ArticlePDF Available

Antimicrobial effects of mustard oil-containing plants against oral pathogens: an in vitro study

Authors:

Abstract and Figures

Abstract Background: The present study examines the antimicrobial activity of nasturtium herb (Tropaeoli maji herba) and horseradish root (Armoraciae rusticanae radix) against clinically important oral bacterial pathogens involved in periodontitis, gingivitis, pulpitis, implantitis and other infectious diseases. Methods: A total of 15 oral pathogens, including members of the genera Campylobacter, Fusobacterium, Prevotella, Parvimonas, Porphyromonas, Tanerella, Veillonella, and HACEK organisms, were exposed to [1] a combination of herbal nasturtium and horseradish using a standardized gas test and [2] a mixture of synthetic Isothiocyantes (ITCs) using an agardilution test. Headspace gas chromatography mass spectrometry was employed to quantify the amount of allyl-, benzyl-, and 2- phenyl- ethyl-ITC. Results: With exception of Veillonella parvula, all tested species were highly susceptible to herbal nasturtium and horseradish in the gas test with minimal inhibitory concentrations (MICs) between 50/20 mg and 200/80 mg and to synthetic ITCs in the agardilution with MICs between 0.0025 and 0.08 mg ITC/mL, respectively. Minimal bactericidal concentrations extended from 0.005 mg ITC/mL to 0.34 mg ITC/mL. Conclusions: ITCs may be considered an interesting alternative to antibiotics for prevention and treatment of oropharyngeal infections, periodontitis and related diseases. Furthermore, the suitability of ITCs for endocarditis prophylaxis in dental procedures might be worth further investigation.
This content is subject to copyright. Terms and conditions apply.
R E S E A R C H A R T I C L E Open Access
Antimicrobial effects of mustard oil-
containing plants against oral pathogens:
an in vitro study
Vanessa Eichel
1*
, Anne Schüller
2
, Klaus Biehler
2
, Ali Al-Ahmad
3
and Uwe Frank
1,2
Abstract
Background: The present study examines the antimicrobial activity of nasturtium herb (Tropaeoli maji herba) and
horseradish root (Armoraciae rusticanae radix) against clinically important oral bacterial pathogens involved in
periodontitis, gingivitis, pulpitis, implantitis and other infectious diseases.
Methods: A total of 15 oral pathogens, including members of the genera Campylobacter, Fusobacterium, Prevotella,
Parvimonas, Porphyromonas, Tanerella, Veillonella, and HACEK organisms, were exposed to [1] a combination of
herbal nasturtium and horseradish using a standardized gas test and [2] a mixture of synthetic Isothiocyantes (ITCs)
using an agardilution test. Headspace gas chromatography mass spectrometry was employed to quantify the
amount of allyl-, benzyl-, and 2- phenyl- ethyl-ITC.
Results: With exception of Veillonella parvula, all tested species were highly susceptible to herbal nasturtium and
horseradish in the gas test with minimal inhibitory concentrations (MICs) between 50/20 mg and 200/80 mg and to
synthetic ITCs in the agardilution with MICs between 0.0025 and 0.08 mg ITC/mL, respectively. Minimal bactericidal
concentrations extended from 0.005 mg ITC/mL to 0.34 mg ITC/mL.
Conclusions: ITCs may be considered an interesting alternative to antibiotics for prevention and treatment of
oropharyngeal infections, periodontitis and related diseases. Furthermore, the suitability of ITCs for endocarditis
prophylaxis in dental procedures might be worth further investigation.
Keywords: Periodontitis, Isothiocyanates, Mustard oils, Endocarditis prophylaxis, Horseradish, Nasturtium
Background
With increasing spread of antibiotic-resistant pathogens,
and better understanding of the effects of antibiotics on
the microbiota, alternatives to antibiotics must be con-
sidered for therapy and prevention.
The discovery in 1928 of penicillin by Alexander Flem-
ing heralded the golden era of antibiotics, which, lasting
until the late 1960s, saw the development of different
novel antibiotic classes [1,2]. Many bacterial pathogens,
however, developed resistance to most of these antibi-
otics, and the paucity in the development of new antibi-
otics from the 1970s to the present day threatens a
return to the preantibiotic era [14]. Additionally, resist-
ance to disinfectants such as chlorhexidine digluconate
may correlate with antibiotic resistance [57]. Due to
the correlation observed between resistance against dis-
infectants and antibiotics, widespread use of disinfec-
tants should be reassessed [6]. Considering the
aforementioned points, there is substantial need for al-
ternative treatment methods to control oral infections.
Nasturtium (Tropaeolum majus L., TR) herb and
horseradish (Armoracia rusticana P.Gaertn., B.Mey. &
© The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License,
which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give
appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if
changes were made. The images or other third party material in this article are included in the article's Creative Commons
licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons
licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain
permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the
data made available in this article, unless otherwise stated in a credit line to the data.
* Correspondence: vanessa.eichel@med.uni-heidelberg.de
1
Center for Infectious Diseases, Heidelberg University Hospital, Im
Neuenheimer Feld 324, 69120 Heidelberg, Germany
Full list of author information is available at the end of the article
BMC Complementary
Medicine and Therapie
s
Eichel et al. BMC Complementary Medicine and Therapies (2020) 20:156
https://doi.org/10.1186/s12906-020-02953-0
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Scherb., AR) root release high amounts of isothiocya-
nates (ITCs) when glucosinolates - the inactive prodrugs
of ITCs found naturally in Brassica plants - are hydro-
lysed by myrosinases, which are also present in Brassica
plants [8,9]. Several in-vitro studies have demonstrated
that herbal ITCs display antimicrobial effects against a
variety of bacteria including multidrug-resistant (MDR)
bacteria, such as methicillin-resistant Staphylococcus
aureus, vancomycin-resistant Enterococci,MDR Escheri-
chia coli, penicillin-resistant Streptococcus pneumoniae,
biofilm-producing Pseudomonas aeruginosa and also
against viruses [1014]. Clinical studies have demon-
strated the non-inferiority of TR/AR compared to stand-
ard antibiotics in upper respiratory tract infections such
as acute sinusitis and bronchitis treatment [15,16] and
their efficacy in prophylaxis of both respiratory and urin-
ary tract infections [17,18].
