Mycobacterium Tuberculosis

Question 1

Overview/Charcteristics

Answer 1

• Neither Gram positive or Gram negative rods
• non-motile
• non-spore forming
• aerobic
• Rods regularly form branched filaments, but these are disrupted easily
• requires acid fast stain
• grow slow (division time 15-20 hours)
• require special media

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Question 2

Non- M.Tub Species Classfication:
Runyon Group

Answer 2

• Photochromogens: slow growing, produce non-pigmented colonies when grown in the dark and pigmented colonies only after exposure to light and reincubation
  EX: M. kansasii, M. marinum
• Scotochromogens: slow growing, produce deep yellow to orange colonies when grown in the presence of either the light or the dark.
  EX: M. scrofulaceum, M. gordonae
• Non-chromogens: slow growing, non-pigmented in the light and dark or have only a pale yellow, buff or tan pigment that does not intensify after light exposure.
  EX: M. avium, M. ulcerans
• Fast Growing: grow fast (only trait)

Question 3

Mycobacterium Cell Wall

Answer 3

• polysaccharide is lined w/ high-molecular weight mycolic acids.
• The mycolic acid layer is overlaid with a lipids, glycolipids, peptidoglycolipids and proteins
• prevents opzination
• Glycolipids include phosphatidyinositol mannosides (PIM).
• Mannose Capped Lipoarabinomanan (LAM)
• extremely hydrophobic, limiting diffusion of small molecule in the cell
• Stickey
• One reason for poor staining and response to many antibiotics