Electron beam treatment for tackling the escalating problems of antibiotic resistance: Eliminating the antimicrobial activity of wastewater matrices originating from erythromycin

A synthetic effluent wastewater matrix was designed to be a kinetically appropriate reflection of a real sample while containing the antibiotic erythromycin at sufficiently high concentration for the microbiological assay. Following preliminary experiments on S. aureus isolates resistant and susceptible subtypes could be obtained against erythromycin. Agar diffusion and broth microdilution assays indicated antibacterial activity of the products forming in treated dilute aqueous solution of the antibiotic, however, also showed the applicability of EB treatment to eliminate their activity. In the complex wastewater matrix despite the high amount of secondary radicals forming from the matrix components (e.g. humic acid, HCO3-) the elimination of the antibacterial activity is suggested to follow the stoichiometry of center dot OH in respect to the antibiotic in line with dilute aqueous solution. Although there will be cases when secondary radicals will help degrading a molecule, the technology needs to be designed to the stoichiometric presence of center dot OH according to the worst-case scenario approach. (C) 2017 Elsevier B.V. All rights reserved.