for TB?
What is the primary function of the Bacillus Calmette-Guérin (BCG) vaccine?
What is the primary function of the Bacillus Calmette-Guérin (BCG) vaccine?
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What can occur if a person has latent TB infection?
What can occur if a person has latent TB infection?
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Which cells are responsible for producing IFN-gamma in the context of TB infection?
Which cells are responsible for producing IFN-gamma in the context of TB infection?
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What is a severe complication of Pott's disease or Skeletal TB?
What is a severe complication of Pott's disease or Skeletal TB?
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What is the outcome of effective macrophage-mediated immunity in response to TB?
What is the outcome of effective macrophage-mediated immunity in response to TB?
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What is the main distinguishing feature of Mycobacteria compared to other genera?
What is the main distinguishing feature of Mycobacteria compared to other genera?
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Which species of Mycobacterium is known to grow rapidly on Modified MacConkey Agar?
Which species of Mycobacterium is known to grow rapidly on Modified MacConkey Agar?
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Which of the following Mycobacterium species fails to grow in vitro?
Which of the following Mycobacterium species fails to grow in vitro?
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What characteristic describes most species of Mycobacterium regarding their growth rate?
What characteristic describes most species of Mycobacterium regarding their growth rate?
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Which of the following statements about Mycobacterium tuberculosis is true?
Which of the following statements about Mycobacterium tuberculosis is true?
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What type of bacteria does Mycobacterium marinum belong to?
What type of bacteria does Mycobacterium marinum belong to?
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How long is the typical incubation period for most pathogenic species of Mycobacterium?
How long is the typical incubation period for most pathogenic species of Mycobacterium?
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Which of the following classifications does Mycobacterium belong to?
Which of the following classifications does Mycobacterium belong to?
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What is the primary radiographic view used for the detection of TB-related chest abnormalities?
What is the primary radiographic view used for the detection of TB-related chest abnormalities?
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Which of the following is true regarding BCG (bacille Calmette-Guerin) vaccination?
Which of the following is true regarding BCG (bacille Calmette-Guerin) vaccination?
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What factor can lead to the recurrence of primary TB lesions?
What factor can lead to the recurrence of primary TB lesions?
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What type of radiographic view may be helpful, especially for children when diagnosing TB?
What type of radiographic view may be helpful, especially for children when diagnosing TB?
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In pulmonary TB disease, where are radiographic abnormalities often seen?
In pulmonary TB disease, where are radiographic abnormalities often seen?
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Which of the following describes the characteristics of lesions in pulmonary TB?
Which of the following describes the characteristics of lesions in pulmonary TB?
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How does M. tuberculosis primarily infect the lungs?
How does M. tuberculosis primarily infect the lungs?
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What is an important consideration when interpreting chest radiographs for TB in HIV-infected individuals?
What is an important consideration when interpreting chest radiographs for TB in HIV-infected individuals?
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What is the primary causative agent of Hansen disease (leprosy)?
What is the primary causative agent of Hansen disease (leprosy)?
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Which of the following statements accurately describes tuberculoid leprosy?
Which of the following statements accurately describes tuberculoid leprosy?
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How can Mycobacterium leprae be cultured for research purposes?
How can Mycobacterium leprae be cultured for research purposes?
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What distinguishes lepromatous leprosy from tuberculoid leprosy?
What distinguishes lepromatous leprosy from tuberculoid leprosy?
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What is a common symptom of tuberculoid leprosy?
What is a common symptom of tuberculoid leprosy?
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What categorizes Mycobacteria based on the semiquantitative catalase test?
What categorizes Mycobacteria based on the semiquantitative catalase test?
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A 3+ reaction in the semiquantitative catalase test is characterized by what color?
A 3+ reaction in the semiquantitative catalase test is characterized by what color?
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Which of the following Mycobacterium species is NOT commonly associated with nitroreductase production?
Which of the following Mycobacterium species is NOT commonly associated with nitroreductase production?
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Which factors influence the ability of acid-fast bacilli to reduce nitrate?
Which factors influence the ability of acid-fast bacilli to reduce nitrate?
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How long should slow-growing Mycobacteria be tested for results?
How long should slow-growing Mycobacteria be tested for results?
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What does a control tube in the semiquantitative catalase test indicate if it remains clear?
What does a control tube in the semiquantitative catalase test indicate if it remains clear?
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Which of the following Mycobacterium species can yield a positive result in nitrate reduction?
Which of the following Mycobacterium species can yield a positive result in nitrate reduction?
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What is the reaction time to read the semiquantitative catalase test?
