Electron microscope study of the effect of benzalkonium, chlorhexidine and polymyxin on Pseudomonas cepacia

Electron micrographs of Pseudomonas cepacia cell grown in nutrient broth show an external membrane which is distinctly wavy, when compared with similar preparations of Pseudomonas aeruginosa, and which is not affected by growing in the presence of broth containing benzalkonium (10 microgram/ml), chlorhexidine (10 microgram/ml) or polymyxin (25 units/ml). Both benzalkonium (10 microgram/ml) and chlorhexidine (10 microgram/ml) damage the cytoplasmic membrane of P. cepacia cell grown in the presence of the chemicals. Contrasts are shown between the effect of polymyxin (chlorhexidine and benzalkonium) on the outer membrane of P. cepacia and P. aeruginosa.