Antibacterial Effects of Essential Oils of Seven Medicinal-Aromatic Plants Against the Fish Pathogen Aeromonas veronii bv. sobria: To Blend or Not to Blend?

Manolis Mandalakis,Pantelis Katharios,Vasileios Greveniotis,Nikos Krigas,Efthimia Antonopoulou,Sofoklis Keisaris,Thekla I Anastasiou,Natalia Martou,Diamanto Lazari

doi:10.3390/molecules26092731

Manolis Mandalakis, Pantelis Katharios + Show 7 more

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https://doi.org/10.3390/molecules26092731

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Abstract

Despite progress achieved, there is limited available information about the antibacterial activity of constituents of essential oils (EOs) from different medicinal-aromatic plants (MAPs) against fish pathogens and the complex interactions of blended EOs thereof. The present study aimed to investigate possible synergistic antimicrobial effects of EOs from seven Greek MAPs with strong potential against Aeromonas veronii bv. sobria, a fish pathogen associated with aquaculture disease outbreaks. The main objective was to evaluate whether blending of these EOs can lead to increased antimicrobial activity against the specific microorganism. A total of 127 combinations of EOs were prepared and their effect on A. veronii bv. sobria growth was tested in vitro. We examined both the inhibitory and bactericidal activities of the individual EOs and compared them to those of the blended EOs. The vast majority of the investigated combinations exhibited significant synergistic and additive effects, while antagonistic effects were evident only in a few cases, such as the mixtures containing EOs from rosemary, lemon balm and pennyroyal. The combination of EOs from Greek oregano and wild carrot, as well as the combinations of those two with Spanish oregano or savoury were the most promising ones. Overall, Greek oregano, savoury and Spanish oregano EOs were the most effective ones when applied either in pure form or blended with other EOs.

Highlights

IntroductionThe bacterium Aeromonas veronii Hickman-Brenner et al 1988 poses a serious threat worldwide to the aquaculture industry as it is responsible for mortality outbreaks in a variety of farmed fish, including Nile tilapia (Oreochromis niloticus Linnaeus 1758) [1], African catfish (Clarias gariepinus Burchell 1822), rajputi (Puntius gonionotus Bleeker 1850), rui (Labeo rohita Hamilton 1822), catla (Catla catla Hamilton 1822), and shole (Channa striatus Bloch 1793) [2], Chinese longsnout catfish (Leiocassis longirostris Günther 1864) [3], loach (Misgurnus anguillicaudatus Cantor 1842) [4] and European seabass (Dicentrachus labrax Linnaeus 1758) [5]
The present study aimed to investigate possible synergistic antimicrobial effects of essential oils (EOs) from seven Greek medicinal-aromatic plants (MAPs) with strong potential against Aeromonas veronii bv. sobria, a fish pathogen associated with aquaculture disease outbreaks
The bacterium Aeromonas veronii Hickman-Brenner et al 1988 poses a serious threat worldwide to the aquaculture industry as it is responsible for mortality outbreaks in a variety of farmed fish, including Nile tilapia (Oreochromis niloticus Linnaeus 1758) [1], African catfish (Clarias gariepinus Burchell 1822), rajputi (Puntius gonionotus Bleeker 1850), rui (Labeo rohita Hamilton 1822), catla (Catla catla Hamilton 1822), and shole (Channa striatus Bloch 1793) [2], Chinese longsnout catfish (Leiocassis longirostris Günther 1864) [3], loach (Misgurnus anguillicaudatus Cantor 1842) [4] and European seabass (Dicentrachus labrax Linnaeus 1758) [5]

Summary

Introduction

The bacterium Aeromonas veronii Hickman-Brenner et al 1988 poses a serious threat worldwide to the aquaculture industry as it is responsible for mortality outbreaks in a variety of farmed fish, including Nile tilapia (Oreochromis niloticus Linnaeus 1758) [1], African catfish (Clarias gariepinus Burchell 1822), rajputi (Puntius gonionotus Bleeker 1850), rui (Labeo rohita Hamilton 1822), catla (Catla catla Hamilton 1822), and shole (Channa striatus Bloch 1793) [2], Chinese longsnout catfish (Leiocassis longirostris Günther 1864) [3], loach (Misgurnus anguillicaudatus Cantor 1842) [4] and European seabass (Dicentrachus labrax Linnaeus 1758) [5]. Antibiotics, probiotics, prebiotics, algae, phages, minerals, nanoparticles, plants and essential oils have all been recruited to deal with severe infections caused by Aeromonas spp. The increasing resistance of fish pathogens to conventional antibiotics and the societal demand for less harmful fish products and concomitant processes from environmental/sustainability viewpoint has channeled research towards alternative treatments of bacterial infections. There is growing interest about the antibacterial properties of natural resources and natural products, such as essential oils (EOs) of medicinal-aromatic plants (MAPs) [9]

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