The objective of this in-vitro study was to assess the
antimicrobial effects of TR/AR on clinically important
oral pathogens. A total of 15 bacterial strains, (Campylo-
bacter concisus, Campylobacter rectus, Fusobacterium
naviforme, Fusobacterium nucleatum, Parvimonas micra,
Prevotella baroniae, Prevotella intermedia, Porphyromo-
nas gingivalis, Tannerella forsythia, Veillonella parvula),
including 5 HACEK organisms (Haemophilus aphrophi-
lus, Aggregatibacter actinomycetemcomitans, Cardiobac-
terium hominis,Eikenella corrodens,Kingella kingae),
involved in periodontitis and other diseases and one ref-
erence strain (Clostridium perfringens) were assessed.
Table 1gives an overview of the diseases these strains
may cause.
Methods
Headspace gas chromatography mass spectrometry
To identify the amount of allylITC, benzylITC, and 2-
phenyl-ethylITC in TR and AR, headspace gas chroma-
tography mass spectrometry (GC-MS) was employed.
For calibration 0.1, 0.5, 1, 2.5, or 5 μL of a ITC stock so-
lution (ITC:Methanol = 1:100) was added to 500 μLH
2
0
in a 10 mL glass vial. After 30 min shaking at 60 °C
500 μL gas were analyzed using a GC-MS-QP2010S (Shi-
madzu) equipped with a 30 m × 0.32 mm HP-VOC capil-
lary column. The flow rate of the carrier gas helium was
1 mL/min. The column temperature was programmed
from 60 °C to 220 °C at a rate of 10 °C/min. The temper-
atures of the injector and detector were set to 200 °C
and 280 °C, respectively. The experiments were carried
out with electron impact ionization (EI) mode at elec-
tron energy of 70 eV. The degradation products were
identified by matching the recorded mass spectra with
the NIST 107 mass spectrum library of the GC-MS data
system. Mass-to-charge ratios for benzyl-ITC were 149
m/z and 91 m/z, for allylITC 99 m/z and 41 m/z, and
for 2-phenyl-ethylITC 163 m/z and 91 m/z,
respectively. For testing TR and AR, 1 mg of the dried
plant was activated with 500 μLH
2
0 and ITCs amounts
were measured in the same way as the calibration stock.
Cultivation of bacterial strains
The bacterial strains were chosen from the collection of
the microbiological institute of the university hospital of
Freiburg, Germany. They were cultivated under different
conditions corresponding to their special needs. Yeast-
cysteine-blood (YCB) agar plates containing 5% sheep
blood were prepared. The anaerobes Aggregatibacter
actinomycetemcomitans, Campylobacter concisus, Cam-
pylobacter rectus, Clostridium perfringens, Parvimonas
micra, Prevotella baroniae, Prevotella intermedia, Por-
phyromonas gingivalis, Tannerella forsythia, and Veillo-
nella parvula were cultured on the agar plates in
Anaerocult pots (Becton Dickinson and Merck) in which
the anaerobic conditions were monitored by Dry Anaer-
obic Indicator Strips (Becton Dickinson). The micro-
aerophilic strains, Fusobacterium naviforme and
nucleatum, Haemophilus aphrophilus, Kingella kingae,
Eikenella corrodens and Cardiobacterium hominis grew
at 5% CO
2.
The plates were incubated at 36.5 °C, and
32.5 °C for Prevotella intermedia and Prevotella baronie.
Preparation of bacterial stock solution
To achieve quantitative results, a defined amount of bac-
teria should be used for sensitivity tests. The bacterial
stock solutions were prepared by harvesting bacterial
colonies from the plates with sterile cotton swabs and
suspending them in 1 mL PBS (Dulbecco Biochrom).
The turbidity of the suspensions was adjusted to McFar-
land standard 0.5, which corresponds to a concentration
of approximately 10
8
cells/mL. The solution was diluted
with PBS to a final concentration of 10
4
cells/mL.
Table 1 Diseases caused by the bacterial strains tested
(adapted from (Lamont and Jenkinson 2010))
Disease Involved species
Gingivitis Fusobacterium spp., Prevotella spp., Campylobacter spp.
Periodontitis Aggregatibacter actinomycetemcomitans, Campylobacter
spp., Eikenella corrodens, Fusobacterium spp.,
Porphyromonas gingivalis, Prevotella spp., Tannerella
forsythia, Veillonella parvula
Implantitis Porphyromonas gingivalis, Prevotella spp.
Pulpitis Fusobacterium spp., Parvimonas micra, Porphyromonas
ginigvalis
Halitosis Fusobacterium spp., Porphyromonas gingivalis, Prevotella
spp.
Pharyngitis Haemophilus aphrophilus
Tonsillitis Haemophilus aphrophilus
Meningitis Veillonella parvula
Endocarditis Haemophilus aphrophilus, Aggregatibacter actinomycetemcomitans,
Cardiobacterium hominis, Eikenella corrodens, Kingella kingae
Eichel et al. BMC Complementary Medicine and Therapies (2020) 20:156 Page 2 of 7
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Phytotherapeutic drug susceptibility testing with gas test
The antimicrobial effects of the herbal drugs were
assessed using a modified gas test (Fig. 1). Cover plates
were filled with the native substances TR herb powder
(18,834, supplier Martin Bauer) and AR root powder
(17,604, supplier Peter) at a ratio of 2.5:1 (REPHA
GmbH, Langenhagen, Germany). Amounts of TR/AR
ranged from 12.5/5 mg, which corresponds to 1/16 of
the commercially available tablet Angocin®and to 400/
160 mg, which corresponds to 2 tablets. A negative con-
trol with an empty cover plate was added to each series.
