Mycobacteria

    Cards (36)

    • What type of bacteria are mycobacteria?
      Aerobic
    • What shape are mycobacteria?
      Rod-shaped
    • What does it mean for mycobacteria to be acid fast?
      They resist decolorization by acid or alcohol
    • What are acid fast bacilli (AFB)?
      Red, straight or slightly curved rods
    • What contributes to the acid fastness of mycobacteria?
      High content of mycolic acid and lipids
    • What are the main components of the mycobacterial cell wall?
      1. Outer lipids
      2. Mycolic acid
      3. Polysaccharides (arabinogalactan)
      4. Peptidoglycan
      5. Plasma membrane
      6. Lipoarabinomannan (LAM)
      7. Phosphatidylinositol mannoside
      8. Cell wall skeleton
    • Why are mycobacteria difficult to stain using ordinary methods?
      Due to their high lipid content in the cell wall
    • What is the primary stain used in Ziehl-Neelsen staining?
      Carbol fuchsin
    • How is staining enhanced in Ziehl-Neelsen staining?
      By steam heating to melt the wax
    • What is used to decolorize nonacid-fast cells in Ziehl-Neelsen staining?
      20% sulfuric acid
    • What is the purpose of counterstaining in Ziehl-Neelsen staining?
      To provide contrast against red AFB
    • What color do pus cells appear in Ziehl-Neelsen staining?
      Green or blue
    • What is the most significant pathogen for humans in the Mycobacterium tuberculosis complex?
      Mycobacterium tuberculosis
    • What is the primary disease caused by Mycobacterium tuberculosis?
      Tuberculosis (TB)
    • What parts of the body can tuberculosis affect?
      Lungs, bones, joints, brain, kidneys
    • How many people died from TB in 2022?
      1.3 million
    • What is the second leading infectious killer worldwide?
      Tuberculosis (TB)
    • What was the TB case rate in Malaysia in 2022?
      77.8 cases per 100,000 people
    • What are the high-risk groups for tuberculosis?
      • Close contacts with TB patients
      • Immunocompromised patients
      • Substance abusers and smokers
      • People in overcrowded conditions
    • How is Mycobacterium tuberculosis transmitted?
      Through airborne particles called droplet nuclei
    • What factors determine the likelihood of MTB transmission?
      Number of organisms, air concentration, exposure time
    • What is latent TB?
      Infection without active disease or symptoms
    • What are the common symptoms of pulmonary TB (PTB)?
      • Fatigue
      • Weakness
      • Loss of appetite
      • Weight loss
      • Fever
      • Night sweats
      • Chronic cough with sputum
      • Haemoptysis
      • Pleuritic chest pain
      • Dyspnea
    • What investigations are used for PTB?
      • Full Blood Picture (FBP)
      • ESR or C-reactive protein
      • Chest X-ray (CXR)
      • Mantoux test or IGRA
      • Microbiological investigation
    • What is the Mantoux test used for?
      To determine infection with Mycobacterium tuberculosis
    • What is the cut-off value for the Mantoux test?
      Varies by risk group
    • What do Interferon-Gamma Release Assays (IGRA) measure?
      Immune reactivity to M. tuberculosis
    • What are the advantages of IGRA tests?
      • Single patient visit required
      • Results available within 24 hours
      • No false-positive from prior BCG vaccination
    • What are the methods for microbiological investigation of PTB?
      1. Microscopic examination for AFB
      2. Isolation by culture method
      3. Identification tests
      4. Antimycobacterial Susceptibility Testing (AST)
      5. Nucleic acid amplification testing (NAAT)
    • What is the main clinical sample for PTB diagnosis?
      Sputum
    • What is the limitation of microscopic examination for AFB?
      Low sensitivity requiring high bacilli count
    • What are the culture methods for diagnosing tuberculosis?
      • Conventional solid media (e.g., Lowenstein-Jensen)
      • Agar-based media (e.g., Middlebrook 7H10)
      • Liquid/broth media (e.g., Middlebrook 7H9)
    • What is the major constraint of culturing mycobacteria?
      Slow growth requiring at least 4 weeks
    • What are traditional methods for identifying mycobacteria?
      Growth rate, pigment production, colony morphology
    • What are the first-line anti-TB drugs?
      • Rifampicin
      • Isoniazid
      • Pyrazinamide
      • Ethambutol
      • Streptomycin
    • What are the second-line anti-TB drugs?
      • Amikacin
      • Ofloxacin
      • Ciprofloxacin
      • Cycloserine
      • Enviomycin
      • Clarithromycin
      • Azithromycin
      • Para amino salicylic acid
      • Ethionamide
      • Clofazimine