VPE 511: Environment and Environmental Hygiene (2+1)

SAMPLING

• Liquid Impringement Method
  • Sterile distilled water or nutrient broth is taken in a dish or tube and exposed to air in the required area for 15 min.
  • The distilled water or broth is then inoculated onto agar plates which are in turn incubated for 24 hours at 37⁰C.
• Filtration
  • Air may be filtered using various fillters such as paper, membrane, inorganic fibre filter, sand, etc. Air is allowed to pass through the glass tube containing sand.
  • A negative pressure is created inside the tube. The sand is then inoculated into nutrient medium and observed for growth.
• Electrostatic precipitation
  • A petridish coated with nutrient medium is subjected to electric current of 2000V. This attracts the suspended microbes to the plate.
  • The plates are incubated and observed for growth. 
• Centrifugation Method
  • Here a centrifugal force is created to deposit particles in air on the required medium. The agar plates are then incubated and observed for growth.