You can multiply the pathogenic bacteria in LB broth media. Then you have to take spectophotometer reading (OD) at 600 nm wavelength. You have to adjust the cell count to the optimum for that genus you have ( eg. for Ralstonia, 10^6 to 10^7 cells per ml). You have to take up sowing in autoclaved soil or any other media and then the suspension can be drenched in that media.