title: Change in hydrophilicity of penicillins during advanced oxidation by radiolytically generated OH compromises the elimination of selective pressure on bacterial strains.
abstract: Advanced oxidation processes are promising technologies for removal of antibiotic residues from wastewater in terms of their high efficacy. However, recent studies have reported the remaining antibacterial activity of the products at early-stages of treatment. The present study investigates the effect of such products of model β-lactams (amoxicillin, ampicillin, cloxacillin) on bacteria introducing structure-based, and biological approaches involving Gram-positive and Gram-negative bacterial strains. Chemical analysis revealed the destruction of the β-lactam pharmacophore in competition with the reaction at the aromatic ring. Multisite attack occurs on the penicillin skeleton producing OH-substituted products. The enhanced hydrophilicity confers higher diffusion rate through the porin channels of Gram-negative bacteria and through the hydrophilic cell wall of Gram-positive species. Accordingly, an increase in acute toxicity of treated samples was observed at the beginning of the treatment. The same tendency was observed for target-specific antimicrobial activity investigated with antibiotic susceptibility testing (agar-diffusion, bacterial growth). Prolonged treatments yielded products, e.g. polyhydroxylated phenolic compounds, being also deleterious for bacteria. Therefore, the advanced oxidation process should be judiciously optimized.
authors.affiliation: Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, Konkoly-Thege Miklós út 29-33, H-1121 Budapest, Hungary; Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Szent Gellért tér 4, H-1111 Budapest, Hungary. Electronic address: szabo.laszlo@energia.mta.hu.
authors.forename: László
authors.initials: L
authors.lastname: Szabó
authors.affiliation: Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Szent Gellért tér 4, H-1111 Budapest, Hungary.
authors.forename: Tünde
authors.initials: T
authors.lastname: Tóth
authors.affiliation: Department of Microbiology and Biotechnology, Corvinus University of Budapest, H-1118 Budapest, Hungary.
authors.forename: Tekla
authors.initials: T
authors.lastname: Engelhardt
authors.affiliation: Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, Konkoly-Thege Miklós út 29-33, H-1121 Budapest, Hungary.
authors.forename: Gergely
authors.initials: G
authors.lastname: Rácz
authors.affiliation: Department of Microbiology and Biotechnology, Corvinus University of Budapest, H-1118 Budapest, Hungary.
authors.forename: Csilla
authors.initials: C
authors.lastname: Mohácsi-Farkas
authors.affiliation: Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, Konkoly-Thege Miklós út 29-33, H-1121 Budapest, Hungary; Department of Microbiology and Biotechnology, Corvinus University of Budapest, H-1118 Budapest, Hungary.
authors.forename: Erzsébet
authors.initials: E
authors.lastname: Takács
authors.affiliation: Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, Konkoly-Thege Miklós út 29-33, H-1121 Budapest, Hungary.
authors.forename: László
authors.initials: L
authors.lastname: Wojnárovits
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000633:toxicity; D006090:Gram-Negative Bacteria / Q000187:drug effects; D057927:Hydrophobic and Hydrophilic Interactions; D017665:Hydroxyl Radical / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D010084:Oxidation-Reduction; D010406:Penicillins / Q000737:chemistry* / Q000633:toxicity
chemical_list: D000900:Anti-Bacterial Agents; D010406:Penicillins; D017665:Hydroxyl Radical
keywords: Advanced oxidation; Antibiotic resistance; Bacterial susceptibility; Bacterial toxicity; Hydroxyl radical; Penicillin