Genetic capitalism and stabilizing selection of antimicrobial resistance genotypes in Escherichia coli

Long-term exposure to food-grade disinfectants causes cross-resistance to antibiotics in Salmonella enterica serovar Typhimurium strains with different antibiograms and sequence types

BACKGROUND

Disinfectants are important in the food industry to prevent the transmission of pathogens. Excessive use of disinfectants may increase the probability of bacteria experiencing long-term exposure and consequently resistance and cross-resistance to antibiotics. This study aims to investigate the cross-resistance of multidrug-resistant, drug-resistant, and drug-susceptible isolates of Salmonella enterica serovar Typhimurium (S. Typhimurium) with different sequence types (STs) to a group of antibiotics after exposure to different food-grade disinfectants.

METHODS

A panel of 27 S. Typhimurium strains with different antibiograms and STs were exposed to increasing concentrations of five food-grade disinfectants, including hydrogen peroxide (H2O2), benzalkonium chloride (BAC), chlorine dioxide (ClO2), sodium hypochlorite (NaClO), and ethanol. Recovered evolved strains were analyzed using genomic tools and phenotypic tests. Genetic mutations were screened using breseq pipeline and changes in resistance to antibiotics and to the same disinfectant were determined. The relative fitness of evolved strains was also determined.

RESULTS

Following exposure to disinfectants, 22 out of 135 evolved strains increased their resistance to antibiotics from a group of 14 clinically important antibiotics. The results also showed that 9 out of 135 evolved strains had decreased resistance to some antibiotics. Genetic mutations were found in evolved strains. A total of 77.78% of ST34, 58.33% of ST19, and 66.67% of the other STs strains exhibited changes in antibiotic resistance. BAC was the disinfectant that induced the highest number of strains to cross-resistance to antibiotics. Besides, H2O2 induced the highest number of strains with decreased resistance to antibiotics.

CONCLUSIONS

These findings provide a basis for understanding the effect of disinfectants on the antibiotic resistance of S. Typhimurium. This work highlights the link between long-term exposure to disinfectants and the evolution of resistance to antibiotics and provides evidence to promote the regulated use of disinfectants.

High plasmidome diversity of extended-spectrum beta-lactam-resistant Escherichia coli isolates collected during one year in one community hospital

Plasmid-encoded antibiotic resistance encompasses many classes of currently used antibiotics. In globally distributed Escherichia coli lineages plasmids, which spread via horizontal gene transfer, are responsible for the dissemination of genes encoding extended-spectrum β-lactamases (ESBL). In this study, we combined 2nd and 3rd generation sequencing techniques to reconstruct the plasmidome of overall 97 clinical ESBL-E. coli isolates. Our results highlight the enormous plasmid diversity in respect to size, replicon-type and genetic content. Furthermore, we emphasize the diverse plasmid distribution patterns among the clinical isolates and the high intra- and extracellular mobility potential of resistance conferring genes. While the majority of resistance conferring genes were located on large plasmids of known replicon type, small cryptic plasmids seem to be underestimated resistance gene vectors. Our results contribute to a better understanding of the dissemination of resistance-conferring genes through horizontal gene transfer as well as clonal spread.