Cytological changes in chlorhexidine-resistant isolates of Pseudomonas stutzeri

Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive analysis of X-ray (EDAX) have been used to examine ch lorhexidine diacetate (CHA)-sensitive and -resistant isolates of Pseudomona s stutzeri and to determine the effects of CHA on the cells, Significant di fferences were observed in the structure, size and elemental composition of CHA-sensitive and -resistant cells, Treatment with CHA produced considerab ly greater changes in CHA-sensitive cells, with widespread peeling of the o uter membrane, a substantial loss of cytoplasmic electron-dense material an d extensive lysis, Cells from the resistant isolates showed no blebbing of the outer membrane and no structural damage. X-ray mapping confirmed the di fference in CHA uptake between CHA-sensitive and CHA-resistant cells, It is proposed that changes in the outer membrane form a major mechanism of resi stance to CHA in P. stutzeri.