Efflux pump activity in fluoroquinolone and tetracycline resistant Salmonella and E. coli implicated in reduced susceptibility to household antimicrobial cleaning agents.

Whereas it has been shown that the inappropriate use of antimicrobial household agents selects for organisms with resistance mechanisms, which could lead to the development of antibiotic resistance, the hypothesis, that antibiotic-resistant organisms become tolerant to disinfectants due to the action of efflux pumps, has not been examined. In this study, tetracycline and ofloxacin sensitive and resistant Escherichia coli (9 strains) and Salmonella spp. (8 strains) were isolated from poultry and clinical samples. In order to assess whether these bacteria had active efflux pumps, ethidium bromide accumulation assays were performed. Extrusion of the active components of three commercial household agents (triclosan, sodium salicylate, and ortho-phenylphenol) by efflux pumps was tested using spectrophotometric accumulation assays. In order to simulate the kitchen environment, in-use disinfectant testing using the commercial household agents was performed. Active efflux pump activity and extrusion of all three active ingredients was observed only in the antibiotic resistant organisms. The antibiotic sensitive bacteria were also more susceptible than the resistant isolates to the household antimicrobial agents at below recommended concentrations. Int J Food Microbiol. 2007 Feb 15;113(3):315-20. Epub 2006 Nov 27.