Unrecognized risk of perfluorooctane sulfonate in promoting conjugative transfers of bacterial antibiotic resistance genes

Effect of environmental factors on conjugative transfer of antibiotic resistance genes in aquatic settings

Antimicrobial-resistance genes (ARGs) are spread among bacteria by horizontal gene transfer, however, the effect of environmental factors on the dynamics of the ARG in water environments has not been very well understood. In this systematic review, we employed the regression tree algorithm to identify the environmental factors that facilitate/inhibit the transfer of ARGs via conjugation in planktonic/biofilm-formed bacterial cells based on the results of past relevant research. Escherichia coli strains were the most studied genus for conjugation experiments as donor/recipient in the intra-genera category. Conversely, Pseudomonas spp., Acinetobacter spp., and Salmonella spp. were studied primarily as recipients across inter-genera bacteria. The conjugation efficiency (ce) was found to be highly dependent on the incubation period. Some antibiotics, such as nitrofurantoin (at ≥0.2 µg ml-1) and kanamycin (at ≥9.5 mg l-1) as well as metallic compounds like mercury (II) chloride (HgCl2, ≥3 µmol l-1), and vanadium (III) chloride (VCl3, ≥50 µmol l-1) had enhancing effect on conjugation. The highest ce value (-0.90 log10) was achieved at 15°C-19°C, with linoleic acid concentrations <8 mg l-1, a recognized conjugation inhibitor. Identifying critical environmental factors affecting ARG dissemination in aquatic environments will accelerate strategies to control their proliferation and combat antibiotic resistance.

Co-selection mechanism for bacterial resistance to major chemical pollutants in the environment

Bacterial resistance is an emerging global public health problem, posing a significant threat to animal and human health. Chemical pollutants present in the environment exert selective pressure on bacteria, which acquire resistance through co-resistance, cross-resistance, co-regulation, and biofilm resistance. Resistance genes are horizontally transmitted in the environment through four mechanisms including conjugation transfer, bacterial transformation, bacteriophage transduction, and membrane vesicle transport, and even enter human bodies through the food chain, endangering human health. Although the co-selection effects of bacterial resistance to chemical pollutants has attracted widespread attention, the co-screening mechanism and co-transmission mechanisms remain unclear. Therefore, this article summarises the current research status of the co-selection effects and mechanism of environmental pollutants resistance, emphasising the necessity of studying the co-selection mechanism of bacteria against major chemical pollutants, and lays a solid theoretical foundation for conducting risk assessment of bacterial resistance.