Abstract

It has been shown that the inappropriate use of antimicrobial household agents selects for organisms with resistance mechanisms (e.g. efflux pumps), which could lead to the development of antibiotic resistance. The reverse hypothesis, that antibiotic-resistant organisms become tolerant to other antibacterial agents (e.g. disinfectants) due to the action of efflux pumps, has however not been extensively examined. The objective of this study was to establish whether there is a link between antibiotic resistance in potential gastrointestinal pathogens and reduced sensitivity of these organisms to commonly used household antimicrobial agents. 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 to determine changes in their efficacy due to antibiotic resistance. 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 concentrations below that recommended by the manufacturer. These resistant bacteria could potentially be selected for and result in hard to treat infections.

Keywords: Household antimicrobials; Efflux pump; Food pathogens

Article Outline

1. Introduction

2. Materials and methods

2.1. Bacterial strains

2.2. Media

2.3. Isolation of bacteria from poultry and clinical samples

2.4. Identification and susceptibility testing

2.5. Ethidium bromide accumulation assays

2.6. Measurement of chemical accumulation

2.7. In-use disinfection procedure

2.8. Statistical analysis

3. Results

3.1. Bacterial strains

3.2. Ethidium bromide accumulation

3.3. Measurement of chemical accumulation

3.4. In-use disinfection procedure

4. Discussion

Acknowledgements

References