Microbiology Lab Practical

Microbiology Experiment

• Fomites are inanimate objects that can carry and transmit microorganisms.

Experimental Method

• The experiment involved streaking samples on different types of plates, including environmental and skin/mucous membrane plates.

Observations

• Trends observed during the experiment are not explicitly stated in the provided text.

Hemolysis

• Alpha hemolysis: partial breakdown of red blood cells, resulting in a greenish tint around the colony.
• Beta hemolysis: complete breakdown of red blood cells, resulting in a clear zone around the colony.
• Gamma hemolysis: no breakdown of red blood cells, resulting in no visible change around the colony.

Transmission Modes

• Four modes of transmission:
  • Direct contact: physical contact between an infected individual and a susceptible host.
  • Indirect contact: contact with a contaminated fomite that has been touched by an infected individual.
  • Airborne transmission: transmission through the air, such as through coughing or sneezing.
  • Vector transmission: transmission through an intermediate agent, such as an insect.

Aseptic Technique

• Aseptic technique is used to prevent contamination of microorganisms in laboratory settings
• Key steps include:
  • Flame sterilization of equipment (e.g. loop)
  • Flaming the openings of test tubes to eliminate transient microorganisms
  • Working in a clean and sanitized environment

Flaming Sterilization

• Flame sterilization of a loop involves:
  • Holding the loop in a Bunsen flame until it is red hot
  • Allowing the loop to cool before use

Culture Media

• Broth: a liquid medium used to support microbial growth
• Slant: a solid medium used to support microbial growth, with a sloping surface
• Deep: a solid medium used to support microbial growth, with a deeper layer

Incubation

• Conditions for incubating plates/cultures:
  • In a controlled environment (e.g. temperature, humidity)
  • For a specified period of time (e.g. 24 hours)
• Standard conditions for incubating bacterial cultures:
  • 37°C (98.6°F)
  • Aerobic environment

Microbial Growth

• Cough plate: used to detect airborne microorganisms, showing growth of microorganisms present in the air
• Air plate: used to detect airborne microorganisms, showing growth of microorganisms present in the air

Hemolysis

• Alpha hemolysis: partial breakdown of red blood cells, resulting in a greenish zone around the bacterial colony
• Beta hemolysis: complete breakdown of red blood cells, resulting in a clear zone around the bacterial colony
• Gamma hemolysis: no breakdown of red blood cells, resulting in no visible zone around the bacterial colony

Microscopy

• Good quality smear:
  • Uniformly spread and dried
  • Cells spread evenly and not overlapping
• Basic stains:
  • Positively charged, binding to negatively charged cell components
  • Examples: methylene blue, crystal violet
• Acidic stains:
  • Negatively charged, binding to positively charged cell components
  • Examples: fuchsin, eosin
• Heat fixation:
  • Used to fix cells to a slide, allowing them to adhere and not be washed away
  • Unstained cells are:
    • Cells that have not been stained with a dye

Gram Staining

• Gram stain:
  • Used to differentiate between Gram-positive and Gram-negative bacteria
  • Stains used:
    • Crystal violet
    • Iodine
    • Ethanol
    • Safranin

Fungi

• Dimorphic:
  • Fungi that can exist in two different forms (e.g. yeast and mold)
  • Examples: Candida, Histoplasma
• Hyphae:
  • Long, branching filaments that make up the mycelium
• Mycelium:
  • A mass of hyphae
• Reproduction:
  • Fungi can reproduce by producing spores or by fragmentation

Durham Tubes

• Durham tubes:
  • Used to detect gas production in microbial cultures
  • Contain a small inverted tube that traps any gas produced

Phenol Red

• Phenol red:
  • A pH indicator used to detect changes in pH due to microbial metabolism
  • Turns yellow in acidic conditions and pink in basic conditions

Sugar Fermentation

• Sugars tested:
  • Glucose, lactose, etc.
• Homolactic fermentation:
  • Fermentation that produces only lactic acid as a product
  • Examples: Lactobacillus
• Heterolactic fermentation:
  • Fermentation that produces a mixture of products, including lactic acid, ethanol, and carbon dioxide
  • Examples: Leuconostoc