The bacterial stock solutions were spread on YCB agar
plates and the drugs were activated by stirring in 2 mL
PBS. The plates were assembled, closed with parafilm,
and incubated at 32.5 °C and checked for bacterial
growth after 48 and 72 h, respectively, by counting col-
ony forming units (CFU). Minimal inhibitory concentra-
tions (MIC) were defined as the lowest concentration of
TR/AR to prevent visible bacterial growth. Every strain
was tested at least twice with this assay. MIC values are
mean values.
ITC susceptibility testing with agardilution
To verify the effects observed in the gas test, synthetic
ITCs were used to perform agar dilution tests. To reflect
the proportions of active agents in Angocin®, a mixture
of 38% allyl-ITC (Merck), 50% benzyl-ITC (Sigma-Al-
drich), and 12% 2-phenyl-ethyl-ITC (Fluka) was pre-
pared. 1% (v/v) polysorbate 80 (Merck Schuchardt)
served as a solvent to dilute the lipophilic mixture. The
ITC/polysorbate mixture was diluted nine times 1:1 to
prepare the desired concentrations. Series of YCB agar
plates with ITC concentrations from 0.0025 mg/mL to
0.34 mg/mL were poured by adding 2 mL ITC/polysor-
bate mixture to 18 mL liquid YCB agar. The bacterial
stock solution with a concentration of 10
4
cells/mL was
inoculated using a multipoint-inoculator (Mast). As a
negative control, 2 mL polysorbate without ITC was
added to the YCB agar. The inoculated agar plates were
incubated at 32.5 °C up to 5 days, depending on the par-
ticular bacterial growth rate. Anaerobes were cultivated
in Anaerocult pots, microaerophilic bacteria at 5% CO
2
.
The plates were checked for bacterial growth after 48
and 72 h, respectively. Each strain was tested at least
twice with this assay. The minimal bactericidal concen-
tration (MBC) is the lowest ITC concentration required
to kill the bacterium. For determination of the MBC
values, inoculated areas which showed no visible bacter-
ial growth after 48 h incubation were transferred with a
sterile swab to an ITC-free YBC agar plate, and checked
for bacterial growth after 48 and 72 h, respectively. Each
strain was tested at least twice with this assay. MIC and
MBC values are mean values.
Results
Horseradish and Nasturtium powder release high
amounts of Isothiocyanates
With headspace GC-MS we measured considerable
amounts of ITCs in the gases, when Tropaeolum majus
and Armoraciae rusticanae powder was activated with
water (Fig. 2). While TR mainly contained benzylITC
(0.046 ± 0.001 μL/mg), AR released huge amounts of
allylITC (0.033 ± 0.001 μL/mg), and 2-phenyl-ethyl
ITC (0.0023 ± 0.0005 μL/mg).
Phytotherapeutic drugs inhibit bacterial growth
All species were highly susceptible to herbal TR/AR in
the gas test and to synthetic ITC in the agar dilution
test, except for Veillonella parvula. MIC values were de-
termined between 50/20 mg and 200/80 mg TR/AR, and
0.0025 and 0.08 mg ITC/mL, as shown in Fig. 3. The
highest susceptibility was shown for Tannerella forsythia
in both, the gas test and the agardilution. However, in
the gas test growth of Porphyromonas gingivalis, Fuso-
bacterium nucleatum, and Prevotella baroniae was also
inhibited at 50/20 mg TR/AR. The agardilution experi-
ments revealed that after Tannerella Porphyromonas
ginigvalis, Cardiobacterium hominis, and Kingella klin-
gae were next susceptible to ITCs. MBCs extended from
0.005 mg ITC/mL for Tannerella forsythia to 0.34 mg
ITC/mL for Fusobacterium naviforme, Fusobacterium
nucleatum, and Eikenella corrodens. Growth of Veillo-
nella parvula was not influenced by TR/AR or synthetic
ITCs at the concentrations tested. Negative control
plates without antibiotic agents showed normal bacterial
growth.
Fig. 1 Opened apparatus for gas test experiments
Eichel et al. BMC Complementary Medicine and Therapies (2020) 20:156 Page 3 of 7
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Discussion
High antimicrobial effects
The antimicrobial effects of Tropaeolum majus L. (TR)
and Armoracia rusticana P.Gaertn., B.Mey. & Scherb
(AR) against oral pathogenic bacteria have not been
studied sufficiently, so far. Hence, the aim of our study
was to determine the susceptibilities of clinically import-
ant oral pathogens and to show that TR and AR are
feasible for the usage in antimicrobial therapy in
patients.
In addition to the frequently used standard MIC-
Methodsamodifiedgastestsetupwasusedto
evaluate the antimicrobial effects of the dried plant
powder [19,20].
Prior to testing the antimicrobial activity, the active
substances of TR and AR were analyzed in detail
using headspace gas chromatography mass spectrom-
etry (GC-MS). We found chemically different ITCs in
the two plants, which favors the use of a combination
of ITC-containing plants. For our susceptibility tests,
we therefore used a mixture of TR and AR at a pro-
portion of 2.5:1 and a combination of synthetically
produced ITCs with matches the proportions of ITCs
in the plants.
