Original Article

Journal of Evidence-Based
Complementary & Alternative Medicine
In Vitro Antimicrobial Activity of Thymus 1-7
ª The Author(s) 2017

vulgaris Essential Oil Against Major Oral Reprints and permission:

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DOI: 10.1177/2156587217700772
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Mohammadmehdi Fani, DMD, MSc1 and Jamshid Kohanteb, PhD1

Abstract
The objective of present investigation was to determine antimicrobial activity of Thymus vulgaris oil on some oral pathogens.
Thymus vulgaris oil was prepared by hydrodistillation and tested against 30 clinical isolates of each of Streptococcus pyogenes,
Streptococcus mutans, Candida albicans, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans, prepared from related
oral infections using agar disk diffusion and broth microdilution methods. Thymus vulgaris oil at concentrations of 16 to 256 mg/mL
exhibited strong inhibitory activity on all clinical isolates producing inhibition zones of 7.5 to 42 mm as measured by agar disk
diffusion method. Streptococcus pyogenes and Streptococcus mutans were the most sensitive isolates with minimum inhibitory
concentrations of 1.9 and 3.6 mg/mL, respectively. The minimum inhibitory concentration values for C albicans, A actinomyce-
temcomitans, and P gingivalis were 16.3, 32, and 32 mg/mL, respectively.

Keywords
Streptococcus pyogenes, Candida albicans, Thymus vulgaris

Received June 20, 2016. Received revised February 9, 2017. Accepted for publication February 18, 2017.

Thymus vulgaris is a species of ever green plant in the Lamia- in the essential oil are thymol methyl ether, cineol, cymene,
ceae family originated from Mediterranean regions and has a-pinene, and borneol.10,12 The antimicrobial activities of
been adapted to many different climates around the world. It Thymus vulgaris oil is mostly believed to be related to the
is a bushy, woody based shrub, 10 to 40 cm high with small and thymol and carvacrol contents of the oil.
highly aromatic gray-green oval leaves containing numerous Dental caries, periodontal diseases, and streptococcal phar-
small glands with clusters of pink or purple flowers. The genus yngitis are the most common oral infectious diseases of man.
Thymus comprises approximately 400 species, several of which Dental caries is a multifactorial condition in which diet, nutri-
are widely used in traditional medicine.1,2 Thymus vulgaris is tion, resident microbial oral flora, and the host responses inter-
the most important species and traditionally has been adminis- act to determine whether infection occurs. Streptococcus
tered for whooping cough, bronchitis, laryngitis gastritis, upper mutans and Streptococcus sobrinus are known as the main
respiratory congestion, and diarrhea. Thymus vulgaris leaves etiological agents of dental caries. These endogenous cario-
oil or extract has also been used in the treatment of sore throat, genic bacteria adhere and colonize the tooth surface and pro-
tonsillitis, gum diseases, rheumatism, and arthritis.3-5 This duce a sticky glycocalyx film composed of glucan resulting
essential oil has been considered as an antiseptic, antimicrobial, from the action of Streptococcal glucosyl transferase on dietary
antispasmodic, antioxidant, and antitussive agent. There have carbohydrates (mainly sucrose). Accumulation of bacteria on
been a number of reports validating the in vitro antibacterial the enamel causes dental plaques formation within which there
and antifungal activities of this essential oil on some human is continuing acid production by bacterial plaques, which
pathogens, including Staphylococcus aureus, Pseudomonas
aeruginosa, Escherichia coli, Candida albicans, Mycobacter-
1
ium smegmatis, Proteus mirabilis, Propionebacterium acnes, Shiraz University of Medical Science, Shiraz, Iran
and Salmonella species.6-11 The main constituents of Thymus
Corresponding Author:
vulgaris leaves essential oil are 2 phenolic compounds, thymol Mohammadmehdi Fani, Department of Oral Medicine, School of Dentistry,
(2-isopropyl-5-methylphenol) and its conformational isomer, Shiraz, Iran.
carvacrol (5-isopropyl-2-methylphenol). Further components Email: fanim@sums.ac.ir

