Introduction
Over the past two decades, the rise in antimicrobial resistance among
pathogenic bacteria has significantly contributed to the persistence of
various bacterial infections in the human body
(Mah,
2012;Borges et al., 2015). The current research on antimicrobials in the
medical field has confirmed the widespread occurrence of antimicrobial
resistance, leading to a crisis in antimicrobial resistance (1, 2) . In
dentistry, the commonly used local disinfectant chlorhexidine (CHX) not
only exhibits toxic effects on host cells but also possesses the ability
to promote antimicrobial resistance through mechanisms such as bacterial
membrane alteration, resistance genes, and multidrug efflux pumps (3,
4). Another challenge in combating oral biofilms, which are up to 1000
times less susceptible to conventional antimicrobial agents compared to
their planktonic counterparts, is the eradication of bacteria residing
in the deep layers of these biofilms (5,
6).
In the oral cavity, there are approximately 700 known bacterial species
that colonize various surfaces, including the gingiva, teeth, and other
oral mucosal sites (7). These bacteria form highly organized microbial
communities called biofilms, which provide them with significant
protection against antimicrobial agents. The biofilm structure hinders
the diffusion of antimicrobial agents (8), and the deepest layers of the
biofilm have reduced oxygen levels and a low rate of cell division (9).
During the formation of oral biofilms, the initial attachment occurs on
the pellicle, a layer primarily composed of salivary proteins. Early
colonizers, such as Streptococcus spp., Actinomyces spp.,Veillonella spp., and Neisseria spp., adhere to the
pellicle (10, 11). Subsequently, Fusobacterium nucleatum creates
a microenvironment with reduced oxygen levels, favoring the adhesion of
strict anaerobic pathogens, including late colonizers such asAggregatibacter actinomycetemcomitans , Porphyromonas
gingivalis , and Prevotella intermedia (12).
Mediterranean plants have been extensively studied as valuable natural
resources for medicinal purposes (13). Over time, numerous biochemical
compounds derived from these plants have been identified (14). Further
investigations into developing plant-derived antibiotics have
highlighted the antimicrobial properties of various compounds, including
phenolic acids, flavonoids, plant peptides, phenanthrenes, and terpenes
(15-18). Plant metabolites such as phenolics, terpenoids,
sulfur-containing compounds, coumarins, quinones, and alkaloids have
shown significant biological activity as anti-biofilm agents and
inhibitors of quorum sensing (19).
Regional plant products are utilized worldwide, particularly in
impoverished nations where they serve as the most affordable form of
medicine. However, it is crucial to optimize their formulation and
development by targeting specific molecular mechanisms (20). These plant
products have the potential to enhance oral health (21) and overall
systemic well-being. Several plant-based products have been utilized in
oral healthcare and medicinal formulations to combat dental caries,
periodontitis, and gingivitis (22). The treatment of pathogenic
microbes, which pose significant challenges due to their pathogenicity
and resistance, can be improved by targeting them when they are more
susceptible to alternative natural antibiotics (23). Considering the
complexity of polymicrobial interactions and the intricate compositions
of plant-derived products, it is crucial to conduct further research on
additional plant species, extraction methods, and explore the
synergistic effects of different compounds. Urgent investigation in
these areas is necessary.
The objective of this report was to investigate the antimicrobial
activity of various Mediterranean herb extracts against different
microorganisms. Specifically, the ethyl acetate extracts ofAchillea taygetea , Cistus creticus , Cistus
monspeliensis , Lavandula stoechas , Mentha aquatica ,Mentha longifolia , Origanum vulgare , Phlomis
cretica , Rosmarinus officinalis , Salvia sclarea ,Satureja parnassica , Satureja thymbra , Sideritis
euboea , Sideritis syriaca , Stachys spinosa , andThymus longicaulis were tested against eight common oral
pathogenic bacteria and the fungus Candida albicans .
Additionally, two reference strains, Staphylococcus aureus andEscherichia coli , which are found on the skin and intestinal
mucosa, respectively, were included in the study.
The null hypothesis states that the aforementioned extracts do not
exhibit any antimicrobial effects on the tested microbial species. To
test this hypothesis, three antimicrobial assays were conducted: the
minimal inhibitory concentration (MIC) assay, the minimal bactericidal
concentration (MBC) assay, and the biofilm plate assay.