With the exception of Veillonella parvula, all tested
species were highly susceptible to herbal TR/AR in the
Fig. 2 GC-MS defined ITC amounts in Nasturtium and Horseradish;
AITC: allylITC; BITC: benzylITC, 2PEITC: 2- phenyl- ethylITC; n=3
Fig. 3 blue: MIC values of TR/AR in gas tests (right scale); orange, red: MIC and MBC values of synthetic isothiocyanates in agardilution tests (left
scale); >: maximum test concentration reached; n=2
Eichel et al. BMC Complementary Medicine and Therapies (2020) 20:156 Page 4 of 7
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
gas test and synthetic ITCs in the agar dilution, with
MICs ranging between 50/20 mg and 200/80 mg TR/AT,
and 0.01 and 0.08 mg ITC/mL, respectively. Tannerella
forsythia, Porphyromonas gingivalis, Fusobacterium
nucleatum and Prevotella baroniae were found to be the
most sensitive of the tested species, as 50/20 mg TR/AR,
which equates to only 1/4 tablet of the commercially
available drug (Angocin®), was enough to stop growth.
MBC values were about 4 to 10 times higher than MIC
values. Although the order of herbal MIC values does
not exactly correlate with the sequence of synthetic ITC
MIC and MBC values, all determined concentrations
could easily be reached in the oral cavity by topical ap-
plication as mouthwash, gel, chip, or, in combination
with fluoride, as toothpaste.
Our GC-MS experiments demonstrated, that a mixture
of herbal TR/AR powder can release a spectrum of ITCs
in high amounts. Previous studies tested TR alone for its
bactericidal effect on certain oral pathogens. However, the
ITC solution was sucked in a paper disk and placed on
the agar. The MBC values of the ITCs extracted from TR
and the synthetic allyl- ITC were higher than in our ex-
periments [21]. This could mean that the combination of
TR and AR is more effective than TR alone.
Furthermore, Salvadora persica, sticks of which have
been used as natural toothbrushes for centuries, were
found to contain high amounts of benzyl-ITC and show
considerable antimicrobial effects on Aggregatibacter
actinomycetemcomitans and Porphyromonas gingivalis
[22]. This is consistent with the results presented in this
study for ITCs.
Why phytotherapeutic drugs?
Although TR and AR are cultivated and have been
used for hundreds of years, relevant bacterial resis-
tances to ITCs have not as yet been reported. The
safety of systemic TR/AR administration up to 1200/
480 mg daily was demonstrated in a clinical trial [17].
Adverse side effects were significantly lower in a TR/
ARgroupthananantibioticgroup[16]. Negative ef-
fects on the gut microbiota were not observed. More-
over, the treatment costs with TR/AR are
substantially lower than with antibiotic prescriptions.
Additionally, chlorhexidine, which has been consid-
ered the gold standard in dental plaque control [23],
is also cytotoxic, as reported for human gingival fi-
broblasts, osteosarcoma cells and osteoblasts [24,25].
Moreover, human saliva can to some extent inactivate
the antibacterial effects of chlorhexidine against some
oral bacteria, inducing selective processes in the bac-
terial populations of human saliva [26]. Furthermore,
a correlation of resistance towards chlorhexidine and
different medically relevant antibiotics cannot be ex-
cluded due to the similar mechanisms of resistance
which include multidrug efflux pumps and cell mem-
brane changes as reported in an own review of the
literature [27]. Another frequently used oral health
product is Listerine® [28]. Although there is accumu-
lating evidence that Listerine® is effective in improving
oral health, the absence of systematic toxicological
studies means that an accurate safety assessment can-
notbemade[29]. Hence, new natural antibacterial
compoundssuchasITCsfromplantscouldbeprom-
ising components for dental oral care. However, the
direct comparison of ITCs effects on oral pathogens
with standard antibiotics or chlorhexidine is still
pending, which must be acknowledged as a limitation
of our study approach.
Clinical benefit
Out of the tested species, Aggregatibacter actinomyce-
temcomitans, Campylobacter rectus, Eikenella corrodens,
Fusobacterium nucleatum, Porphyromonas gingivalis,
Prevotella intermedia, Tanerella forsythia, and Veillo-
nella parvula are highly associated with periodontitis
[30,31]. With the exception of Veillonella parvula, all
these pathogens were found to be highly susceptible to
ITCs. The topical use of herbal TR/AR, e.g. as antiseptic
mouthwash, gel or chip, should be considered, but also
systemic administration, since the compliance to phy-
totherapy is usually good, and spread of antibiotic resist-
ance could be avoided. Activity exhibited by ITCs against
biofilms was demonstrated by the example of Pseudo-
monas aeruginosa [12]. The effects against the diverse
array of oral bacteria tested in the present study suggest
an anti-biofilm effect of ITCs. Such potential should be
examined in future studies to clarify inhibition of forma-
tion or degradation of already formed oral biofilm.
Endocarditis prophylaxis for dental procedures should
predominantly cover Staphylococci,Streptococci, Entero-
cocci, and Candida spp.,but also incidental pathogens
such as HACEK organisms [32]. Our in vitro-study dem-
onstrated that HACEK organisms are highly susceptible
to TR/AR. These results support and expand our previ-
ous findings of the antibacterial effect of mustard oil-
containing plants against the predominant endocarditis
relevant oral bacteria [10].
Conclusions
This study showed that different components of mustard
oil-containing plants have a high antimicrobial activity
against various oral bacteria. The presented results sug-
gest a high potential activity against oral biofilm forma-
tion which should be tested in vivo in future clinical
studies to evaluate their beneficial protective effects to
prevent oral diseases such as caries, periodontitis and
periimplantitis.
Eichel et al. BMC Complementary Medicine and Therapies (2020) 20:156 Page 5 of 7
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Supplementary information
Supplementary information accompanies this paper at https://doi.org/10.
1186/s12906-020-02953-0.
