Abstract
Bacterial pathogens are a major cause of infectious diseases in aquatic animals. The abuse of antibiotics in the aquatic industry has led to the proliferation of antibiotic resistance. It is therefore essential to develop more effective and safer strategies to increase the efficacy and extend the life span of the antibiotics used in aquaculture. In this study, we show that six aquaculture bacterial pathogens (i.e., Aeromonas hydrophila, Vibrio alginolyticus, Edwardsiella tarda, Streptococcus iniae, Vibrio harveyi, and Vibrio fluvialis) in the stationary phase can be rapidly killed after immersion in gentamicin- or neomycin-containing, ion-free solutions for a few minutes. Such hypoionic shock treatment enhances the bacterial uptake of gentamicin in an ATP-dependent manner. Importantly, we demonstrate, as a proof of concept, that gentamicin under hypoionic shock conditions can effectively kill A. hydrophila in vivo in a skin infection model of zebrafish (Danio rerio), completely curing the infected fish. Given that pathogenic bacteria generally adhere to the skin surface and gills of aquatic animals, our strategy is of potential significance for bacterial infection control, especially for small-scale economic fish farming and ornamental fish farming. Further, the combined treatment can be completed within 5 min with a relatively small volume of solution, thus minimizing the amount of residual antibiotics in both animals and the environment.
Highlights
Aquaculture is the fastest-growing animal food industry at present and provides human society with one of the most sustainable forms of edible protein and nutrient production, making it a fundamental part of future food production (Froehlich et al, 2018)
We show that six aquaculture bacterial pathogens (i.e., Aeromonas hydrophila, Vibrio alginolyticus, Edwardsiella tarda, Streptococcus iniae, Vibrio harveyi, and Vibrio fluvialis) in the stationary phase are killed rapidly in vitro by gentamicin and neomycin under hypoionic shock conditions
We examined the antibiotic tolerance of six aquaculture bacteria, Aeromonas hydrophila, Vibrio alginolyticus, Vibrio fluvialis, Vibrio harveyi, Edwardsiella tarda, and Streptococcus iniae, by treating the stationary-phase cells with aminoglycoside antibiotics dissolved in 0.9% NaCl solution (Figure 1 and Supplementary Figure S1)
Summary
Aquaculture is the fastest-growing animal food industry at present and provides human society with one of the most sustainable forms of edible protein and nutrient production, making it a fundamental part of future food production (Froehlich et al, 2018). Fish diseases are often caused by bacteria, viruses, fungi, parasites, or a combination of these pathogens, with bacterial pathogens. Given that bacteria can survive well in aquatic environments independent of a host, bacterial diseases have become major impediments to aquaculture (Haenen et al, 2013). Various effective vaccines have been developed against many fish bacterial pathogens. Attenuated bacterial vaccines can potentially revert to a pathogenic form, which poses a tremendous risk to the whole environment (Matsuura et al, 2019). Some bacterial pathogens are difficult to culture or completely unculturable, making them unsuitable for vaccine development (Takano et al, 2016)
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