Abstract
A new emerging phenomenon is the association between the incorrect use of biocides in the process of disinfection in farms and the emergence of cross-resistance in Salmonella populations. Adaptation of the microorganisms to the sub-inhibitory concentrations of the disinfectants is not clear, but may result in an increase of sensitivity or resistance to antibiotics, depending on the biocide used and the challenged Salmonella serovar. Exposure of five Salmonella enterica subsp. enterica serovar Senftenberg (S. Senftenberg) strains to triamine-containing disinfectant did not result in variants with resistance to antibiotics, but has changed their susceptibility to normal human serum (NHS). Three biocide variants developed reduced sensitivity to NHS in comparison to the sensitive parental strains, while two isolates lost their resistance to serum. For S. Senftenberg, which exhibited the highest triamine tolerance (6 × MIC) and intrinsic sensitivity to 22.5% and 45% NHS, a downregulation of flagellin and enolase has been demonstrated, which might suggest a lower adhesion and virulence of the bacteria. This is the first report demonstrating the influence of biocide tolerance on NHS resistance. In conclusion, there was a potential in S. Senftenberg to adjust to the conditions, where the biocide containing triamine was present. However, the adaptation did not result in the increase of antibiotic resistance, but manifested in changes within outer membrane proteins’ patterns. The strategy of bacterial membrane proteins’ analysis provides an opportunity to adjust the ways of infection treatments, especially when it is connected to the life-threating bacteremia caused by Salmonella species.
Highlights
Cross-resistance to antibiotics of bacteria exposed to disinfectants is an increasing problem for public health as cross-resistant phenotypes of microorganisms could potentially develop into life-threatening infections
We demonstrated that growth of Salmonella enterica subsp. enterica serovars Enteritidis, Typhimurium, Virchow and Zanzibar isolated from human fecal samples with sub-inhibitory concentrations of farm disinfectants containing dodecylamine led to increased isolation of multiple antibiotic-resistant strains [8,9]
We found that the threshold for the bacterial growth was the concentration of the biocide of 8 × MIC (Minimal Inhibitory Concentration) in the LB medium, which was lethal for all tested microorganisms
Summary
Cross-resistance to antibiotics of bacteria exposed to disinfectants (biocides) is an increasing problem for public health as cross-resistant phenotypes of microorganisms could potentially develop into life-threatening infections. A single exposure to some biocides has been found to be insufficient to select for multidrug-resistant (MDR) strains; repeated, sub-inhibitory exposure to biocides does result in the selection of MDR bacteria [3]. Enterica serovars Enteritidis, Typhimurium, Virchow and Zanzibar isolated from human fecal samples with sub-inhibitory concentrations of farm disinfectants containing dodecylamine (triamine) led to increased isolation of multiple antibiotic-resistant strains [8,9]. The antimicrobial efficacy of commercially-manufactured disinfectant substances (represented by quaternary ammonium salts (QAC) and QAC combined with other additives) were tested against Salmonella Enteritidis strains by others [7,10]
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