Additional file 1: Table S1. Exposed species and its corresponding MIC
values of nasturtium herb and horseradish root in gas tests, as well as
MIC and MBC values of synthetic isothiocyanates in agardilution tests; n.d:
not defined.
Abbreviations
AR: Armoracia rusticana P.Gaertn., B.Mey. & Scherb; CFU: Colony forming
units; ITC: Isothiocyanate; MBC: Minimal bactericidal concentration;
MDR: Multidrug-resistant; MIC: Minimal inhibitory concentration;
TR: Tropaeolum majus L.; YCB: Yeast-cysteine-blood
Acknowledgements
We thank Ms. Lawrie-Blum for proofreading.
Authorscontributions
VE contributed to conception, conducted the gas chromatic experiments,
interpreted and analyzed the data, and has drafted the manuscript. AS
contributed to conception, performed the phytotherapeutic drug testing,
interpreted and analyzed the data. KB contributed to conception, supervised
the phytotherapeutic drug testing, interpreted and analyzed the data, and
contributed to the manuscript. AAA contributed to interpretation of the data
and substantively revised the manuscript. UF initiated the project and
received the financial support, contributed to conception and design,
supervised all experiments and critically revised the manuscript. All authors
read and approved the final manuscript.
Funding
This work was supported by Repha GmbH, Langenhagen, Germany [Grant
number D: 100 60 723, C: 50 30 25]. Repha GmbH was neither involved in
conducting the experiments, interpreting the results nor in the writing of
this manuscript.
We acknowledge financial support by Deutsche Forschungsgemeinschaft
within the funding programme Open Access Publishing, by the Baden-
Württemberg Ministry of Science, Research and the Arts and by Ruprecht-
Karls-Universität Heidelberg.
Availability of data and materials
The datasets used and/or analysed during the current study are available
from the corresponding author on reasonable request.
Ethics approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Author details
1
Center for Infectious Diseases, Heidelberg University Hospital, Im
Neuenheimer Feld 324, 69120 Heidelberg, Germany.
2
Institute for Infection
Prevention and Hospital Epidemiology, University of Freiburg, Breisacher
Straße 115 B, 79106 Freiburg, Germany.
3
Department of Operative Dentistry
and Periodontology, Freiburg University Hospital, Hugstetterstrasse 55, 79106
Freiburg, Germany.
Received: 14 February 2020 Accepted: 14 May 2020
References
1. Aminov RI. A brief history of the antibiotic era: lessons learned and
challenges for the future. Front Microbiol. 2010;1:134.
2. Renwick MJ, Simpkin V, Mossialos E. European Observatory Health Policy
Series. Targeting innovation in antibiotic drug discovery and development:
The need for a One Health - One Europe - One World Framework.
Copenhagen (Denmark): European Observatory on Health Systems and
Policies World Health Organization 2016; 2016.
3. Laxminarayan R, Matsoso P, Pant S, Brower C, Rottingen JA, Klugman K,
et al. Access to effective antimicrobials: a worldwide challenge. Lancet
(London, England). 2016;387(10014):16875.
4. Lewis K. Antibiotics: recover the lost art of drug discovery. Nature. 2012;
485(7399):43940.
5. Meyer B, Cookson B. Does microbial resistance or adaptation to biocides
create a hazard in infection prevention and control? J Hospital Infect. 2010;
76(3):2005.
6. Kampf G. Acquired resistance to chlorhexidine - is it time to establish an
antiseptic stewardshipinitiative? J Hospital Infect. 2016;94(3):21327.
7. Horner C, Mawer D, Wilcox M. Reduced susceptibility to chlorhexidine in
staphylococci: is it increasing and does it matter? J Antimicrob Chemother.
2012;67(11):254759.
8. Dufour V, Stahl M, Baysse C. The antibacterial properties of isothiocyanates.
Microbiology (Reading, England). 2015;161(Pt 2):22943.
9. Benyelles B, Allali H, Fekih N, Touaibia M, Muselli A, Nassim D, et al.
Chemical Composition of the Volatile Components of Tropaeolum majus L.
(Garden Nasturtium) from North Western Algeria. Phyto Chem Bio Sub J.
2015;9.
10. Conrad A, Biehler D, Nobis T, Richter H, Engels I, Biehler K, et al. Broad
spectrum antibacterial activity of a mixture of isothiocyanates from
nasturtium (Tropaeoli majoris herba) and horseradish (Armoraciae rusticanae
radix). Drug Res. 2013;63(2):658.
11. Mutters NT, Mampel A, Kropidlowski R, Biehler K, Gunther F, Balu I, et al.
Treating urinary tract infections due to MDR E. coli with Isothiocyanates - a
phytotherapeutic alternative to antibiotics? Fitoterapia. 2018;129:23740.
12. Kaiser SJ, Mutters NT, Blessing B, Gunther F. Natural isothiocyanates express
antimicrobial activity against developing and mature biofilms of
Pseudomonas aeruginosa. Fitoterapia. 2017;119:5763.
13. Romeo L, Iori R, Rollin P, Bramanti P, Mazzon E. Isothiocyanates: An
Overview of Their Antimicrobial Activity against Human Infections.
Molecules (Basel, Switzerland). 2018;23(3).
14. Aires A, Mota VR, Saavedra MJ, Rosa EAS, Bennett RN. The antimicrobial
effects of glucosinolates and their respective enzymatic hydrolysis products
on bacteria isolated from the human intestinal tract. J Appl Microbiol. 2009;
106(6):208695.
15. Goos KH, Albrecht U, Schneider B. Efficacy and safety profile of a herbal
drug containing nasturtium herb and horseradish root in acute sinusitis,
acute bronchitis and acute urinary tract infection in comparison with other
treatments in the daily practice/results of a prospective cohort study.
