What is the procedure for the spread plate technique?

The general procedure for the spread plate technique is described below.

1. Sterilize the work area and ensure all the PPE is equipped.
2. For liquid samples, conduct serial dilutions to achieve a microbial load running from 20-30 CFU/mL. For solid or semisolid samples, dissolve them in a suitable solvent to create suspensions. Typically mixing 1 gram of sample with 9 mL of solvent achieves a concentration of 10^-1 grams/mL
3. Prepare the spreader by sterilizing a glass rod. Dip the rod in 70% ethanol solution and flame it using a Bunsen burner. Ensure the rod cools adequately. 
4. Label the plate with the dilution factor, date, and sample ID

There are two procedures which can be done to spread the samples.

Procedure 1: Spreading with a bent glass or metal rod

1. Open the petri dish lid and carefully dispense 0.1 mL of the diluted sample onto the center of the agar surface using a calibrated pipette or micro pipette
2. Take a sterile bent glass rod and evenly spread the sample across the entire surface of the plate. If using a turntable, gently spin it and place the spreader against the sample. For manual spreading, hold the plate in your dominant hand and move the spreader in circular motions.
3. Cover the plate with its lid, allowing approximately 5 minutes for the sample to be absorbed by the agar. 
4. Place the plate in an inverted position and proceed to incubate it.

Procedure 2: Spreading with glass beads: Copacabana Method

1. Partially lift the petri dish lid using your thumb and index finger, and carefully place 10-12 sterile glass beads inside.
2. Using a calibrated pipette or micro-pipette, dispense 0.1 mL of the diluted sample onto the center of the agar in the petri dish. 
3. Secure the lid and gently shake the plate horizontally to evenly spread the sample across the agar surface using the glass beads. Repeat this motion around 6-7 times.
4. Rotate the plate either clockwise or counterclockwise by 60 degrees and perform another round of horizontal shaking 6-7 times
5. Rotate the plate again in the same direction by 60 degrees and shake the horizontal plate 6-7 times.
6. Let the plate sit upright for 5 minutes to allow the sample to be absorbed by the agar
7. Dispose of the glass beads by placing them in a container with disinfectant (e.g. 10% chlorine bleach or ethanol)
8. Place the plate in an inverted position and incubate it