The effects of essential oils and their major compounds on fish bacterial pathogens – a review

Abstract

The increased resistance of fish pathogens to conventional treatments has lead researchers to investigate the antibacterial properties of natural resources, such as essential oils (EOs) of plants, in an effort to find products that are less harmful to the environment. The objective of this review is to provide an overview of the studies, in vivo and in vitro, that addressed the use of EOs and their major compounds as antimicrobial agents in fish, to identify the best EOs and compounds to investigate considering feasibility of application and suggest possible future studies. To date, studies suggest that the use of EOs in the prevention and/or treatment of infectious diseases in fish may be a promising strategy to reduce the use of conventional antibiotics in aquaculture, since several EOs effectively reduce or avoid the effects of bacterial infections in fish. The use of EOs through nanotechnology delivery systems, especially in dietary supplementation experiments, is promising. This form of application of the EOs allows a potentiation and targeting of the desired effect of the EOs and also allows the protection of EOs active constituents against enzymatic hydrolysis, deserving further study.

In vitro antibacterial activity of four nano-encapsulated herbal essential oils against three bacterial fish pathogens

“…The emergence of antibiotic resistant bacteria due to overuse, the innate antibiotic resistance of Aeromonas species, plus limiting factors of synthetic chemicals due to their potential carcinogenic effects, acute toxicity and environmental hazards has encouraged research into promising substitutes in order to control multidrug resistant microorganisms (Mulyaningsih, Sporer, Zimmermann, Reichling, & Wink, ). Botanical derivatives, in particular plant essential oils (EOs), have shown promise as alternative therapeutic agents (da Cunha, Heinzmann, & Baldisserotto, ; Shin, Prabhakaran, & Kim, ).…”

Effects of dietary Bergamot ( Citrus bergamia ) peel oil on growth, haematology and immune response of European sea bass ( Dicentrarchus labrax ) juveniles

“…Especially, essential oils (EOs) extracted from plants among phytoadditives have a remarkable potential for using in fish diet (Ngugi, Oyoo-Okoth, & Muchiri, 2017;de Souza et al, 2019;Toni et al, 2015). Essential oils contain functional molecules with wide spectrum of biological activity (da Cunha, Heinzmann, & Baldisserotto, 2018). Previous studies showed that EOs added to diets can activate the fish defense system against pathogens, enhance immune function, change microbiota, increase nutrient absorption and nutrient digestibility (Acar, Kesbiç, Yılmaz, Gültepe, & Türker, 2015;Sutili et al, 2016).…”

Dietary organic acids blend alone or in combination with an essential oil on the survival, growth, gut/liver structure and de hemato‐immunological in Nile tilapia Oreochromis niloticus

“…Da Cunha, Heinzmann, and Baldisserotto () suggested that the association of organic acids with essential oils leads to injuries to the cell membrane of pathogenic microorganisms, which increases energy expenditure and limits bacterial growth and multiplication. Langhout () pointed out that this association presents complementary actions on bacterial cells, since the acids act mainly in the diet and in the intestinal tract, whereas essential oils work in the posterior portion of the intestine.…”

“…This would be the probable effect of altering the intestine, where organic acids would be more efficient against Gram‐negative bacteria. This favors probiotic bacteria that are tolerant to low pH and are able to resist and produce organic acids, resulting in beneficial effects on animal health (Basmacioğlu‐Malayoğlu, Ozdemir, & Bağriyanik, ; da Cunha et al, ; He et al, ).…”