Arzneimittelforschung. 2006;56(3):24957.
16. Goos KH, Albrecht U, Schneider B. On-going investigations on efficacy and
safety profile of a herbal drug containing nasturtium herb and horseradish
root in acute sinusitis, acute bronchitis and acute urinary tract infection in
children in comparison with other antibiotic treatments.
Arzneimittelforschung. 2007;57(4):23846.
17. Fintelmann V, Albrecht U, Schmitz G, Schnitker J. Efficacy and safety of a
combination herbal medicinal product containing Tropaeoli majoris herba
and Armoraciae rusticanae radix for the prophylactic treatment of patients
with respiratory tract diseases: a randomised, prospective, double-blind,
placebo-controlled phase III trial. Curr Med Res Opin. 2012;28(11):1799807.
18. Albrecht U, Goos KH, Schneider B. A randomised, double-blind, placebo-
controlled trial of a herbal medicinal product containing Tropaeoli majoris
herba (Nasturtium) and Armoraciae rusticanae radix (horseradish) for the
prophylactic treatment of patients with chronically recurrent lower urinary
tract infections. Curr Med Res Opin. 2007;23(10):241522.
19. CLSI. Performance Standards for Antimicrobial Disk Susceptibility Tests,
Approved Standard, CLSI document M02-A11. 7th ed. Pennsylvania 19087,
USA: Clinical and Laboratory Standards Institute, 950 West Valley Road, Suite
2500, Wayne; 2012.
20. Winter AG, Hornbostel M. Untersuchungen über Antibiotika aus höheren
Pflanzen: IX. Mitteilung: Gasförmige Hemmstoffe aus Cochlearia armoracia
(Meerrettich) und ihr Verhalten im menschlichen Körper bei Aufnahme per
os. Naturwiss. 1953;40:48990.
21. Park H-W, Choi K-D, Shin I-S. Antimicrobial activity of Isothiocyanates
extracted from horseradish root against Oral microorganisms. Biocontrol
Science. 2013;18(3):1638.
22. Sofrata A, Santangelo EM, Azeem M, Borg-Karlson A-K, Gustafsson A, Pütsep
K. Benzyl Isothiocyanate, a major component from the roots of Salvadora
Eichel et al. BMC Complementary Medicine and Therapies (2020) 20:156 Page 6 of 7
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Persica is highly active against gram-negative Bacteria. PLoS One. 2011;6(8):
e23045.
23. Quirynen M, Avontroodt P, Peeters W, Pauwels M, Coucke W, van
Steenberghe D. Effect of different chlorhexidine formulations in
mouthrinses on de novo plaque formation. J Clin Periodontol. 2001;28(12):
112736.
24. John G, Becker J, Schwarz F. Effects of Taurolidine and Chlorhexidine on
SaOS-2 cells and human gingival fibroblasts grown on implant surfaces. The
international journal of Oral &amp. Maxillofacial Implants. 2014;29(3):72834.
25. Proksch S, Strobel SL, Vach K, Abouassi T, Tomakidi P, Ratka-Kruger P, et al.
Melatonin as a candidate therapeutic drug for protecting bone cells from
chlorhexidine-induced damage. J Periodontol. 2014;85(12):e37989.
26. Abouassi T, Hannig C, Mahncke K, Karygianni L, Wolkewitz M, Hellwig E,
et al. Does human saliva decrease the antimicrobial activity of chlorhexidine
against oral bacteria? BMC Res Notes. 2014;7:711.
27. Cieplik F, Jakubovics NS, Buchalla W, Maisch T, Hellwig E, Al-Ahmad A.
Resistance toward Chlorhexidine in Oral Bacteria - is there cause for
concern? Front Microbiol. 2019;10:587.
28. Vlachojannis C, Chrubasik-Hausmann S, Hellwig E, Al-Ahmad A. A
preliminary investigation on the antimicrobial activity of Listerine(R), its
components, and of mixtures thereof. Phytotherapy Res PTR. 2015;29(10):
15904.
29. Vlachojannis C, Al-Ahmad A, Hellwig E, Chrubasik S. Listerine(R) products: an
update on the efficacy and safety. Phytotherapy Res PTR. 2016;30(3):36773.
30. Könönen E, Müller H-P. Microbiology of aggressive periodontitis.
Periodontol. 2014;65(1):4678.
31. Picolos DK, Lerche-Sehm J, Abron A, Fine JB, Papapanou PN. Infection
patterns in chronic and aggressive periodontitis. J Clin Periodontol. 2005;
32(10):105561.
32. Cahill TJ, Prendergast BD. Infective endocarditis. Lancet (London, England).
2016;387(10021):88293.
PublishersNote
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
Eichel et al. BMC Complementary Medicine and Therapies (2020) 20:156 Page 7 of 7
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
1.
2.
3.
4.
5.
6.
Terms and Conditions
Springer Nature journal content, brought to you courtesy of Springer Nature Customer Service Center GmbH (“Springer Nature”).
Springer Nature supports a reasonable amount of sharing of research papers by authors, subscribers and authorised users (“Users”), for small-
scale personal, non-commercial use provided that all copyright, trade and service marks and other proprietary notices are maintained. By
accessing, sharing, receiving or otherwise using the Springer Nature journal content you agree to these terms of use (“Terms”). For these
purposes, Springer Nature considers academic use (by researchers and students) to be non-commercial.
These Terms are supplementary and will apply in addition to any applicable website terms and conditions, a relevant site licence or a personal
subscription. These Terms will prevail over any conflict or ambiguity with regards to the relevant terms, a site licence or a personal subscription
(to the extent of the conflict or ambiguity only). For Creative Commons-licensed articles, the terms of the Creative Commons license used will
apply.
