Cleaning and disinfection is an integral component of livestock production. There is some evidence, based on laboratory experiments, that suggests that exposure of bacteria to sub-inhibitory concentrations of disinfectants may facilitate selection for disinfectant and antimicrobial resistance. Laboratory-based experiments have shown that step-wise exposure of initially susceptible bacteria to sub-inhibitory concentrations of benzalkoniumchloride, chlorhexidine, triclosan and some commercial disinfectants may lead to decreased susceptibility to either antibiotics or disinfectants.The recommended concentrations of farm disinfectants is normally well above the minimum inhibitory concentration (MIC) of disease causing agents. Because commercial disinfectants often contain more than one type of active disinfectant component having different antimicrobial mode of action the development of resistance at recommended rates should be highly unlikely. In the real world, however, bacteria may be exposed to disinfectants at sub-inhibitory concentrations due to mixing errors, the presence of residual organic debris that is not removed during cleaning or to the dilution effect of remaining rinse water.
Researchers wanted to look for “real world” evidence for the likelihood that sub-inhibitory concentrations could lead to selection of strains of E. coli with increased disinfectant and antimicrobial resistance.The results of this study were as follows:
- As a base level, there was a high resistance prevalence (>50%) for ampicillin, sulfamethoxazole, trimethoprim and tetracycline for both poultry and pigs. Ciprofloxacin resistance prevalence was primarily a broiler house issue.
- Disinfectant susceptibility results were homogenously distributed within a very small concentration range.
- All E. coli strains were susceptible to in-use concentrations of formaldehyde, benzalkoniumchloride and a formulation of peracetic acid and hydrogen peroxide, indicating that the practical use of disinfectants did not select for disinfectant resistance.
- There was no evidence for the selection of antibiotic resistant bacteria through the use of disinfectants in agricultural environments.
Take Home Message
- The use of disinfectants under practical farm conditions does not appear to increase the risk of either disinfectant or antimicrobial resistance in bacteria.
- Although these results are comforting it is important to recognize that this particular study was limited to one geographic region and one type of bacteria (E. coli)
Submitted by Greg Wideman, DVM
Ref: Maertens H, De Reu K, Meyer E, Van Coillie E, Dewulf J.Limited association between disinfectant use and either antibiotic or disinfectant susceptibility of Escherichia coli in both poultry and pig husbandry.BMC Vet Res. 2019 Sep 2;15(1):310. doi: 10.1186/s12917-019-2044-0