The method of specimen preparation depends on:
• The condition of the specimen: living or preserved
• The aims of the observer:
• Observation
• Identification
• Movement
• The type of microscopy available
Wet Mounts or Hanging Drop Mounts
• Cells are suspended in a suitable fluid: water, broth, or saline
• Fluid maintains viability and provides a medium for movement
• Provide a true assessment of size, shape, arrangement, color, and motility of cells
Wet Mounts
• Consist of a drop or two of culture placed on a slide overlaid with a coverslip
• Advantages: quick and easy to prepare
• Disadvantages:
• Can damage larger cells
• Susceptible to drying
• Can contaminate the handler’s fingers
Hanging Drop Mounts
• Prepared with concave (depression) slide, Vaseline adhesive or sealant, and a coverslip
• Overcomes the disadvantages of wet mounts
Fixed, Stained Smears
Smear technique:
• Spread a thin film made from a liquid suspension of cells on a slide
• Allow the slide to air dry
Fixing Smears
• Heat fixing:
• Heat the slide gently after it has been air dried
• Important functions of heat fixing:
• Kills the cells
• Secures the specimen to the slide
• Preserves cellular components in a natural state with minimal distortion
• Alcohol and formalin can also be used for fixation
Staining Smears
• Provides contrast
• Makes inconspicuous features stand out
• Dyes impart colors to cells by becoming affixed to them through a chemical reaction
• Dyes used in microbial staining:
• Basic (cationic): have a positive charge, attracted to acidic, negatively charged
• The condition of the specimen: living or preserved
• The aims of the observer:
• Observation
• Identification
• Movement
• The type of microscopy available
Wet Mounts or Hanging Drop Mounts
• Cells are suspended in a suitable fluid: water, broth, or saline
• Fluid maintains viability and provides a medium for movement
• Provide a true assessment of size, shape, arrangement, color, and motility of cells
Wet Mounts
• Consist of a drop or two of culture placed on a slide overlaid with a coverslip
• Advantages: quick and easy to prepare
• Disadvantages:
• Can damage larger cells
• Susceptible to drying
• Can contaminate the handler’s fingers
Hanging Drop Mounts
• Prepared with concave (depression) slide, Vaseline adhesive or sealant, and a coverslip
• Overcomes the disadvantages of wet mounts
Fixed, Stained Smears
Smear technique:
• Spread a thin film made from a liquid suspension of cells on a slide
• Allow the slide to air dry
Fixing Smears
• Heat fixing:
• Heat the slide gently after it has been air dried
• Important functions of heat fixing:
• Kills the cells
• Secures the specimen to the slide
• Preserves cellular components in a natural state with minimal distortion
• Alcohol and formalin can also be used for fixation
Staining Smears
• Provides contrast
• Makes inconspicuous features stand out
• Dyes impart colors to cells by becoming affixed to them through a chemical reaction
• Dyes used in microbial staining:
• Basic (cationic): have a positive charge, attracted to acidic, negatively charged