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2 Journal of Evidence-Based Complementary & Alternative Medicine

causes demineralization of enamel and consequently leads to (for easy diffusion) and used as stock solution for determination of
caries formation.13 antimicrobial activities of this oil.
Periodontitis is a chronic, slowly progressive polymicrobial
infectious disease that affects the entire tooth and supporting Isolation of Streptococcus pyogenes (b-Hemolytic
tissues. In this infection, the gingival crevice enlarges to
become a “pocket” with local inflammation. Periodontal dis-
Streptococci Group A)
ease is characterized by destruction of periodontal ligaments, Suspected patients with pharyngitis, mostly children below 10 years of
alveolar bone, and gingival pocket formation, which conse- age, were examined, and exudates were obtained from the posterior part
quently leads to tooth loss. This infection is known to be caused of the pharynx using sterile cotton swabs. The swabs were then cultured
on sheep blood agar (SBA) plates and kept at 37 C, 5% CO2, for 48
by Aggregatibacter actinomycetemcomitans, Prevotella inter-
hours. The suspicious colonies with b-hemolysis were subjected to the
media, Porphyromonas gingivalis, and Tannerlla forythus,
bacitracin sensitivity test by using a 0.04 mg disk for identification of S
which are frequently isolated from gingival pocket and subgin- pyogenes. Pure cultures of each strain isolated from the patients were
gival plaques of patients with periodontitis.14 obtained on sheep blood agar plates and kept at 4 C until used.21
Streptococcal pharyngitis is a bacterial infection of orophar-
ynx that affects tonsils and possibly larynx and characterized
by fever, sore throat, cervical lymphadenopathy, and tonsillar Isolation of Streptococcus mutans From Carious Teeth
exudates. This infection is caused by Group A, b-hemolytic Streptococcus mutans was isolated from carious teeth as described
Streptococci or Streptococcus pyogenes. Although untreated previously.21-23 Briefly, the extracted carious teeth were incubated
Streptococcal pharyngitis usually resolves within a few days, in 10 mL Todd-Hewitt Broth (THB) (Merck, Germany) at 37 C, 5%
antibiotic treatment will shorten the acute illness by about 16 CO2, for 48 hours. A Mitis-Salivarious-Bacitracin-Agar (MSBA) was
hours, and hence reduce the risk of post–streptococcal pharyn- subcultured from THB and incubated at 37 C, 5% CO2, for 72 hours. S
gitis complications such as rheumatic fever and glomerulone- mutans was identified by standard bacteriological and biochemical
phritis. Although penicillin has long been regarded as the procedures, including colony morphology (greenish hemolysis), cata-
lase, Voges-Proskauer, arginine dihydrolase, hippurate hydrolysis,
treatment of choice in tonsillopharyngitis caused by S pyo-
and fermentation of glucose, manitol, raffinose, melobiose, and sorbi-
genes, since late 1970, bacteriological and clinical failure rate tol.23-25 Pure culture of each clinical isolate of S mutans was obtained
with penicillin therapy begun to increase, ranging from 2% to on MSBA medium and kept at 4 C until used.
30% among these patients and asymptomatic carriers.15-18 Ery-
thromycin and related macrolide antibiotics are considered as
an alternative among patients with allergy to penicillin.19 How- Isolation of Periodontopathic Bacteria
ever, increasing incidence of erythromycin resistance has also Patients with either aggressive or localized aggressive periodontitis
been reported in several parts of the world.20 It is therefore were examined and sampled for isolation of A actinomycetemcomitans
essential to discover new antibacterial agents to combat strains and P gingivalis.21,22,26 Subgingival pocket samples were taken from
expressing resistance to available antibiotics. the deepest part of periodontal pocket (probing depth 6 mm) by
Although the in vitro antimicrobial activity of Thymus insertion of sterile paper point (Iso 35, Bocht, Offenburg, Germany).
vulgaris leaves essential oil on some human pathogens are Each sample was inoculated into 4 mL Trypticase Soy Broth (TSB)
widely documented, the effects of this oil on oral pathogens containing 5 mg/mL of hemin and menadione (Becton Dickinson
Microbiology System) and kept under anaerobic condition at 37 C,
such as periodontopathic and cariogenic microorganisms are
5% CO2, for 48 hours. Bacteria from TSB were subcultured on Trypti-
not fully understood. In the present study, we are reporting in case Soy-Blood Agar (TSBA) plates (composed of 40 g/L Trypticase
vitro inhibitory activity of Thymus vulgaris oil on some clinical soy agar, 5 mg/L hemin,10 mg/L N-acetylmuramic, acid and 50 mL/L
isolates of oral pathogens, including Streptococcus pyogenes, defibrinated sheep blood) and kept under anaerobic condition at 37 C,
Streptococcus mutans, Candida albicans, Aggregatibacter 5% CO2, for 72 hours. A actinomycetemcomitans and P gingivalis
actinomycetemcomitans, and Porphyromonas gingivalis. were identified according to our previous publications.21,22,26 Pure
culture of each clinical isolates was prepared on TSBA and kept at
4 C until used.
Materials and Methods
Preparation of Thymus vulgaris Oil Isolation of Candida albicans
Fresh Thymus vulgaris were purchased from the local market and were Patients with denture stomatitis, oral candidiasis, and infected root
kept in dark at room temperature. One hundred grams of dried leaves canal were sampled and cultured on Sabouraud dextrose agar
was crashed and extracted by conventional steam distillation using a (SDA) and kept at 37 C for 72 hours. C albicans was diagnosed
Clevenger apparatus for 3 hours, and condensation took place con- on the basis of colonial morphology and other conventional myco-
tinuously at 4 C in cold water. The essential oil was then dried over logical procedures.10,21 Pure cultures of C albicans were prepared
sodium sulfate (Sigma-Aldrich, St Quentin-Fallaveier, France) and on SDA and kept at 4 C until used. In the present study, 30 strains
stored at 4 C in dark vials until used. The aforementioned experiment of each of S mutans, A actinomycetemcomitans, P gingivalis,
was repeated 3 times and the mean of the yield + standard deviation C albicans, and S pyogenes isolated from patients with various
was recorded. A 1 mg/mL solution of Thymus vulgaris oil was pre- oral infections were used for Thymus vulgaris oil antimicrobial
pared in 10% aqueous dimethyl sulfoxide containing 0.5% Tween 80 determination by standard assays.
Fani and Kohanteb 3

