Antibiotics at environmentally relevant concentrations can promote the dissemination of antibiotic resistance via both vertical and horizontal gene transfer
Yue Wang, Yifan Liu, Jie Yang, Mengke Geng, Hui Jia, Jie Wang
Abstract
Antibiotic resistance has emerged as a significant global threat to human health and is considered a biocontaminant. Both vertical gene transfer (VGT) and horizontal gene transfer (HGT) play important roles in the spread of antibiotic resistance. The impact of environmentally relevant concentrations of typical antibiotics on the spread of antibiotic resistance genes (ARGs) through these two modes of transmission, as well as the underlying mechanisms, remains an urgent area of research. This study explores the effects of four typical antibiotics (tetracycline, ampicillin, kanamycin, and streptomycin) at environmental concentrations on the genetic stability and horizontal transfer of ARGs across three models (vertical transfer, conjugation, and transformation), along with the mechanisms involved. We conclude that, except for tetracycline, antibiotics exposed to the other three environmental concentrations could potentiate the persistence of resistance in resistant bacteria. Furthermore, all antibiotics, at concentrations ranging from 0.005 to 5 mg/L, were able to induce horizontal shifts in ARGs. Various metrics were employed in the phenotypic and genotypic analyses. The results indicated that enhanced resistance following exposure to antibiotics was directly correlated with the overproduction of reactive oxygen species, an elevated stress response, strengthened efflux pump activity, and intensified cell membrane permeability. Mathematical models were also used to predict the impact of prolonged bacterial exposure to antibiotics on the stability of ARGs and plasmid transformation. Our findings highlight the risks associated with the development of antibiotic resistance under environmentally relevant concentrations of antibiotics.