Development of resistance to chlorhexidine diacetate in Pseudomonas aeruginosa and the effect of a 'residual' concentration

Stable resistance in Pseudomonas aeruginosa NCIMB 10421 was obtained by ste p-wise exposure to gradually increasing concentrations of chlorhexidine dia cetate (CHX). Repeated exposure to a proposed 'residual' (sub-MIC) concentr ation of CHX also created stable resistance. Resistance was also developed bq a single exposure to the 'residual' concentration of CHX, but this was u nstable. Similar experiments with Escherichia coli and CHX or cetylpyridini um chloride resulted in no significant increase in resistance. Antibiotic s usceptibility profiles of the CHX-resistant P. aeruginosa cultures showed n o cross-resistance, although some of the cultures were resistant to benzalk onium chloride. (CV) 2000 The Hospital Infection Society.