Card Set Information

2013-05-27 21:16:28
Clinically Important Mycobacterium

Clinically Important Mycobacterium
Show Answers:

  1. What clinical conditions are associated with Mycobacterium tuberculosis?
    Tuberculosis (chronic, primarily lower respiratory tract disease)
  2. How is Mycobacterium tuberculosis spread?
    Person-to-person via infected droplets, dust, etc.
  3. Describe the pathology of Primary tuberculosis
    • Infection begins in the midle or lower areas of the lungs
    • Bacteria can spread to lymphatic system, CNS, and heart
    • Macrophages phagocytize the bacteria and form multinucleated cells, which are eventually surrounded by fibroid cells - forming tubercles (seen on x-rays)
    • If the tubercles calcify - they are called ghon complexes
  4. When the mycobacterium tuberculosis is contained withing the granulomas (called tubercles) what is the stage of the disease called?
    Latent infection
  5. Describe the why Reactivation or Secondary tuberculosis of Mycobacterium tuberculosis occurs
    • Occurs in people with latent TB
    • Can be triggered by poor nutrition, alcoholism, or hormonal factors associated with pregnancy and diabetes
  6. Describe the treatment of the Reactivation or secondary tuberculosis
    • Long term combination therapy - can last up to 24 months
    • First line drugs include isoniazid, rifampin, ethambutol, and pyrazinamide
  7. Describe Multidrug-resistant Mycobacterium tuberculosis (MDR-TB)
    • Simultaneous resistance to isoniazid and rifampin
    • 1st discovered in 1991
    • If present, it indicates a poor prognosis
  8. Describe Extremely-drug resistant Mycobacterium tuberculosis (XDR-TB)
    • Resistance to any fluoroquinolone, and at least one of 3 injectable second-line drugs (capreomycin, kanamycin, and amikacin)
    • In addition, to resistance to isoniazid and rifampicin
  9. Describe the Purified protein derivative (PPD) test
    • Skin test to determine exposure to mycobacterium tuberculosis
    • Antigen is composed of heat-killed, filtered, ammonium sulfate precipitated  protein from mycobacterium tuberculosis
    • Injected intradermally and examined at 48 hours for swelling (induration)
    • A positive skin test indicates previous exposure to the bacteria but not necessarily active disease
  10. What is the test called that is the skin test that determines exposure to mycobacterium tuberculosis?
    Purified protein derivative (PPD)
  11. What mycobacteria has the tests and results:
    Colony morphology on LJ media - nonpigmented (tan or buff), dry, heaped, and granular in 14-21 days at 37 degrees celcius
    Acid-fast stain often shows ropelike formations (cording) from broth culture
    Niacin POS
    Nitrate POS
    p-nitro-alpha-acetylamino-beta-hydroxypropiophenone (NAP) susceptible
    Mycobacterium tuberculosis
  12. What clinical condition is associated with Mycobacterium leprae?
    Hansen disease (leprosy)
  13. What mycobacteria:
    Clinical condition: Hansen disease (leprosy)
    Based on characteristics skin lesions
    Visualizing AFB in lesions
    Cannot be grown on artificial media
    Mycobacterium leprae
  14. What 2 species are grouped together in the Mycobacterium avium complex (MAC)?
    • Mycobacterium avium
    • Mycobacterium intracellulare
  15. What clinical conditions are associated with Mycobacterium avium complex (MAC)?
    • Disseminated disease in immunosuppressed patients with human immunodeficiency virus infections
    • Lung infections
    • Lympadenitis
    • Intestinal infections
  16. What is a specific trait of Mycobacterium avium complex (MAC)?
    Slowly growing nonchromogens
  17. What mycobacteria has the tests and results:
    Clinical conditions: Pulmonary infections, Causes lung disease that resembles classic TB - rarely disseminates except in patients with severe immunosuppression
    Slow grower
    Nitrate POS
    Catalase POS
    Most commonly isolated photochromogen in the US and isolated from tap water around the world
    Mycobacterium kansasii
  18. What mycobacteria:
    Clinical conditions: Cervical lympadenitis, Other types of infections predominantly in children
    Slowly growing scotochromogen
    Mycobacterium scrofulaceum
  19. What have Mycobacterium ulcerans, marinum, and haemophillium all been clinically associated with?
    • Skin infections
    • They have a predilection for surface areas and extremities of the body is related to their optimal growth temp of 30-32 degrees celcius
  20. What special nutrients are needed for the growth of Mycobacterium haemophilium?
    • Ferric ammonium citrate OR hemin
