Understanding benzalkonium chloride tolerance and its implications in antibiotic resistance and other phenotypes in clinical isolates of Klebsiella pneumoniae

Abstract

In this study, clinical isolates of Klebsiella pneumoniae, a Gram-negative pathogen associated with hospital acquired infections, were tested for both phenotypic and genotypic changes following adaptation to the commonly used disinfecting agent benzalkonium chloride. Changes in antibiotic susceptibility and susceptibility to other disinfectants were assessed using broth microdilution, and changes in colony morphology and capsule density were also determined. Assays using ethidium bromide and Hoechst H33342 fluorescent dye were also performed to observe changes in efflux activity and accumulation following adaptation to benzalkonium chloride.

It was found that bacterial cells which had been repeatedly exposed to sub-inhibitory concentrations of benzalkonium chloride showed greater tolerance to the biocide, but this did not correspond to a change in antibiotic resistance profile or confer cross-resistance with other biocides. Capsule density and efflux/accumulation were found to be the most impacted phenotypes in the adapted strains, with strains showing decreased capsule densities and increased efflux following adaptation.