Table 1. Antimicrobial Activity of Thymus vulgaris Oil on Some Clinically Isolated Oral Pathogens by Agar Disk Diffusion Testsa.

Aggregatibacter
Thymus vulgaris Streptococcus pyogenes Streptococcus mutans Candida albicans Porphyromonas gingivalis actinomycetemcomitans
Oil (mg/mL) (n ¼ 30) (n ¼ 30) (n ¼ 30) (n ¼ 30) (n ¼ 30)

256 42 + 0.8 (100%) 38.1 + 1 (100%) 37.4 + 1 (100%) 29.9 + 0.8 (100%) 32.7 + 0.7 (100%)
128 29.4 + 0.8 (100%) 29.2 + 1 (100%) 29.8 + 0.7 (100%) 16.9 + 0.8 (100%) 24.4 + 0.7 (100%)
64 21.1 + 0.8 (100%) 18.9 + 1 (100%) 18.3 + 0.7 (100%) 9.5 + 0.5 (100%) 16.7 + 1 (100%)
32 12.7 + 1.3 (100%) 11.7 + 1 (100%) 10.5 + 0.7 (100%) 8.2 + 0.4 (40%) 10.9 + 0.9 (60%)
16 9.6 + 0.8 (100%) 9.1 + 0.6 (76.6%) 8.7 + 0.6 (36.6%) 7.5 + 0 (16.6%) 8+ 0.7 (26.6%)
8 8.8 + 0.8 (80%) 8 + 0.2 (50%) 0+ 0 (0%) 0+ 0 (0%) 0+ 0 (0%)
4 8.1 + 0.3 (26.6%) 0 + 0 (0%) 0+ 0 (0%) 0+ 0 (0%) 0+ 0 (0%)
2 R R R R R
Vancomycin 21.5 + 0.8 21.2 + 0.9 R R R
Amikacin R R R 9.8 + 0.7 9.1 + 0.2
Nystatin R R 18. + 0.8 R R
10% DMSO R R R R R
Abbreviations: R, resistance (no inhibition zone); DMSO, dimethyl sulfoxide. Vancomycin disk (30 mg), amikacin disk (30 mg), nystatin disk (25 mg).
a
Data presented are inhibition zone diameter in mm (Mean + SD). The values in parentheses are sensitivity percentages.

