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What is the morphology of Mycobacterium in the light microscope?
Slender/Slightly curved/Straight rod shaped
What is the oxygen requirement for Mycobacterium to grow?
Obligate aerobe
How long does Mycobacterium usually grow on complex media?
2-6 weeks
What type of Mycobacterium doesn't grow in vitro?
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How long does rapid Mycobacterium grow on simple media and at what temperature?
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What organisms are part of the Mycobacterium Tuberculosis Complex?
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What organism is associated with TB in tropical Africa?
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What organism is linked with TB among immunocompetent and immunocompromised individuals?
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What organism is primarily found in cattle but can infect other animals and humans?
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What organism causes infections in children and patients with HIV in Africa?
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Who discovered M. tuberculosis?
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Is TB one of the oldest communicable diseases?
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Where does TB usually infect?
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How does TB infect or what is the mode of transmission?
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How does M. tuberculosis evade phagocytosis?
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In a person with adequate cellular immunity, what do macrophages secrete to enhance the inflammatory response?
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What do macrophages secrete at the infection site to destroy intracellular bacteria?
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What type of hypersensitivity does Mycobacterium activate?
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Does the PPD Skin Test imply recent infection of M. tuberculosis?
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Can tuberculosis be reactivated to an active TB?
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In chronic disease of TB, what diagnostic tests confirm tuberculosis?
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What do you call tuberculosis that seeds to other organs?
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What is the order of occurrence when TB infects/invades other organs?
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How does AFB/Mycobacteria spread to these organs?
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Who is mostly infected with Miliary TB?
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What type of Miliary TB infects the kidney and genital organs?
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What type of Miliary TB manifests as typical UTI and sterile pyuria?
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What is the other term for Skeletal TB?
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How does tuberculosis infect the meninges?
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What are the primary drugs for pulmonary tuberculosis?
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What type of vaccine is Bacille Calmette-Guerin (BCG)?
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What other specimens can Mycobacteria be detected in?
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Is delay in processing specimens for Mycobacteria advisable?
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What is the recommended specimen for sputum and other respiratory secretions?
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What interval should be used in detecting Mycobacteria?
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Is 2 of 3 positive sputum smears sufficient for confirmation of diagnosis?
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What specimen is recommended for children and patients who cannot form sputum?
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Is processing of 12-24 hours of pooled specimen recommended for testing Mycobacteria?
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Should stool specimens be frozen if not processed within a few hours of collection?
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What is the amount of specimens recommended for culture in CSF?
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What medium is used for heavily contaminated specimens for Mycobacterium tuberculosis testing?
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What solid medium is most widely employed for routine culture?
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What type of medium do Mycobacteria spp. grow rapidly in?
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What dyes are used for fluorescence microscopy of smears?
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Study Notes
Mycobacterium Morphology
- Mycobacterium is a genus of bacteria that is characterized by its slender, slightly curved, or straight rod-shaped morphology.
Mycobacterium Growth Requirements
- Mycobacterium species are obligate aerobes, meaning they require oxygen to grow.
- The growth of most Mycobacterium species takes 2-6 weeks on complex media.
- Mycobacterium leprae, however, does not grow in vitro.
- Some Mycobacterium species, considered rapid growers, can grow in 2-3 days on simple media at a temperature between 20-40°C.
Mycobacterium Tuberculosis Complex
- The Mycobacterium Tuberculosis Complex (MTBC) consists of several species, including: M. tuberculosis, M. bovis, M. microti, M. africanum, M. canettii, M. pinnipedii, M. mungi, and M. orygis.
- M. africanum is associated with tuberculosis in tropical Africa.
- M. microti is linked with tuberculosis in both immunocompetent and immunocompromised individuals.
- M. bovis is primarily found in cattle but can infect other animals and humans.
- M. canettii causes infections in children and HIV-positive patients in Africa.
Mycobacterium Tuberculosis and Robert Koch
- Robert Koch discovered M. tuberculosis.
- Tuberculosis is one of the oldest communicable diseases.
Tuberculosis Infection
- Tuberculosis primarily infects the respiratory tract.
- Transmission occurs through inhalation of airborne droplets containing tubercle bacilli.
- M. tuberculosis evades phagocytosis due to its thick lipid cell wall, which resists the acidic environment and enzymatic conditions that kill most bacteria.
Immune Response to Tuberculosis
- In individuals with adequate cellular immunity, macrophages secrete IL-12 and TNF to enhance the inflammatory response.
- IFN-gamma, also secreted by macrophages, helps destroy intracellular bacteria.
- Mycobacterium infection triggers type IV hypersensitivity.
Tuberculosis Diagnosis
- A positive PPD skin test indicates past infection with M. tuberculosis, not a recent infection.
- Tuberculosis can reactivate into active TB.
- Stained smears and sputum cultures are diagnostic tests for chronic tuberculosis.
- Miliary tuberculosis occurs when tuberculosis spreads to other organs.
- The order of organ involvement in miliary tuberculosis is spleen, liver, bone marrow, kidney, and adrenal gland.
- Miliary tuberculosis spreads hematogenously.
- Children and individuals with HIV are more prone to miliary tuberculosis.
- Genitourinary tuberculosis, which affects kidneys and genital organs, can manifest as typical urinary tract infections and sterile pyuria (renal TB).
Skeletal Tuberculosis
- Skeletal tuberculosis is also known as Pott's Disease.
Meningitis Due to Tuberculosis
- Tuberculosis can infect the meninges through the rupture of a tubercle into the subarachnoid space.
Tuberculosis Treatment
- The primary drugs for pulmonary tuberculosis are rifampin, isoniazid, pyrazinamide, and ethambutol.
BCG Vaccine
- Bacille Calmette-Guerin (BCG) is a live attenuated vaccine derived from M. bovis.
Sample Collection for Mycobacteria
- Mycobacteria can be detected in urine, feces, blood, cerebrospinal fluid (CSF), tissue biopsies, and aspirates from various tissues.
- Delaying specimen processing for Mycobacteria can lead to false-negative results and bacterial contamination.
- Early-morning specimens are recommended for sputum and other respiratory secretions.
- Three consecutive days of specimen collection is recommended for detecting Mycobacteria.
- Two positive sputum smears out of three are sufficient to confirm diagnosis. If only one smear is positive, additional specimens are needed.
- Gastric aspirates and washings are recommended for children and patients unable to produce sputum.
- Pooled specimens should not be processed for Mycobacteria after 12-24 hours as they are contaminated and may contain few viable tubercle bacilli.
- Stool specimens should be frozen if not processed within a few hours of collection.
- 2 mL of CSF is recommended for culture.
Culture Media for Mycobacteria
- Petragani medium is used for heavily contaminated specimens for M. tuberculosis testing.
- Lowenstein-Jensen (L-J) medium is the most widely used solid medium for routine culture.
- Mycobacteria species grow rapidly on liquid media.
Fluorescence Microscopy
- Auramine phenol and auramine rhodamine dyes are used for fluorescence microscopy of smears.
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