Spread Plate Technique

Theoretical Background / Context

• The spread plate method is used to isolate individual colonies from a diluted sample of the mixed population. 
• Different ways have been developed for the isolation of microorganisms from a mixture sample but among them the Spread plate culture method is the most widely used plating techniques in microbiology in the laboratory.
• An ideal spread plate should contain visible and isolated colonies of bacteria that are evenly distributed in the plate and are countable. 

Importance of Spread Plate:

• In microbiology, the Spread Plate technique with serial dilutions is a vital research tool.
• This technique is used to study the cultural characteristics of the specimen.
• It is used to separate the bacteria in discrete colonies from the sample carrying more than 1 bacterium.
• Used to study the Sensitivity and/or Resistance properties of bacteria against particular Drugs/Antibiotics.
• Used to get sufficient growth of the bacterium for different tests.
• Used to determine the viable numbers of the bacteria in the specimen.
• Spread Plate mythos is used for transportation or short-term storage of the specimen.

Spread Plate Method Principle of Work

• The spread plate technique is a method of isolation in which a diluted microbial sample containing more than one microorganism is deposited on a solidified agar plate and spread uniformly across the surface with an L-shaped glass rod while the media plate is spun on a turntable. 
• With an accurately diluted sample, cells (CFUs) will be deposited far enough individual on the agar surface to grow into individual colonies.
• The main principle behind this Spread Plate technique is that as the Petri dish rotated, at some stage, single cells will be deposited with the bent glass rod onto the agar surface, these cells will be separated from each other by a distance sufficient to allow the colonies that develop to be free from each other as illustrated in the spread plate technique diagram.