Modulation of the antibiotic susceptibility profiles of some microbial strains isolated from wastewater under the influence of the electromagnetic field

Abstract

The wastewater treatment plants are considered to be hotspots for antibiotic resistance selection, transfer and dissemination. Wastewater offers favorable conditions for the development of antibiotic resistant bacteria because it contains high amounts of organic matter, favoring the rapid multiplication of microbial cells and the development of biofilms in which microbial cells are in close proximity, the presence of pollutants (pesticides, heavy metals, antibiotics) acting as selective pressure agents for resistance. The aim of this paper is to investigate how the antibiotics susceptibility profiles of some microbial strains isolated from wastewater are influenced by electromagnetic fields. A number of 10 bacterial strains isolated from wastewater (E. coli, Salmonella sp., Enterobacter sp., Enterococcus sp., Citrobacter sp., Klebsiella sp.) were exposed to an electromagnetic field (50Hz electric field at different voltages) for 24 hours, at 37°C. Thereafter, the antibiotic susceptibility testing was performed for both treated and control strains, by disk diffusion method, according to CLSI 2016. The obtained results proved that the electromagnetic field induced in some cases a decrease of the growth inhibition diameters such as penicillins, cephalosporins, aminoglycosides and vancomycin, while in other cases an increase of bacterial strains susceptibility to the tested antibiotics. These preliminary results demonstrate that the electromagnetic filed in addition with other selective factors which are present in the wastewaters could modulate the environmental reservoir of antibiotic resistance and influence the frequency of the selection of resistant bacteria and the magnitude of the potential risk of dissemination into the environment and of contamination of animals and humans.