| Abstract/Summary | A continuos culture of P. aeruginosa was operated (D50.04 h”1, 792 h) with added benzalkonium chloride (BKC). A derivative, demonstrated a .12-fold decrease in sensitivity to the biocide (MIC .350 mg BKC l”1). The variant demonstrated a 256-fold increase in resistance to ciprofloxacin, with a mutation in gyrA. Similarly, culturing of the original strain in continuous culture with ciprofloxacin led to evolution of BKC-adapted populations. Efflux pump activity predominantly contributed to the phenotype. An amino acid substitution in nfxB, the Mex efflux system regulator gene, was observed for PA-29. Overexpression of MexAB-OprM and MexCD-OprJ was recorded. Results indicate the importance of environmental conditions on selection and maintenance of biocide adaptation. Microbiology. 2010 Jan;156(Pt 1):30-8. Epub 2009 Oct 8. |