Direct counts of cells in liquid samples can be performed using a Petroff-Hausser counting chamber. Research this method and describe how it compares to the viable plate count method of determining the number of CFU in a sample.

The viable plate count is the most commonly used method to estimate the number of viable cells in a sample; while the Petroff-Hausser counting chamber is a direct microscopic count method generally used for counting bacteria and sperm cells.

The Petroff-Hausser counter is a counting chamber used to count microorganisms and cells (e.g., bacteria and spermatic cells) under the microscope. The Petroff-Hausser counter chamber is divided into 25 large squares which are in turn divided by double lines. Moreover, within each large square, there also are 16 small squares divided by single lines. Petroff-Hausser counting chambers are often used to directly determine the number of bacteria in a culture or liquid medium. Petroff-Hausser counting chambers are used to count the number of cells in a given volume of culture liquid by observing 10 to 20 microscope fields. The viable plate count, also known as simply plate count, is the most commonly used procedure to estimate the number of viable cells in a sample. The viable plate count method consists in obtaining serial dilutions of a sample having viable microorganisms/cells which are plated onto a growth medium. This method (viable plate count) can be used to determine the number of actively dividing cells.

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