Thanks so much,.

but when i did formation of biofilm  and the washing three times with PBS and then add the fresh media containing the antibiotic with different concentration and then mad serial dilution to detect MIC of antibiotic that inhibit the growth of bacteria. also there is turbidity in the wells of the  tissue culture plate. what is your suggestion?

Your problem statement is not clear to me. To my concern you first placed any appropriate fibre plate on a culture of Streptococcus canis or you simply grow it in a microliter plate using antibiotic free media,. So at the bottom of plate or over the fibre plate biofilm will grow. Then you have washed it with PBS, then  added the fresh media containing the antibiotic of different concentration. For every concentration of antibiotic turbidity comes. 

Two conclusion may be done

1. Drug donot have any effect over biofilm

2. The drug itself may bring turbidity to to culture Medium. 

So to my suggestion u may check a blank experiment giving culture free medium with particular dose of antbiotic in it. Then compare the UV data...with  medium with added culture with particular dose of antbiotic . 

Thanks so much Anupam Roy