What is the Difference Between Pour Plate and Spread Plate?

Pour Plate and Spread Plate are two microbial techniques used to enumerate the number of viable cells present in a sample. The main differences between these two methods are as follows:

• Distribution of Colonies: A spread-plate assay produces a plate with colonies distributed across the agar surface, while a pour plate assay results in a mixture of colonies embedded within the agar layer and colonies presenting at the agar surface.
• Mixing of Sample and Agar: In the pour plate technique, a known volume of the sample is first mixed with agar and then poured into a plate. In the spread plate technique, the sample is spread evenly over the agar surface before it solidifies.
• Accuracy: Pour plate has a higher accuracy than the spread plate when comparing the accuracy of these two techniques.

Despite these differences, both pour plate and spread plate techniques are straightforward methods for counting viable cells in a sample, and both are subject to sampling errors, limitations of growth conditions, and technical errors. Neither method is suitable for growing unculturable bacteria.

Comparative Table: Pour Plate vs Spread Plate

The pour plate and spread plate methods are both techniques used to isolate and count bacterial colonies in a sample. Here is a table comparing the differences between the two methods:

The main difference between the pour plate and spread plate methods is the way the inoculum is combined with the agar. In the pour plate method, molten agar is poured onto the inoculum, while in the spread plate method, the inoculum is spread on the surface of the solidified agar. The pour plate method is generally more accurate than the spread plate method. Both methods require Petri dishes and nutrient agar.