What is the reaction time to read the semiquantitative catalase test?
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Study Notes
Mycobacteria Characteristics
- Mycobacteria are acid-fast due to their cell wall structure, making them distinguishable from other genera.
- Acid-fast bacilli (AFB) are a key characteristic to identify Mycobacteria.
- Mycobacteria are aerobic, but some can grow in reduced oxygen concentrations.
- The majority of Mycobacteria are non-spore-forming, except for Mycobacterium marinum.
- Most Mycobacteria are non-motile, very thin, and slightly curved or straight rods.
- Mycobacteria are generally slow-growing, taking 2-6 weeks for incubation, except for Mycobacterium fortuitum-chelonei which can grow in 3 days on modified MacConkey agar.
- Mycobacterium leprae cannot be grown in vitro using agarose medium.
Mycobacterium Tuberculosis
- Mycobacterium tuberculosis is known as Koch's bacillus or Tubercle bacilli.
- Robert Koch first described Mycobacterium tuberculosis in 1882.
- Mycobacterium tuberculosis primarily infects the lungs, but can also affect other parts of the body, like the kidneys, spine, and brain.
Tuberculosis
- Two distinct conditions exist: Latent tuberculosis infection (infected but not ill) and Tuberculosis disease (active infection leading to illness).
- Chest radiographs are useful for diagnosing tuberculosis disease, with chest abnormalities suggesting pulmonary TB.
- Posterior and anterior radiographs are commonly used to detect TB-related chest abnormalities.
- Lateral radiographs may be helpful in some cases, particularly for children.
- In pulmonary TB, radiographic abnormalities are often found in the apical and posterior segments of the upper lobe, or the superior segments of the lower lobe.
- Lesions can appear anywhere in the lungs and may differ in size, shape, density, and cavitation, especially in HIV-infected or immunosuppressed individuals.
Primary Tuberculosis Pathogenesis
- Alveolar macrophages phagocytize M. tuberculosis cells, allowing for intracellular multiplication.
- Granulomas are formed, and CD4+ T cells produce IFN-gamma, contributing to the immune response.
- Immunocompetent individuals usually control the infection within weeks, and the lesions heal.
- Systemic immunity developed during primary TB offers protection from disseminated infection.
Tuberculosis Treatment
- Latent tuberculosis infection can be treated to prevent progression to disease.
- Tuberculosis disease is treated with a standard 6-month course of antibiotics, sometimes 5 months.
- RIPES (first-line) drugs are commonly used for treatment.
- CCCOKER (second-line) agents are also used in some cases.
- Multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) require more complex treatment regimens.
- TB preventive treatment is given to individuals with TB infection but without active disease to prevent the onset of illness.
- Bacillus Calmette-Guerin (BCG) vaccine is available to help protect against disseminated TB and meningitis, but it is not fully effective against all forms of TB.
Pott's Disease
- Tuberculosis spondylitis is a severe form of musculoskeletal tuberculosis, where the spinal vertebrae are infected.
- Causes bone destruction, deformity, and potential paraplegia.
Mycobacteria Differentiation: Catalase Test
- The catalase test differentiates Mycobacteria based on their catalase enzyme activity.
- Mycobacteria are grouped based on the amount of bubbles produced during the test:
- Less than 45 mm of bubbles
- More than 45 mm of bubbles
- The test includes:
- Tween 80 (a detergent)
- 30% H2O2
- 2-week old culture grown in an agar deep
- The column size is recorded as greater than or less than 45 mm.
Nitrate Reduction Test
- The nitrate reduction test helps identify Mycobacterium kansasii, M. szulgai, M. fortuitum, and M. tuberculosis.
- The test involves the reduction of nitrate to nitrite.
Mycobacterium leprae
- Causes Hansen disease or leprosy, affecting the skin, mucous membranes, and peripheral nerves.
- Cannot be cultivated in vitro, but can be grown in the armadillo and footpads of mice.
- Polymerase Chain Reaction (PCR) assays can detect and identify M. leprae in infectious tissues.
Tuberculoid Leprosy vs. Lepromatous Leprosy
- Tuberculoid leprosy exhibits skin lesions and nerve involvement (loss of sensation) with an effective cell-mediated immune response.
- Lepromatous leprosy presents with skin lesions and progressive, symmetric nerve damage. This form does not produce an effective cell-mediated immune response.
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Description
This quiz covers the key characteristics of mycobacteria, including their unique cell wall structure, growth conditions, and identification methods. It also highlights the significant aspects of Mycobacterium tuberculosis, known for its role in tuberculosis infections. Test your knowledge on these microorganisms!
