Research paperCombined treatment of Thymus vulgaris L., Rosmarinus officinalis L. and Myrtus communis L. essential oils against Salmonella typhimurium: Optimization of antibacterial activity by mixture design methodology
Graphical abstract
Introduction
The vast majority of reported cases of food poisoning are caused by eating food contaminated with pathogenic microorganisms [1]. For this alarming situation, the identification and evaluation of adequate procedures to control pathogens and ensure the safety of food products have become one of the biggest challenges today [2]. To decrease economic losses in health hazards due to pathogenic bacteria, the use of natural products as antibacterial compounds has become common [3]. In this way, very important antimicrobial activities against a large number of pathogenic bacteria were reported for many natural compounds such as extracts from herbs and fruit extracts [4]. For their antimicrobial properties, a wide variety of plants have been assessed [5] and reviewed [6], [7], [8]. EOs and other plant extracts have been considered as alternatives to treat diseases and infectious agents and to favorite food preservation [9], [10]. Furthermore, enhancing food preservation and getting a balance between the sensory acceptability and antimicrobial efficacy is actually possible by the addition of small amounts of natural preservatives such as EOs [4].
T. vulgaris L., R. officinalis L. and M. communis L. are amid the most popular species used throughout the world. Indeed, T. vulgaris L. (thyme) is a member of the Lamiaceae family and its EO is characterized by phenolic compounds, such as thymol and carvacrol [11] and of hydrocarbons, such as γ-terpinene and p-cymene [8]. Furthermore, its antibacterial activity was largely confirmed [12], [13]. R. officinalis L. (rosemary) is also a common characteristic of the Mediterranean flora belonging to the Lamiaceae family. The reported components of its EO were monoterpenes such as α-pinene, 1,8-cineole and camphor [14] and its EO antimicrobial activity was previously demonstrated by many researchers [14], [15]. M. communis L. (myrtle) is an evergreen shrub belonging to the family of Myrtaceae growing spontaneously in Mediterranean forests [16]. According to the amounts of myrtenyl acetate, the EO of this species can be separated into two major groups. Moreover, and with regard to the relative ratio of α-pinene to myrtenyl acetate or α-pinene to 1,8-cineole, each group can be divided into two subgroups, [17]. Several authors have previously confirmed the antibacterial activity of M. communis L. EO [18], [19].
Salmonella is the most commonly reported source of food poisoning around the world. This Gram-negative, facultatively anaerobic, non-spore-forming bacilli can be split into more than 2000 serotypes [20]. Salmonella typhimurium (S. typhimurium) is an important cause of food poisoning and salmonellosis. It is, no doubt, one of the most common illnesses in the developing countries [21]. It is classed as typhoidal salmonella [22] and its infections through the ingestion of contaminated water or foods are common [23]. The antibacterial activity of the studied EOs against S. typhimurium strain was previously reported for T. vulgaris L. [24], R. officinalis L. [25] and M. communis L. [26].
Several authors have reported and reviewed the synergistic activity of EOs in combination with antibiotics to minimize the side effects of these latters [27], [28]. Other authors have focused on the synergistic effects of EOs combinations to obtain effective antimicrobial activity at satisfactorily low concentrations and consequently, reduce the negative sensory impact [29], [30]. The synergism between EOs against pathogen strains was previously evaluated by different techniques such as checkerboard method, time-kill method and E-test [27]. In this article, we have developed formulations from the three studied EOs in order to increase the sensitivity of S. typhimurium. For this, we have tried an experimental design (Mixture designs) in the disc diffusion method to highlight the synergy between EOs and the checkerboard method to confirm this synergy. Using mixture design in the disc diffusion method has permitted us to find the combination area leading to the increase of S. typhimurium sensitivity. The sensitivity to the different antimicrobial agents was classified by the diameter of the inhibition zone as follows: not sensitive, diameters less than 8 mm; sensitive, diameters 9–14 mm; very sensitive, diameters 15–19 mm; and extremely sensitive, diameters larger than 20 mm [31]. The increase in sensitivity was manifested by an increase in the diameter of inhibition from an interval where the strain is classified as sensitive to another one where the strain is classified as very sensitive.
