ANTIBIOTIC MULTI RESISTANCE OF CORAL-ASSOCIATED BACTERIA IN COMAU FJORD, CHILE

Chile is the world's second largest salmon producer after Norway, however, known for its higher application of antibiotics during rearing in the ocean. This raises concern about its impact on native benthic fauna, like the dense cold-water coral (CWC) banks in the fjords like Comau Fjord. We sampled the common CWC Desmophyllum dianthus close and distant from salmon farm activity. 46 bacterial strains were isolated to assess their resistance to antibiotics using the Kirby-Bauer disc diffusion method. A total of 15 antibiotics were tested including the four most commonly applied antibiotics in salmon farm activity (florfenicol, oxytetracycline, tilmicosin, erythromycin) in addition to commonly used antibiotics in human disease treatment and environmental studies in the region. High antibiotic resistance was found across sites and taxa (mean ± se: 7.0 ± 0.35) with a slight but significantly higher resistance in bacteria cultured from corals collected near compared to distant from salmon farms (7.7 ± 0.47 versus 6.3 ± 0.48, respectively, p = 0.02592). The cultured microbiome indicates a shift from a Pseudoalteromonas-dominated to a Shewanella-dominated microbiome in corals near the salmon farm. This aligns with a shift in the community composition of coral-associated bacteria identified by culture-independent 16S rRNA amplicon sequencing and the dominance of certain taxa close to salmon farms. Together this may suggest that salmon farm activity has the potential to affect benthic organisms and contribute to the spread of bacterial antibiotic resistance within this fjord system.

Presentation Preference: Oral

Primary Presenter: Anna Berezkina, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) (anna.berezkina@awi.de)

Authors:

Anna Berezkina, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research  (anna.berezkina@awi.de)

Ute Hentschel, GEOMAR Helmholtz Centre for Ocean Research  (uhentschel@geomar.de)

Tanja Rahn, GEOMAR Helmholtz Centre for Ocean Research  (trahn@geomar.de)

Claudio Richter, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research; University of Bremen  (claudio.richter@awi.de)

Marlene Wall, GEOMAR Helmholtz Centre for Ocean Research  (mwall@geomar.de)