We collect and use personal data to provide access to the Springer Nature journal content. We may also use these personal data internally within
ResearchGate and Springer Nature and as agreed share it, in an anonymised way, for purposes of tracking, analysis and reporting. We will not
otherwise disclose your personal data outside the ResearchGate or the Springer Nature group of companies unless we have your permission as
detailed in the Privacy Policy.
While Users may use the Springer Nature journal content for small scale, personal non-commercial use, it is important to note that Users may
not:
use such content for the purpose of providing other users with access on a regular or large scale basis or as a means to circumvent access
control;
use such content where to do so would be considered a criminal or statutory offence in any jurisdiction, or gives rise to civil liability, or is
otherwise unlawful;
falsely or misleadingly imply or suggest endorsement, approval , sponsorship, or association unless explicitly agreed to by Springer Nature in
writing;
use bots or other automated methods to access the content or redirect messages
override any security feature or exclusionary protocol; or
share the content in order to create substitute for Springer Nature products or services or a systematic database of Springer Nature journal
content.
In line with the restriction against commercial use, Springer Nature does not permit the creation of a product or service that creates revenue,
royalties, rent or income from our content or its inclusion as part of a paid for service or for other commercial gain. Springer Nature journal
content cannot be used for inter-library loans and librarians may not upload Springer Nature journal content on a large scale into their, or any
other, institutional repository.
These terms of use are reviewed regularly and may be amended at any time. Springer Nature is not obligated to publish any information or
content on this website and may remove it or features or functionality at our sole discretion, at any time with or without notice. Springer Nature
may revoke this licence to you at any time and remove access to any copies of the Springer Nature journal content which have been saved.
To the fullest extent permitted by law, Springer Nature makes no warranties, representations or guarantees to Users, either express or implied
with respect to the Springer nature journal content and all parties disclaim and waive any implied warranties or warranties imposed by law,
including merchantability or fitness for any particular purpose.
Please note that these rights do not automatically extend to content, data or other material published by Springer Nature that may be licensed
from third parties.
If you would like to use or distribute our Springer Nature journal content to a wider audience or on a regular basis or in any other manner not
expressly permitted by these Terms, please contact Springer Nature at
onlineservice@springernature.com
Chapter
Glycosides represent a large group of secondary metabolic products derived from plants, demonstrating several known functions, including growth regulation, allelopathy (inhibition of other plant growth), and defense mechanisms against damage induced by herbivores and pathogens. They are composed of two bound portions, a sugar moiety, named glycone, and a second portion known as the aglycone or genin. The anthraquinone, cardiac, coumarin, cyanogenic, flavonoid, glucosinolates, phenol, and saponin glycosides are discussed in the text.
Article
Full-text available
The threat of antibiotic resistance has attracted strong interest during the last two decades, thus stimulating stewardship programs and research on alternative antimicrobial therapies. Conversely, much less attention has been given to the directly related problem of resistance toward antiseptics and biocides. While bacterial resistances toward triclosan or quaternary ammonium compounds have been considered in this context, the bis-biguanide chlorhexidine (CHX) has been put into focus only very recently when its use was associated with emergence of stable resistance to the last-resort antibiotic colistin. The antimicrobial effect of CHX is based on damaging the bacterial cytoplasmic membrane and subsequent leakage of cytoplasmic material. Consequently, mechanisms conferring resistance toward CHX include multidrug efflux pumps and cell membrane changes. For instance, in staphylococci it has been shown that plasmid-borne qac (“quaternary ammonium compound”) genes encode Qac efflux proteins that recognize cationic antiseptics as substrates. In Pseudomonas stutzeri, changes in the outer membrane protein and lipopolysaccharide profiles have been implicated in CHX resistance. However, little is known about the risk of resistance toward CHX in oral bacteria and potential mechanisms conferring this resistance or even cross-resistances toward antibiotics. Interestingly, there is also little awareness about the risk of CHX resistance in the dental community even though CHX has been widely used in dental practice as the gold-standard antiseptic for more than 40 years and is also included in a wide range of oral care consumer products. This review provides an overview of general resistance mechanisms toward CHX and the evidence for CHX resistance in oral bacteria. Furthermore, this work aims to raise awareness among the dental community about the risk of resistance toward CHX and accompanying cross-resistance to antibiotics. We propose new research directions related to the effects of CHX on bacteria in oral biofilms.
Article
Full-text available
Background: Multidrug-resistant (MDR) bacteria are increasingly causing urinary tract infections (UTI), which has been linked to frequent use of antibiotics. Alternative treatment regimens are urgently needed and natural isothiocyanates (ITC) may represent one. ITCs are natural plant products found in nasturtium (Tropaeoli majoris herba) and horseradish (Armoraciae rusticanae radix). Purpose: The objectives were to (1) assess the antimicrobial effects of nature-identical ITCs for UTI treatment caused by uropathogenic E. coli (UPEC), (2) to evaluate a potential influence of antimicrobial resistance on ITC susceptibility, and (3) to test whether ITCs affect UPEC penetration into human uroepithelial cells. Methods: We tested 217 clinical UPEC isolates, 54.5% of which were classified as MDR, for susceptibility against ITCs. ITC susceptibility testing was performed by broth dilution using a mixture of three synthetic ITCs. Internalization was tested using human T-24 bladder carcinoma cells in an internalization assay co-incubated with UPEC (n = 5) and ITCs. Results: The mean minimal inhibitory concentration (MIC) 90 was 0.17 mg/ml, showing very high susceptibility against ITCs. Interestingly, MDR E. coli were significantly less susceptible than non-MDR strains (p = .01). Internalization of UPEC was decreased by 31.9% in the mean when treated with ITCs. Overall, ITCs exerted a strong antimicrobial activity against clinical UPEC isolates and reduced internalization into uroepithelial cells. Conclusion: ITCs might present a promising treatment alternative for UTIs, expressing both high antimicrobial activity as well as blocking the pathogenic process of human cell penetration by UPEC. Clinical studies, however, are needed to confirm activity of ITCs in UTIs in vivo.