Agar Disk Diffusion A actinomycetemcomitans and P gingivalis. Cell suspensions of the

clinical isolates were prepared in the appropriate liquid culture media
The antibacterial activities of Thymus vulgaris oil were determined by and their concentrations were adjusted to 107 colony forming units/
the standard disk diffusion susceptibility test on solid media. MSBA mL. Two-fold dilutions of Thymus vulgaris oil were prepared from the
plates were used for S mutans, SBA plates for S pyogenes, SDA for C stock solution. Aliquots (100 mL) of each dilution of Thymus vulgaris
albicans, and TSBA for A actinomycetemcomitans and P gingivalis. S oil were dispensed in 96-well cell culture plates. One hundred micro-
mutans ATCC 25175, A actinomycetemcomitans ATCC 29523, strains liters of each bacterial suspension was added to each well and incu-
which were maintained anaerobically on TSBA supplemented with bated under anaerobic conditions at 37 C, 5% CO2, for 48 hours.
10% defibrinated horse blood and hemin (5 mg/mL; Wako Pure Chem- Microplates containing C albicans were incubated under aerobic
ical Industries, Osaka, Japan), and C albicans ATCC10231 were used condition at 37 C for 48 hours. The absorbance was then measured
as control. at 595 nm and the highest dilution at which no growth (OD  0.05)
Pure microbial cell suspensions of each clinical isolates were observed was defined as the minimum inhibitory concentration. All
obtained in 5 mL THB for S mutans and S pyogenes, TSB for A experiments were done in triplicates, and means + standard devia-
actinomycetemcomitans and P gingivalis, and Sabouraud dextrose tions were recorded.
broth (SDB) for C albicans. The suspension turbidity of these micro-
organisms was adjusted to 1.5  108 colony forming unit/mL (# 0.5
McFarland) and 100 mL of this suspension was seeded on appropriate Statistical Analysis
solid culture media. A 6-mm-diameter sterile Whatman filter paper Statistical analysis was performed by the w2 and Fisher’s exact tests
No. 5 (round filter Machery-Nagel, Doren, Germany) was impreg- using the SPSS software package, version 11.5.
nated with 50 mL of various concentrations of Thymus vulgaris oil
and placed on the aforementioned culture media, followed by incu-
bation at 37 C for 72 hours. Sabouraud dextrose agar containing C
albicans was incubated at 37 C for 72 hours. The growth inhibition Results
zones around the filter paper were measured in millimeters; means The average yield of Thymus vulgaris essential oil on the basis
and standard deviations were calculated and recorded. Those disks of 3 successive extractions by hydrodistillation was 1.6 + 0.34
containing Thymus vulgaris oil that did not produced inhibition
g oil/100 g dried leaves. The oil was clear light yellow with
zones were considered negative results. Sterile filter paper soaked
pleasant odor. The results of agar disk diffusion assay regard-
in 50 mL of 10% dimethyl sulfoxide and antibiotic disks of vanco-
mycin (30 mg), amikacin (30 mg), and nystatin (25 mg) were also used ing the growth inhibition zones (mean + standard deviation) of
as control. the tested isolates against various concentrations (256 to
2 mg/mL) of Thymus vulgaris oil are summarized in Table 1.
In this test, inhibition zones above 6 mm in diameter were taken
Determination of Minimum Inhibitory Concentration as positive results. At the concentrations of 64 to 256 mg/mL,
of Thymus vulgaris Oil all (100%) the microbial isolates were found sensitive and
produced inhibition zones ranging from 7.5 + 0 to 42 +
The minimum inhibitory concentration of Thymus vulgaris oil
against bacterial and fungal (C albicans) isolates from oral infections 0.8 mm in diameter. S pyogenes was the most sensitive isolate
was carried out by broth microdilution method using 96-well cell since all (100%) of these clinical isolates produced the widest
culture plates27 (Greiner Bio-One, Bergamo Italy). Todd-Hewitt inhibition zones against all Thymus vulgaris oil concentrations
Broth was used for S mutans and S pyogenes, SDB broth for C (4-256 mg/mL). On the other hand, all strains (100%) of
albicans, and TSB containing hemin and menadione (5 mg/mL) for S pyogenes (n ¼ 30), S mutans (n ¼ 30), and C albicans
4 Journal of Evidence-Based Complementary & Alternative Medicine

