1. MOST PROBABLE NUMBER (MPN) METHOD
statistical method
usually higher counts than SPC
masses of glassware
no colony morphology
replicate tubes inoculated with dilutions (3-5 replicates)
growth in tube shown by some form of change in media
eg turbidity / gas production
Positive tubes refer to MPN tables to give MPN/g
Can be used with any selective media for enumeration

2. Flow chart of Presumptive MPN

3. Flow chart of Confirmed and Completed MPN

5. MPN tables refer to Australian Standard 1766. 1
MPN tables refer to Australian Standard Estimation of Most Probable Number of Microorganisms Tables 1 and 2