Briefly explain the technique of serial dilution to estimate bacterial concentrations.

This technique allows to achieve two objectives: the isolation of the colonies and the count of the microorganisms that are had in the initial culture.

Explanation:

There are five tubes with physiological serum, one of them with 10 mL and the others with 9 mL. With a sterile pipette, 1 mL of the mixed culture is taken and placed in the first tube. Stir until you have a homogeneous suspension. Another pipette is taken and from the first tube 0.1 mL is transferred to the second tube, stirred and the operation is repeated transferring 1mL of the second to the third tube, etc. Once the dilution bank is available, an amount of 0.1 mL in nutrient agar plates is seeded from the last three tubes, using the extension sowing technique. It is incubated at 37°C for 24 hours and the colonies are counted.