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What is the morphology of Mycobacterium in the light microscope?
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?
What is the oxygen requirement for Mycobacterium to grow?
Obligate aerobe
How long does Mycobacterium usually grow on complex media?
How long does Mycobacterium usually grow on complex media?
2-6 weeks
What type of Mycobacterium doesn't grow in vitro?
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?
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?
What organisms are part of the Mycobacterium Tuberculosis Complex?
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What organism is associated with TB in tropical Africa?
What organism is associated with TB in tropical Africa?
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What organism is linked with TB among immunocompetent and immunocompromised individuals?
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?
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?
What organism causes infections in children and patients with HIV in Africa?
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Who discovered M. tuberculosis?
Who discovered M. tuberculosis?
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Is TB one of the oldest communicable diseases?
Is TB one of the oldest communicable diseases?
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Where does TB usually infect?
Where does TB usually infect?
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How does TB infect or what is the mode of transmission?
How does TB infect or what is the mode of transmission?
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How does M. tuberculosis evade phagocytosis?
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?
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?
What do macrophages secrete at the infection site to destroy intracellular bacteria?
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What type of hypersensitivity does Mycobacterium activate?
What type of hypersensitivity does Mycobacterium activate?
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Does the PPD Skin Test imply recent infection of M. tuberculosis?
Does the PPD Skin Test imply recent infection of M. tuberculosis?
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Can tuberculosis be reactivated to an active TB?
Can tuberculosis be reactivated to an active TB?
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In chronic disease of TB, what diagnostic tests confirm tuberculosis?
In chronic disease of TB, what diagnostic tests confirm tuberculosis?
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What do you call tuberculosis that seeds to other organs?
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?
What is the order of occurrence when TB infects/invades other organs?
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How does AFB/Mycobacteria spread to these organs?
How does AFB/Mycobacteria spread to these organs?
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Who is mostly infected with Miliary TB?
Who is mostly infected with Miliary TB?
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What type of Miliary TB infects the kidney and genital organs?
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?
What type of Miliary TB manifests as typical UTI and sterile pyuria?
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What is the other term for Skeletal TB?
What is the other term for Skeletal TB?
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How does tuberculosis infect the meninges?
How does tuberculosis infect the meninges?
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What are the primary drugs for pulmonary tuberculosis?
What are the primary drugs for pulmonary tuberculosis?
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What type of vaccine is Bacille Calmette-Guerin (BCG)?
What type of vaccine is Bacille Calmette-Guerin (BCG)?
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What other specimens can Mycobacteria be detected in?
What other specimens can Mycobacteria be detected in?
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Is delay in processing specimens for Mycobacteria advisable?
Is delay in processing specimens for Mycobacteria advisable?
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What is the recommended specimen for sputum and other respiratory secretions?
What is the recommended specimen for sputum and other respiratory secretions?
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What interval should be used in detecting Mycobacteria?
What interval should be used in detecting Mycobacteria?
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Is 2 of 3 positive sputum smears sufficient for confirmation of diagnosis?
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?
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?
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?
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?
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?
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?
What solid medium is most widely employed for routine culture?
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What type of medium do Mycobacteria spp. grow rapidly in?
What type of medium do Mycobacteria spp. grow rapidly in?
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What dyes are used for fluorescence microscopy of smears?
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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