Evaluation of the in vitro antibacterial activity of some essential oils and their blends against Staphylococcus spp. isolated from episodes of sheep mastitis

Filippo Fratini,Margherita Giusti,Simone Mancini,Basma Najar,Francesca Pisseri,Luisa Pistelli

doi:10.1007/s12210-021-00991-5

Filippo Fratini, Margherita Giusti + Show 4 more

Open Access

https://doi.org/10.1007/s12210-021-00991-5

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Abstract

Staphylococcus aureus and coagulase-negative staphylococci are among the major causes of mastitis in sheep. The main goal of this research was to determine the in vitro antibacterial activity of several essential oils (EOs, n 30), then five of them were chosen and tested alone and in blends against staphylococci isolates. Five bacteria were isolated from episodes of ovine mastitis (two S. aureus and three S. xylosus). Biochemical and molecular methods were employed to identify the isolates and disk diffusion method was performed to determine their antimicrobial-resistance profile. The relative percentage of the main constituents in the tested essential oils and their blends was detected by GC-EIMS analysis. Antibacterial and bactericidal effectiveness of essential oils and blends were evaluated through minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). All of them showed sensitivity to the used antimicrobials. The EOs with the highest antibacterial activity were those belonging to the Lamiaceae family characterized by high concentrations of thymol, carvacrol and its precursor p-cymene, together with cinnamon EO, rich in cinnamaldehyde. In terms of both MIC and MBC values, the blend composed by Thymus capitatus EO 40%, Cinnamomum zeylanicum EO 20%, Thymus serpyllum EO 20% and Satureja montana EO 20% was found to be the most effective against all the isolates. Some essential oils appear to represent, at least in vitro, a valid tool against ovine mastitis pathogens. Some blends showed a remarkable effectiveness than the single oils, highlighting a synergistic effect in relation to the phytocomplex.

Highlights

Mastitis is one of the most important health problem in dairy sheep worldwide
The phytocomplex contained in a single essential oils (EOs), which consists of compounds of several different functional-group classes, can be used alone or in association with other phytocomplexes providing a multiplicity of pharmacological actions, related to the presence of active compounds that may perform various functions and others that modulate the effect (Pisseri et al 2008; Marassi and Rossi 2015)
Thymus serpyllum and Satureja montana belong to the Lamiaceae family, which includes plants with a wide range of biological and pharmacological activities (Marin et al 2018)

Summary

Introduction

Mastitis is one of the most important health problem in dairy sheep worldwide. Clinical mastitis incidence during lactation is usually less than 5%, but, in some cases, it can reach or overcome 30% (Contreras et al 2007). Scienze Fisiche e Naturali (2021) 32:407–416 aureus and coagulase-negative staphylococci (CoNS) are considered, respectively, as the main pathogens involved in clinical and subclinical mastitis in sheep (Bergonier et al 2003; Mork et al 2005; Contreras et al 2007). The antibacterial activity has been attributed to the presence of oxygenated monoterpenes, especially thymol and carvacrol in synergy with its precursor p-cymene (Jarić et al 2015; Tepe and Cilkiz 2016). These compounds showed to be effective against S. aureus and CoNS (Hyldgaard et al 2012; dos Santos Rodrigues et al 2017; Gaio et al 2017)

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