Figure 1. Agar disk diffusion tests showing inhibition zone around disk containing various concentrations of Thymus vulgaris extract.

Table 2. Minimum Inhibitory Concentration of Thymus vulgaris Oil on Some Clinically Isolated Oral Pathogens by Broth Microdilution Methoda.

Aggregatibacter
Streptococcus pyogenes Streptococcus mutans Candida albicans Porphyromonas gingivalis actinomycetemcomitans
Antimicrobials (n ¼ 30) (n ¼ 30) (n ¼ 30) (n ¼ 30) (n ¼ 30)

TVO 3.6 + 0.9 1.9 + 0.2 16.3 + 4 32 + 0 32 + 0

Vancomycin 0.95 + 0.5 0.66 + 0.2 R R R
Amikacin R R R 29.1 + 1.9 24.1 + 1.8
Nystatin R R 15 + 1.7 R R
10% DMSO R R R R R
Abbreviations: TVO, Thymus vulgaris oil; R, resistance; DMSO, dimethyl sulfoxide.
a
Data presented are minimum inhibitory concentration in mg/mL (mean + SD).

(n ¼ 30) were sensitive to the 32 mg/mL dose of Thymus S pyogenes, S mutans, C albicans, A actinomycetemcomitans,
vulgaris oil, producing inhibition zones ranging from 10.5 to and P gingivalis as measured by agar disk diffusion and broth
12.7 mm, while 40% (12/30) of P gingivalis and 60% (18/30) microdilution methods. S pyogenes isolated from patients with
of A actinomycetemcomitans were sensitive to this oil concen- pharyngitis were the most sensitive strains to Thymus vulgaris
tration. None of the clinical isolates in this study showed inhi- oil as they produced the widest growth inhibition zones
bition zones against 2 mg/mL or lower concentration of Thymus (42 + 0.8 mm) and lowest minimum inhibitory concentration
vulgaris oil. Agar disk diffusion test carried out on 10% (1.9 + 0.2 mg/mL). Sfeir et al28 using the same techniques found
dimethyl sulfoxide showed no inhibitory activity on oral patho- S pyogenes highly sensitive to Thymus vulgaris oil with growth
gens used in this study (Figure 1). The results of minimum inhibition zone of 38 mm and minimum inhibitory concentration
inhibitory concentrations of Thymus vulgaris oil as measured as low as 0.87 mg/mL. The antimicrobial activity of various
by broth microdilution method are summarized in Table 2. thymus species essential oils on oral Streptococci were docu-
S pyogenes with the minimum inhibitory concentration mented by Nikolic et al.10 Thymus serpyllum oil showed stron-
1.9 + 0.2 mg/mL followed by S mutans with minimum inhibi- gest activity against S pyogenes clinical isolates with minimum
tory concentration 3.6 + 0.9 mg/mL were the most sensitive inhibitory concentration of 2.5 + 0.23 mg/mL, while Thymus
microorganism tested. The minimum inhibitory concentration vulgaris oil exhibited lower activity against S pyogenes with
of Thymus vulgaris oil on C albicans, P gingivalis, and A minimum inhibitory concentration of 80 mg/mL.10 Moreover,
actinomycetemcomitans isolates were 16.3 + 4, 32 + 0, and these investigators have reported stronger activity of T serpyllum
32 + 0 mg/mL, respectively. Thymus vulgaris oil minimum oil than streptomycin and ampicillin against S pyogenes as mea-
inhibitory concentration on standard strains of S mutans sured by minimum inhibitory concentration determinations.
(ATCC 25175), C albicans (ATCC 10231), and A actinomyce- Solano et al29 reported that S pyogenes isolates produced wider
temcomitans (ATCC 29523) were 16 + 0, 32 + 0, and growth inhibition zones (34 mm) against Thymus vulgaris oil
32 + 0 mg/mL, respectively. versus 6-unit penicillin disk, which produced 24 mm inhibition
zones. In vitro antibacterial activity of Thymus vulgaris vapor
against S pyogenes is also documented.30 Considering the strong
Discussion inhibitory activity of Thymus vulgaris oil against S pyogenes as
Data presented in this study revealed strong inhibitory activity presented in our study and others,10,28-30 it seems reasonable to
of Thymus vulgaris oil on some oral pathogens, including use this essential oil in aromatherapy, particularly among
Fani and Kohanteb 5

