If we have a 5 gram food sample that was homogenised in sterile Ringer’s solution to give a total volume of 10 cm3. After that, if we serially dilute where 0.1 cm3 aliquots of a number of dilutions are spread plated on duplicate nutrient agar plates, and after incubation, we get for example the following colony counts in dilution 10-3:
Dilution Replicate (1)Replicate (2)
10-3 315 306
I know how to calculate the CFU/cm3 of the homogenate. But, how do we calculate the average CFU/g of food sample?
if 5 grams give 10 cm3, what is the factor to recalculate CFU/cm3 to CFU/g? 🙄
As I understood after asking, after calculating CFU/cm^3. We now say that this is for (5g/10cm^3), that is for 1/2 dilution, but here, we have to find it as a whole and not as a dilution.
So, it will be: result of CFU/cm^3 * 1/0.5 = CFU/g of food sample
