Unit 12

What does 'viable count' refer to?

• The number of individual organisms in a sample

• The number of colonies on a plate

• The number of metabolically active cells

• The number of CFUs in a sample

Which technique is used for direct (viable) plate counting?

• Serial Dilution

• Pour Plate

• Spread Plate

• Overcrowded Plates

What is the main precaution to be taken with plate count technique?

• Count only plates with between 30 and 300 colonies

• Count all plates regardless of colony count

• Count only plates with over 300 colonies

• Count only plates with less than 30 colonies

What does TNTC stand for in plate count technique?

• Too Numerous To Count

• Total Number of Colony Units

• Too Numerous To Calculate

• Total Number of Cell Units

What is the purpose of serial dilution in viability studies?

• To increase the concentration of microorganisms

• To reduce the concentration of microorganisms

• To count the number of colonies on a plate

• To calculate the number of CFUs in a sample

How can the number of organisms in the original inoculum be calculated?

• By counting the number of colonies on the plate

• By correcting the number of colonies based on dilution

• By counting the number of CFUs on the plate

• By multiplying the dilution factor with the number of colonies

In Example 1, how many cells/ml of the sample were there in the original tube?

• 610 cells/ml

• 61 cells/ml

• 6.10 x 10^3 cells/ml

• 1 x 10^-1 cells/ml

In Example 2, how many CFUs/ml were there in the original sample?

• 150 CFUs/ml

• 1.5 x 10^8 CFUs/ml

• 1 x 10^-6 CFUs/ml

• 1 x 10^6 CFUs/ml

In Example 3, what is the dilution in the last test tube?

• 1/10

• 1/100

• 1/1000

• 1/10000

In Example 3, how many CFUs are there per ml in the original sample?

• 1 x 10^3 CFUs/ml

• 1 x 10^4 CFUs/ml

• 1 x 10^5 CFUs/ml

• 1 x 10^6 CFUs/ml