patients with respiratory tract infections caused by S pyogenes activities of Thymus vulgaris oil appear to be associated with
such as tonsillitis, pharyngitis, sinusitis, and bronchitis. the phenolic compounds thymol and carvacrol.38 Although the
Ghorab et al2 reported that incubation of S mutans, the main mode of action of these compounds are not clearly understood,
etiologic agent of dental caries, with 20% Thymus vulgaris oil it is mostly believed that the hydroxyl group on these 2 com-
resulted in 96% growth inhibition of this bacteria after pounds interacts with the cytoplasmic membrane, changes
48 hours. Moreover, significant reduction of S mutans adher- its permeability, and affects the lipid ordering and stability of
ence to buccal epithelial cells after mouth washing with 20% its bilayer, resulting in an increase of proton passive flux across
Thymus vulgaris oil has been observed.31 Nikolic et al10 found the membrane, leading to disruption of cytoplasmic membrane
Thymus vulgaris oil less effective against S mutans than and leakage of cellular contents.38-42 The antifungal activity of
Thymus serpyllum, as this oil revealed higher minimum inhi- the oil is mostly associated with the direct interaction of thy-
bitory concentration (160 + 4.61 mg/mL). Data presented in mol, carvacrol, and P-cymene with cytoplasmic membrane
our study exhibit strong inhibitory activity of Thymus vulgaris ergostrol, which consequently leads to fungal cell membrane
oil with minimum inhibitory concentration of 3.6 + 0.9 mg/mL disruption and release of the cellular contents.8,12 Most studies
on S mutans clinical isolates. On the contrary, Babpour et al32 reporting the antimicrobial activity of plant essential oils
have detected no inhibitory effects of methanolic and aqueous against foodborne and human pathogens agree that essential
Thymus vulgaris extract on S mutans even at concentrations oils are relatively more active against gram positive than gram
over 500 mg/mL. Very weak inhibitory activity of Thymus negative bacteria.43 Results obtained in our study showed gram
vulgaris oil with minimum inhibitory concentration of 2670 positive bacteria were more susceptible to Thymus vulgaris oil
mg/mL on oral Streptococci were also reported by Imelouane than the gram negatives as measured by agar disk diffusion and
et al.9 Thymus vulgaris oil analysis by gas chromatography- minimum inhibitory concentration determinations. Zaika
mass spectrometry carried out by these investigators exhibited et al44 proposed that gram positive bacteria were more resistant
no carvacrol and presence of very low amount of thymol to the plant volatile oils than to the gram negatives. This is in
(0.24%). These 2 phenolic compounds play major roles in bac- contrast to the hypothesis proposed by Dean et al,45 who
terial growth inhibition, and therefore, these findings may be an observed little or no differences between gram positive and
explanation for the weak (high value of minimum inhibitory gram negative bacteria regarding the inhibitory effects of plant
concentration) or no inhibitory activity of Thymus vulgaris oil essential oils. However, greater susceptibility of gram nega-
on oral Streptococci as reported by the investigators.9 Denture- tives against Thymus vulgaris oil than the gram positive bac-
related stomatitis is a very common form of oral candidiasis teria is documented.9 The greater resistance of gram negatives
and is referred to as mild inflammation and erythema of might be associated with the presence of an outer membrane
mucosa beneath a denture. In our study C albicans isolated hydrophilic lipopolysaccharide, which inhibits accumulation
from patients with denture stomatitis (21/30) and infected root of hydrophobic plant essential oil on the cell membrane.46 Con-
