Which of the following is an advantage of the standard plate count?
A provides immediate results
B determines the number of viable cells
C can readily count cells that form aggregates
D it can get results easily from cells that are crowed.
The correct answer and explanation is :
The correct answer is B: determines the number of viable cells.
Explanation:
The standard plate count method, also known as the viable plate count or colony count method, is widely used to determine the number of viable microorganisms (such as bacteria) in a sample. The key advantage of this method is its ability to determine the number of living, metabolically active cells in the sample, which can reproduce and form colonies under the right conditions.
Here’s how the standard plate count works: A sample of the microbial population is serially diluted and then plated onto an agar medium. The plates are incubated for a specific period, typically 24 to 48 hours. During this time, viable bacteria will grow and form visible colonies. After incubation, the number of colonies is counted, and this count is used to calculate the concentration of viable organisms in the original sample.
This method specifically counts viable cells, which are cells capable of growing and reproducing under favorable conditions. This is important because the standard plate count only includes living cells, which are the ones that have the potential to cause infections or spoil products. It doesn’t count dead cells or those that are not actively dividing, which could give an inaccurate estimate of the actual microbial activity in a sample.
Now, let’s examine the other choices:
- A: provides immediate results: This is incorrect. The standard plate count does not provide immediate results because it requires incubation to allow microbial colonies to grow, which typically takes 24-48 hours.
- C: can readily count cells that form aggregates: This is also incorrect. The standard plate count method may struggle with counting cells that form aggregates or clumps because those aggregates might not separate into individual colonies, potentially leading to an underestimation of the microbial population.
- D: it can get results easily from cells that are crowded: This is incorrect as well. Crowded cells may not grow into individual colonies due to competition for nutrients and space on the agar surface, complicating the counting process.
In conclusion, the standard plate count is advantageous because it accurately counts viable cells that can reproduce, making it a reliable method for assessing microbial contamination in various samples.