Abstract

The need to discover new natural compounds has become urgent as a possible alternative solution to contrast the spread of antibiotic resistance, also in the aquaculture field. Bacterium–bacterium inhibitory activity against bacterial pathogens relevant in aquaculture was evaluated on agar plates for bacteria isolated from cold Arctic (Kongsfjorden, Svalbard Islands; i.e., seawater and sediment samples) and temperate Mediterranean (Lake Faro in Messina and the Straits of Messina, Italy; i.e., brackish water and benthic filter-feeding organisms) environments. Cell-free supernatants (both pure and concentrated 10-fold) were further assayed and, in the case of a positive response, crude extracts were obtained and tested. After the pre-screening procedures, about 30% of the bacterial isolates inhibited the growth of at least one pathogen used as a target. The 10-fold concentrated supernatants of two Arctic Salinibacterium spp. strains and the Mediterranean Bacillus sp. PS62 (associated with the pennatulacean Pteroeides spinosum Ellis, 1764) resulted in being active against P. damselae subsp. piscicida. The crude extracts obtained from Bacillus sp. PS62 also showed inhibitory activity against the same pathogen. Our findings suggest that tested bacteria could represent a novel source of compounds to be applied to overcome pathogenesis in the aquaculture field.

Highlights

  • In the last few decades, as a consequence of the strong over-fishing actions and the subsequent pauperization of ichthyic resources, the aquaculture field has gained interest in supporting and providing complementary activity to fisheries, in order to increase profits both qualitatively and quantitatively.farming activities of aquatic species are not exempt of problems, such as the exploitation of environmental and biological resources, the spillage of effluents rich in residual nutrients, and the emergence of fish diseases by bacterial etiological agents with huge economic losses [1,2,3,4]

  • Our findings suggest that tested bacteria could represent a novel source of compounds to be applied to overcome pathogenesis in the aquaculture field

  • In this study we proposed a step-by-step screening procedure to detect bioactivity in bacterial strains of different origins (Arctic water and sediment, and Mediterranean benthic organisms and brackish waters) against bacterial pathogens with relevance in aquaculture

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Summary

Introduction

Farming activities of aquatic species are not exempt of problems, such as the exploitation of environmental and biological resources, the spillage of effluents rich in residual nutrients, and the emergence of fish diseases by bacterial etiological agents with huge economic losses [1,2,3,4]. In this latter regard, different bacterial strains are known to be responsible for diseases in farmed fish, mollusks and crustaceans. The bacterial production of bioactive molecules (including both broad-spectrum and species-specific activities) [16,17] against pathogens with relevance in aquaculture remains scantly investigated

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