I working on bacteriocins production from lactic acid bacteria and I ready for any thing

If you want to just qualitatively determine if the probiotic has got anti-bacterial activity against the pathogen, you could try the cross streak method.

It is a plate assay in which on day 1 a single line streak of the probiotic is made, and allowed to incubate for 24-48 hrs. After which aseptically, the pathogenic bacteria is to be streaked across it, without touching the probiotic colonies.

This is to be further incubated for 24-48 hours. If there is any anti bacterial activity, you can observe a small zone of inhibition near the areas wherein the two organisms cross over.

Co-culture on a liquid media is a little tricky as both organisms may  have population doubling times, and results may be inaccurate due to this.

you may study competition between the probiotic and the pathogen. Is your probiotic a bacteriocin producer? Is there some nutrient competition between the probiotic and the pathogen? Is the probiotic able to reduce the growth of the pathogen and/or the production of some virulence factors?

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I have done some work with Lactobacillus reuteri - producing the antimicrobial reuterin - and Salmonella Typhimurium. I combined both probiotic and pathogen in a 3-D model of the colon epithelium to study the potential of L. reuteri to inhibit Salmonella adhesion, invasion and intracellular growth in the epithelial model.

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Dear colleague,

In this paper, we demonstrate the inhibition potential of LAB against S. aureus invasion in a cell culture model.

Hope it can help you.

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