Simple additives to increase the activity of chlorhexidine digluconate against urinary pathogens

The concentration of chlorhexidine digluconate required to kill Gram-negative bacteria which cause urinary tract infection associated with urethral catheterisation also damages the bladder mucosa. Increased bactericidal activity was obtained by the addition of a chelating agent (EDTA) and a buffer (Tris) enabling a low concentration of chlorhexidine (0.01 per cent) to be effective against Escherichia coli NCTC 86, Pseudomonas aeruginosa NCTC 7650 Proteus mirabilis NCTC 8309 and Streptococcus faecalis NCTC 8213. The type of fluid in which the bacteria were suspended affected the time required to achieve 99.9 per cent killing. The 0.01 per cent chlorhexidine solution with added EDTA and Tris did not cause severe erosive damage to the bladder mucosa of rats. The potential of this solution for use as a skin antiseptic prior to catheterisation and as a bladder instillation after catheterisation is discussed.