Differentiative evaluation of antibiotics for their ability to limit the sliding motility of Mycobacterium smegmatis

To evaluate some molecular species exhibiting antibacterial activity for their ability to limit the sliding motility of mycobacteria we developed differential method, including the measuring of sliding colony square (mm2) in combination with enumeration of cell number per 1 mm2 of the square. These parameters were used to differentiate inhibition of sliding motility from killing effect of antibacterials and were measured over a range of concentrations. The limiting effect on sliding motility was registered when the square of sliding colony decreased while the cell number per 1 mm2 of its square proportionally increased at subinhibitory concentrations. This effect was observed for rifampicin, however, tetracycline and streptomycin restricted the sliding colony size through their killing effects on Mycobacterium smegmatis cells.