Freshwater salmon aquaculture in Chile and transferable antimicrobial resistance

Abstract

Large amounts of antimicrobials are used in salmonid aquaculture in Chile. Most are used in marine aquaculture, but appreciable amounts are also employed in freshwater aquaculture. Much research and many publications have examined transferable antimicrobial resistance in bacteria isolated from marine salmon farms, but much less attention has been paid to this area in freshwater salmon farming. A recent paper by Domínguez et al. (2019) has as least in part remedied this situation. We now comment on some of its interpretations and have attempted to point out its areas of strength and weakness in light of the published scientific literature. Seen in this setting, the important results presented by Domínguez et al. (2019) underline the need for increased awareness of the challenge to animal and human health posed by excessive use of antimicrobials in aquaculture.There have been several molecular studies of antimicrobial-resistant bacteria in Chilean salmon aquaculture but most have focused on marine rather than on freshwater salmonid aquaculture. This is not surprising since over 95% of the antimicrobials used in Chilean aquaculture are used in marine salmon aquaculture (Millanao et al.

Farm animals and aquaculture: significant reservoirs of mobile colistin resistance genes

“…The human health could be impacted by antimicrobial-resistant bacteria via intake of contaminated food and water, as well as through contact between animals and humans (Holmes et al, 2016). It is considered that excessive usage of antimicrobial agents in animal production and aquaculture leads to antimicrobial-resistant bacteria surviving in animals and the environment and also in food of animal origin following cross-contamination with antimicrobial-resistant bacteria during animal slaughter and/or food processing (Verraes et al, 2013;Jans et al, 2018;Cabello et al, 2020). Moreover, a contamination of the environment can occur via excretions of grazing animals or using liquid manure as fertilizer, both containing antimicrobial resistant bacteria and genes (Zhu et al, 2013;Cabello et al, 2016;Ruuskanen et al, 2016;Ercumen et al, 2017).…”

Misunderstandings and misinterpretations: Antimicrobial use and resistance in salmon aquaculture

“…Only 1.3% of the over 463 tons of antimicrobials used in salmon aquaculture in Chile in 2021 were used in freshwater aquaculture (Sernapesca, 2022 ). This strongly indicates the major risk regarding the selection of antibiotic‐resistant bacteria and antimicrobial resistance genes lies in the saltwater aquaculture phase (Avendaño‐Herrera et al, 2022 ; Cabello et al, 2020 ; Salgado‐Caxito et al, 2022 ). Moreover, antimicrobials used in the oceanic phase of salmon aquaculture are more likely to select for antimicrobial resistances closer to the consumer, since salmon fillets are prepared from salmon grown in saltwater and not in freshwater.…”

Biological Effects of Quinolones: A Family of Broad-Spectrum Antimicrobial Agents

“…However, the studies carried out by Tomova et al, also found that strains of marine bacteria, from areas impacted by using antimicrobials in aquaculture, and strains of uropathogenic E. coli share identical qnr genes. In addition to the qnr genes, structural similarity in class 1 integrons, identical gene cassettes and sequence similarity in their flanking regions were found, suggesting that use of antimicrobials in aquaculture could facilitate HGT among these bacterial populations of different environmental compartments [ 326 , 327 ]. Figure 6 illustrates the mechanisms by which DNA might be acquired horizontally.…”