I’ve a standard microorganisms, what is the ideal method to dissolve the disc in diluent (how much of diluent ?) for making a serial dilution to have 100 cfu or less for growth promotion test ? and how long time it will be kept in refrigerator ?
Dissolve the disk in sufficient volume to make the solution and make serial dilution to find the desire solution to get about 100 cfu/ml. Read it in detail.
Use mcfarland standarts.
Use 0,5 mcfarland for bacteria and 2mcf for fungi and molds
2 mcf and 0,5mcf gives you 1.5*100.000.000 colonies but you must validate that dilution counts for each microorganisms.
When you dilute the microorganisms use two SCDA and two SDA plates for test each microorganism suspension counts. (Dont forget to vortex the suspensions before dilutions)
Than you can use the suspensions for various tests like growth promotion or method validations.
thank you sir
I made all these steps, but unfortunately i haven’t the device to measure the mcf of turbidity for solutions.