Once I tried Streptococcus MIB determination by growth in agar plates with different concentrations of the tested compound. But I did not tested for inhibitory effect, only bactericidal 

Hi Waleed Younis,

MIC

You can determine the antimicrobial activity (MIC) of the antibiotics using the well diffusion method against your different pathogenic strains. The pathogenic strains spread on the surface of the media petri plates containing Muller–Hinton agar with 0.1 ml of previously prepared microbial suspensions individually containing 1.5 × 108 cfu ml−1 (equal to 0.5 McFarland).  Prepare 6.0 mm diameter wells in the media plates using a cork borer, and add the antibiotics at a dose range of 125–0.9 μg per well. The plates were incubate for 24 h at optimum temperature (optimum temp for your organism) .The well containing the least concentration showing the inhibition zone was considered as that with the minimum inhibitory concentration.

MBIC

Take overnight cultured pathogens in tryptone soy broth (supplemented with 0.5% glucose) and the antibiotics of predetermined concentrations ranging from 0 to 250 μg ml−1 mix with the bacterial suspensions having an initial inoculum concentration of 5 × 105 CFU ml−1. Distribute the aliquots of 100 μl in each well (96 well plate) and then incubate at 37 °C for 24 h under static conditions. Discard the medium and then wash with phosphate buffered saline to remove the non-adherent bacteria. Each well of the microtiter plate was stained with 100 μl of 0.1% crystal violet solution followed by 30 min incubation at room temperature. Later discard the crystal violet solution from the plates, wash thoroughly with distilled water 3 to 4 times and air dry at room temperature. The crystal violet stained biofilm was solubilised in 95% ethanol (100 μl) and the absorbance measure at 540 nm. Interpret the data from the dose–response curves.

I think it may useful for you...

You can get from the EUCAST homepage detailed information for a standardized broth dilution for fastidious organisms. With this procedure you can determine the MIC and by reculturing the bacteria you can also determine the MBC for your strains.