title: Antibacterial activity of oxytetracycline photoproducts in marine aquaculture's water.
abstract: Oxytetracycline (OTC) is one of the most used antibiotics in aquaculture. The main concern related to its use is the bacterial resistance, when ineffective treatments are applied for its removal or inactivation. OTC photo-degradation has been suggested as an efficient complementary process to conventional methods used in intensive fish production (e.g.: ozonation). Despite this, and knowing that the complete mineralization of OTC is difficult, few studies have examined the antibacterial activity of OTC photoproducts. Thus, the main aim of this work is to assess whether the OTC photoproducts retain the antibacterial activity of its parent compound (OTC) after its irradiation, using simulated sunlight. For that, three Gram-negative bacteria (Escherichia coli, Vibrio sp. and Aeromonas sp.) and different synthetic and natural aqueous matrices (phosphate buffered solutions at different salinities, 0 and 21‰, and three different samples from marine aquaculture industries) were tested. The microbiological assays were made using the well-diffusion method before and after OTC has been exposed to sunlight. The results revealed a clear effect of simulated sunlight, resulting on the decrease or elimination of the antibacterial activity for all strains and in all aqueous matrices due to OTC photo-degradation. For E. coli, it was also observed that the antibacterial activity of OTC is lower in the presence of sea-salts, as demonstrated by comparison of halos in aqueous matrices containing or not sea-salts.
authors: Department of Chemistry, University of Aveiro, Portugal; CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Portugal. Electronic address: joanaleal@ua.pt.
authors: J F
authors: JF
authors: Leal
authors: Department of Biology, University of Aveiro, Portugal; CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Portugal; Institute for Research in Biomedicine-iBiMED, Health Sciences Program, University of Aveiro, Portugal. Electronic address: ihenriques@ua.pt.
authors: I S
authors: IS
authors: Henriques
authors: Department of Biology, University of Aveiro, Portugal; CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Portugal.
authors: A
authors: A
authors: Correia
authors: Department of Chemistry, University of Aveiro, Portugal; CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Portugal. Electronic address: edsantos@ua.pt.
authors: E B H
authors: EBH
authors: Santos
authors: Department of Chemistry, University of Aveiro, Portugal; CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Portugal. Electronic address: valdemar@ua.pt.
authors: V I
authors: VI
authors: Esteves
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis / Q000737:chemistry* / Q000494:pharmacology* / Q000528:radiation effects; D017756:Aquaculture / Q000379:methods; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D010118:Oxytetracycline / Q000032:analysis / Q000737:chemistry* / Q000494:pharmacology* / Q000528:radiation effects; D010782:Photolysis / Q000528:radiation effects*; D011174:Portugal; D054712:Salinity; D013472:Sunlight; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology / Q000528:radiation effects
chemical_list: D000900:Anti-Bacterial Agents; D014874:Water Pollutants, Chemical; D014867:Water; D010118:Oxytetracycline
keywords: Antibiotics; Biological activity; Kinetics; Marine aquaculture; Photolysis