canal from patients with advanced periodontitis (9/30) were all sumption of Thymus vulgaris flowers and leaves are safe; how-
sensitive to Thymus vulgaris oil with mean minimum inhibitory ever, caution is warranted with the use of thyme oil, which
concentration of 16.3 + 4 mg/mL. Minimum inhibitory con- should not be taken orally and should be diluted with a suitable
centrations values of the oil as low as 1.62 + 0 mg/mL3 to as oil (olive or almond oil) before use. Side effects of thyme oil if
high as 3300 mg/mL5 for clinical isolates of C albicans are taken orally may include headache, dizziness, low blood pres-
documented by other investigators. Aggregatibacter actinomy- sure, gastrointestinal irritation, nausea, vomiting, and diarrhea.47
cetemcomitans and Porphyromonas gingivalis are the 2 anae- Data presented in this study revealed strong in vitro antimi-
robic gram negative rods that are the most prevalent etiological crobial activity of Thymus vulgaris oil on clinical isolates of
agents of periodontal diseases. Data on the inhibitory activity S pyogenes, S mutans, C albicans, A actinomycetemcomitans,
of Thymus vulgaris oil on these periodontopathic bacteria are and P gingivalis and therefore might be used in mouth rinse,
very limited in the literature. In our study, A actinomycetemco- toothpaste, or aromatherapy for prevention and treatment of
mitans and P gingivalis clinical isolates were sensitive to related oral infections.
Thymus vulgaris oil with mean minimum inhibitory concentra-
tion 32 mg/mL; however, higher value of Thymus vulgaris oil Acknowledgments
minimum inhibitory concentration (62.5 mg/mL) on these per- The authors would like to thank the Vice Chancellor of Research,
iodontopathic bacteria are reported by other investigators.33 Shiraz University of Medical Sciences, Shiraz, Iran. The editorial
These discrepancies in minimum inhibitory concentration val- assistance of Miss Azadeh Kohanteb is greatly appreciated.
ues reported by different investigators from various regions are
mainly attributed to the fact that Thymus vulgaris oil chemical Author Contributions
composition and active ingredients’ (thymol, carvacrol, P- Both authors have equally contributed to the research and preparation
cymene, etc) concentrations are greatly determined by the plant of this article.
genotype and influence of environmental factors including
geographical conditions, nature of soil, temperature, season Declaration of Conflicting Interests
of collection and harvesting plant, and more important, the oil The authors declared no potential conflicts of interest with respect to
extraction procedure. 4,9,34-37 Much of the antimicrobial the research, authorship, and/or publication of this article.
6 Journal of Evidence-Based Complementary & Alternative Medicine

Funding 14. Kononen E, Paju S, Hyvonen M, et al. Population-based study of

The authors disclosed receipt of the following financial support for the salivary carriage of periodontal pathogens in adults. J Clin Micro-
research, authorship, and/or publication of this article: This project biol. 2007;45:2446-2451.
was financially supported by the Vice Chancellor of Research, Shiraz 15. Neeman R, Keller N, Barzilai A, et al. Prevalence of
University of Medical Sciences (Grant No. 5638). internalization-associated gene prtF1, among persisting group A
Streptococcus strains isolated from asymptomatic carriers.
Ethical Approval Lancet. 1998;352:1974-1977.
16. Gillespie SH. Failure of penicillin in Streptococcus pyogenes
Written consents were obtained from the School of Dentistry Ethics
pharyngeal infection. Lancet. 1998;352:1954-1956.
Committee and patients prior to sample collection.
17. Pichichero ME, Casey JR, Mayes T, et al. Penicillin failure in
Streptoccocal tonsillo pharyngitis: cases and remedies. Pediatr
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