Development of resistance to chlorhexidine diacetate and cetylpyridinium chloride in Pseudomonas stutzeri and changes in antibiotic susceptibility

Strains of Pseudomonas stutzeri developed stable resistance to chlorhexidine diacetate (CHA) or cetylpyridinium chloride (CPC) when exposed to gradually increasing concentrations of either antibacterial agent. Such strains showed reduced sensitivity to other non-antibiotics, including triclosan, and to some antibiotics, although this varied from strain to strain. Resistant strains were inactivated less readily by CHA or CPC and were less sensitive to sodium dodecyl sulphate. Some CHA-resistant and some CPC-resistant strains were more hydrophobic than the parent strains. Alterations in the cell envelope are likely to be responsible for non-specific changes in sensitivity to several antibacterial agents. Attempts to transfer CHA or CPC resistance by conjugation were unsuccessful. DNA from some CHA- or CPC-resistant strains could transform Ps. stutzeri strain JM 302, a histidine auxotroph, to prototrophy.