microbiology lab midterm #3

• Thermal death time

  Length required to kill all bacteria
• Thermal death point (TDP)

  Temperature required to kill all bacteria in 10 min
• Decimal reduction time (DRT)


  Time (in min) to kill 90% of the population of bacteria
• Optimal growth ranges


  • Psychrophilic: (0-20ºC)
  • Psychrotrophic: (20-30ºC)
  • Mesophiles: (25-40ºC)
  • Thermophiles: (45-65ºC)
  • Hyperthermophiles: (80 or greater)
• Radiant energy spectrum


  The range of all types of electromagnetic (EM) radiation
• UVC range


  • 200-290nm
• The UVC range is harmful to bacteria
• Use-dilution test


  Analyzing the efficiency of disinfectants
• Minimum inhibitory concentration (MIC)


  Minimum concentration of an antimicrobial agent that will inhibit visible growth of a microorganism
• Antibiotics


  Substances produced by a microorganism that inhibits another microorganism
• Antibiotics come from microorganisms
• Disk-diffusion method


  Used to detect the effectiveness of antibiotics on an organism, determined by the zone of inhibition clearing
• Common microorganisms found in skin microbe

  • Staphylococcus
  • Corynebacterium
  • Propionibacterium
• Characteristics of S. aureus

  • Golden yellow halo
  • Coagulase-pos
  • Catalase-pos
• How to test for coagulase

  Place rehydrated coagulase plasma on slide, add a small drop of water, and add culture
• Coagulase test results


  • Positive: clumping
  • Negative: no clumping