    • Can be grown on Chocolate agar
  21. What mycobacteria has the tests and results:
    Clinical conditions: Zoonosis, Pulmonary infections
    Nitrate NEG
    Niacin NEG
    T2H sensitive
    Mycobacterium bovis
  22. What are Mycobacterium fortuitum, chelonnae, and abscessus clinically associated with?
    • Abcesses
    • Osteomyelitis
    • Wound infections
    • Lung infections
    • Weakly virulent
  23. What Mycobateria are rapid growers?
    • Mycobacterium fortuitum
    • Mycobacterium chelonae
    • Mycobacterium abscessus
  24. What Mycobateria is often isolated as a contaminate and a slow growing scotochromogen?
    Mycobacterium gordonae
  25. What clinical conditions are associated with Mycobacteria?
    • Tuberculosis
    • Other diseases
  26. Generally these results identifies what?
    Acid-fast bacilli
    Non-spore forming
    Obligate Aerobes
    Heat sensitive catalase
    Semiquantitative catalase
    Growth on MAC
    Nucleic acid assays (AccuProbe, Strip assays, Direct nucleic acid amplification)
  27. How do you ID Mycobacteria under a microscope?
    • Acid-fast stain
    • Ziehl-Neelsen stain requires heating during the staining step
    • Kinyoun's stain does NOT require heating during the staining step
    • (Do NOT use Gram Stain because it the lipids in their wall will prevent penetration of crystal violet and safranin)
  28. What is the primary stain in Acid-fast?
    Carbol fuchsin
  29. What specimens are Mycobacteria found in?
    • Lower respiratory tract - sputums, bronch wash
    • Urine
    • Blood
    • Bone marrow
    • Tissue
    • Body fluids
  30. How would you perform digestion and decontamination of sputum samples?
    • 2% NaOH with N-acetyl-L-cysteine (NALC)
    • NaOH increases the pH to a level that is antibacterial
    • NALC is a mucolytic agent that liquefies mucus
  31. What samples require digestion and decontamination procedures for mycobacteria?
    Only specimens containing normal flora - like sputums that contain bacteria from the oral cavity
  32. What solid media is used when dealing with Mycobacteria?
    • Lowenstein-Jensen (LJ)
    • Lowenstein-Jensen-Gruft
    • Middlebrook medium (this media generally exhibits growth several days before egg-based media, antimicrobials can be added to make the media selective for mycobacteria)
  33. What liquid media is used when dealing with Mycobacteria?
    • Middlebrook 7H9 broth (used to maintain stock cultures and prepare isolates for biochemical tests)
    • Mycobacterium growth index tube (MGIT) (mycobacteria will consume oxygen and the fluorchrome will fluoresce when exposed to UV light)
    • BACTEC 460TB system (contains a radioactively labeled substrate that is metabolized by mycobateria)
  34. What groups are the members of mycobacteria are placed in and why?
    • Runyon groups
    • Placed into groups according to their growth rate and photoreactivity
  35. As far as growth rate, which growers of Mycobacteria are associated to be pathogenic?
    • Slow growers
    • (Rapid growers take approx. a week to grow)
  36. What are the Photoreactivity results for Mycobacteria?
    • Photochromogens - yellow to orange pigment only when exposed to light
    • Scotochromogens - yellow to orange pigment in light and in the dark
    • Nonchromogens (nonpigmented) - do not produce pigment
  37. Describe the Mycobacteria members of the Runyon group 1
    • Slow growers
    • Photochromogens
  38. Describe the Mycobacteria members of Runyon group 2
    • Slow growers
    • Scotochromogens
  39. Describe the Mycobacteria members of Runyon group 3
    • Slow growers
    • Nonchromogens
  40. Describe the Mycobacteria members of group 4
    Rapid growers
  41. What mycobacteria has the tests and results:
    Heat-sensitive catalase - NEG
    Semiquantitative catalase - production of a column of bubbles <45 mm
    Nitrate reductase POS
    Niacin POS
    ID with AccuProbeID with Direct nucleic acid amplification
    Mycobacteria tuberculosis
  42. What mycobacteria has the tests and results:
    Heat-sensitive catalase NEG
    Nitrate reductase NEG
    Susceptibility to thiophene-2-carboxylic acid hydrazide (T2H)
    Mycobacteria bovis
  43. What mycobacteria has the tests and results:
    Nitrate reductase POS
    ID with AccuProbe
    Mycobacteria kansasii
  44. What are the Mycobacteria that will grow on a MAC plate in 5 days?
    • Mycobacteria fortuitum
    • Mycobacteria chelonei
  45. What species of Mycobacteria are Nitrate reductase POS?
    • Mycobacteria tuberculosis
    • Mycobacteria kansasii
    • (Most others are NEG)