Well, there might be as much protocols as researchers investigating plasmid satbility !!
What I proprose to you is not the easiest but the more robust approach.
Always proceed from a liquid culture of your transformed bacteria just after transferring them in a non-selective medium (never never from colonies on a solid medium). At regular times, take up an aliquot of this culture and dilute it to get roughly a cell density of about 1000-10000 cells per ml. Spread 100 microliter of this final dilution on a nonselective medium Petri dish (to measure the living cells) and another 100 microlietrs on a selective medium plate (to measure those yet harboring the plasmid). Follow the decay kinetics over hours.
Thank You. I know there are a lot of protocols. I've read several papers in LAB (Lactobacillus and Streptococcus spp.), however, the materials and method section are always short, concise and vague. I really appreciate your response.
I will study, try and get back to you with what I come up with soon.