Electron microscopic study of the polymyxin treated Vibrio cholerae cells

Polymyxin B produces dose dependent changes in the surface topography of pathogenic Vibrio cholerae cells. The susceptibilities of various vibrio strains to PB are also studied through analytical techniques. Statistical analysis shows significant differences among the four vibrios with regard to their sensitivities to PB, the classical strains being the most sensitive. Treating the classical strain with subinhibitory concentration of PB, we observed with both SEM and TEM that the normal smooth surface of the cell envelope develops some protruded structures (blebs and crenations). Further the TEM study of the ultrathin sections reveal that the rod like projections are formed by protrusions of the outer-membrane of the cell wall.