8. Laboratory Findings

Conjunctival Swab

  • Coag(-) staph ® skin contaminant
  • Routine culture sent for mycobacterial work-up
  • AFB smear done

Routine Mycobacterial Cultures

  • Acid fast stain of smear
  • Inoculate Middlebrook 7H11 media
    • Split plate with antibiotics (PACT) on one side
  • Inoculate Lowenstein-Jensen slant
    • Egg based media
    • Malachite green added for bacterial inhibition
  • Inoculate Bactec bottle

Bactec System

  • Radiometric, automated system to detect growth of mycobacteria
    • C14 labeled palmitic acid
    • PANTA added
    • Growth index recorded based on radioactive CO2 production
  • Growth index (>300)
    • Can use DNA probes for rRNA
    • Mycobacterium tuberculosis
    • Mycobacterium gordonae
    • Mycobacterium avium complex
    • Mycobacterium kansasii

Breakpoint #4

  • What are some of the parameters used to classify the different mycobacteria?