Section snippets
Plant material and EOs extraction
The aerial parts of T. vulgaris L., R. officinalis and M. communis L. were collected from the National Institute of Medicinal and Aromatic Plants in Taounate (Morocco) (latitude 34°29′59.4″N; longitude 4°48′16.6″W). The harvest and the distillation of T. vulgaris L. and R. officinalis were carried out in the middle of July because this is the best period for better exploiting the thyme [32] and the rosemary essences [33]. Concerning M. communis L., it was harvested and distilled in October
Essential oils yield and chemical composition
The results of plants distillation have indicated that the essential oil yield was 1.9%, 2.3% and 0.68% for T. vulgaris L., R. officinalis and M. communis, respectively. The chemical composition results of T. vulgaris L., R. officinalis and M. communis L. EOs obtained by GC and GC/MS analysis are presented in Table 1. Forty-six constituents, which represented 97.47%, 98.88% and 99.96% of the total of T. vulgaris L., R. officinalis and M. communis L EOs, respectively, were identified. T. vulgaris
Conclusion
In summary, these results showed that T. vulgaris L., R. officinalis L. and M. communis L. EOs alone or combined are effective against S. typhimurium. The screening of antimicrobial activity of the three studied EOs allowed us, firstly, to confirm the highest antibacterial activity of thyme EO followed by myrtle EO against a lower antibacterial activity of rosemary EO. Secondly, a great potential of T. vulgaris L. and M. communis L. EOs was observed in combined treatments by mixtures designs
References (61)
- et al.
Inhibitory effects of selected plant essential oils on the growth of four pathogenic bacteria: E. coli O157:H7, Salmonella Typhimurium, Staphylococcus aureus and Listeria monocytogenes
Food Control
(2007) - et al.
A study of the synergistic antilisterial effects of a sub-lethal dose of lactic acid and essential oils from Thymus vulgaris L., Rosmarinus officinalis L. and Origanum vulgare L
Food Chem.
(2007) - et al.
Biological effects of essential oils-a review
Food Chem. Toxicol.
(2008) - et al.
Plants belonging to the genus Thymus as antibacterial agents: from farm to pharmacy
Food Chem.
(2015) - et al.
Chemical composition, antimicrobial, antioxidant and antitumor activity of Thymus serpyllum L., Thymus algeriensis Boiss and Reut and Thymus vulgaris L. essential oils
Ind. Crops Prod.
(2014) - et al.
Essential oils composition in two Rosmarinus officinalis L. varieties and incidence for antimicrobial and antioxidant activities
Food Chem. Toxicol.
(2010) - et al.
Biochemical activities of Iranian Mentha piperita L. and Myrtus communis L. essential oils
Phytochemistry
(2006) - et al.
Magnetic nano-beads based separation combined with propidium monoazide treatment and multiplex PCR assay for simultaneous detection of viable Salmonella Typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes in food products
Food Microbiol.
(2013) - et al.
Analysis of the Salmonella typhimurium isolates from food-poisoning cases by molecular subtyping methods
Food Microbiol.
(2000) - et al.
Antimicrobial activity and chemical composition of Thymus vulgaris, Thymus zygis and Thymus hyemalis essential oils
Food Control.
(2008)
Effect of bioclimatic area on the essential oil composition and antibacterial activity of Rosmarinus officinalis L
Food Control
Efficacy of myrtle oil against Salmonella Typhimurium on fresh produce
Int. J. Food Microbiol.
Combinations of food antimicrobials at low levels to inhibit the growth of Salmonella sv. Typhimurium: a synergistic effect?
Food Microbiol.
Antimicrobial activity of plant essential oils using food model media: efficacy, synergistic potential and interactions with food components
Food Microbiol.
Antimicrobial activity of essential oils on the native microflora of organic Swiss chard
LWT- Food Sci. Technol.
Effects of spacing and harvesting time on herbage yield and quality/quantity of oil in thyme, Thymus vulgaris L
Ind. Crops Prod.
Apparatus for the determination of volatile oil
J. Am. Pharm. Assoc.
Synergistic antibacterial activity between Thymus vulgaris and Pimpinella anisum essential oils and methanol extracts
J. Ethnopharmacol.
A cross mixture design to optimise the formulation of a ground waste glass blended cement
Constr. Build. Mater.
Mix design of concrete with high content of mineral additions: Optimisation to improve early age strength
Cem. Concr. Compos.
Factorial design applied to concentrate bioactive component of Cymbopogon citratus essential oil using short path distillation
Chem. Eng. Res. Des.
The effects of thyme (Thymus vulgaris) and rosemary (Rosmarinus officinalis) essential oils on Brochothrix thermosphacta and on the shelf life of beef packaged in high-oxygen modified atmosphere
Food Microbiol.
Antimicrobial activity of the essential oils of Thymus vulgaris L. measured using a bioimpedometric method
J. Food Prot.
Essential oils: their antibacterial properties and potential applications in foods–a review
Int. J. Food Microbiol.
Microbial Food Poisoning
Chemical composition and antioxidant properties of Laurus nobilis L. and Myrtus communis L. essential oils from Morocco and evaluation of their antimicrobial activity acting alone or in combined processes for food preservation
J. Sci. Food Agric.
Bioactivity of selected plant essential oils against Listeria monocytogenes
J. Appl. Microbiol.
Antimicrobial activity of essential oils and other plant extracts
J. Appl. Microbiol.
Antimicrobial agents from plants: antibacterial activity of plant volatile oils
J. Appl. Microbiol.
Comparative study on the antiviral activity of selected monoterpenes derived from essential oils
Phytother. Res.
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