Article
Full-text available
The use of plant-derived products as antimicrobial agents has been investigated in depth. Isothiocyanates (ITCs) are bioactive products resulting from enzymatic hydrolysis of glucosinolates (GLs), the most abundant secondary metabolites in the botanical order Brassicales. Although the antimicrobial activity of ITCs against foodborne and plant pathogens has been well documented, little is known about their antimicrobial properties against human pathogens. This review collects studies that focus on this topic. Particular focus will be put on ITCs’ antimicrobial properties and their mechanism of action against human pathogens for which the current therapeutic solutions are deficient and therefore of prime importance for public health. Our purpose was the evaluation of the potential use of ITCs to replace or support the common antibiotics. Even though ITCs appear to be effective against the most important human pathogens, including bacteria with resistant phenotypes, the majority of the studies did not show comparable results and thus it is very difficult to compare the antimicrobial activity of the different ITCs. For this reason, a standard method should be used and further studies are needed.
Article
Full-text available
Background: The antimicrobial properties of natural isothiocyanates (ITCs) found in plants such as nasturtium (Tropaeolum majus) and horseradish (Armoracia rusticana), and the need of new chemotherapeutic options for treatment of infections caused by multidrug-resistant and biofilm-forming Gram-negative bacteria such as Pseudomonas aeruginosa (Pa), led us to evaluate the effects of three major ITCs, allylisothiocyanate (AITC), benzylisothiocyanate (BITC), and phenylethyl-isothiocyanate (PEITC), and a mixture (ITCM) adapted to the ITC composition after release of active components out of natural sources. Material/methods: Out of 105Pa isolates 27 isolates with increased biofilm formation were selected for testing. The effects of ITCs on Pa were evaluated regarding (1) planktonic bacterial proliferation, (2) biofilm formation, (3) metabolic activity in mature biofilms, and (4) synergism of ITCs and antibiotics. Results: (1) Each ITC had anti-Pa activity. Mean minimum inhibitory concentrations (MICs) were (μg/ml, mean±standard deviation): AITC 103±6.9; BITC, 2145±249; PEITC 29,423±1652; and ITCM, 140±5. (2) Treating bacteria with PEITC and ITCM in concentrations below the MIC significantly inhibited biofilm formation. Particularly, ITCM reduced biofilm mass and bacterial proliferation. (3) ITCs significantly inhibited metabolic activity in mature biofilms. (4) Combining ITCs with meropenem synergistically increased antimicrobial efficacy on Pa biofilms. Conclusions: ITCs represent a promising group of natural anti-infective compounds with activity against Pa biofilms.
Book
Full-text available
Antimicrobial resistance is a global crisis that threatens public health and modern medicine. Discovery and development of novel antibiotic products is a critical component to combating antimicrobial resistance. Numerous initiatives operate at international, European Union and national levels to address the scientific, regulatory and economic barriers to antibiotic innovation. This study identifies, reviews and critically assesses these initiatives, and ultimately provides a set of policy recommendations for improving the global and European research and development agenda for antibiotics.
Article
Full-text available
Essential oil from Tropaeolum majus L. aerial parts, a plant native to North Western Algeria, was obtained by hydrodistillation. The oil volatile components were identified by a combination of gas chromatography/flame ionization detection (GC/FID), GC-mass spectrometry (GC-MS) techniques, and NMR spectroscopy. Nine components representing 92.0 % of the essential oil total (GC/FID chromatogram) were identified. The most abundant compounds were benzyl isothiocyanate (82.5 %), benzene acetonitrile (3.9 %) and 2-phenylethyl isovalerate (2.9 %). Higher content in nitrogen- and sulfur-containing compounds accounting to 86.4 % of the volatile fraction composition of T. majus were quantified.
Article
Chlorhexidine digluconate (CHG) is an antimicrobial agent used for different types of applications in hand hygiene, skin antisepsis, oral care and patient washing. Increasing use raises concern on a development of acquired bacterial resistance. Published data from clinical isolates with CHG MICs were reviewed and compared to epidemiological cut-off values to determine resistance. CHG resistance is rarely found in E. coli, Salmonella spp., S. aureus and CNS. In Enterobacter spp., Pseudomonas spp., Proteus spp., Providencia spp. and Enterococcus spp., however, isolates are more often CHG resistant. CHG resistance can be detected in multi-resistant isolates such as XDR K. pneumoniae. Isolates with a higher MIC are often less susceptible to CHG for disinfection. Although cross-resistance to antibiotics remains controversial some studies indicate that the overall exposure to CHG increases the risk for resistance to some antibiotic agents. Resistance to CHG has resulted in numerous outbreaks and healthcare-associated infections. On an average intensive care unit most of the CHG exposure would be explained by hand hygiene agents when liquid soaps or alcohol-based hand rubs contain CHG. Exposure to sublethal CHG concentration can enhance resistance in Acinetobacter spp., K. pneumoniae and Pseudomonas spp., all species well known for emerging antibiotic resistance. In order to reduce additional selection pressure in nosocomial pathogens it seems to make sense to restrict the valuable agent CHG to those indications with a clear patient benefit and to eliminate it from applications without any benefit or with a doubtful benefit. Free download until December 25, 2016, via the publisher: https://authors.elsevier.com/a/1T-WsiVN-neE3
Article
Unlabelled: In the 19th century, the mouthwash Listerine® was formulated from four essential oils. Later, the oils were replaced by their marker substances. To keep them in solution, 24-27% ethanol was added as a vehicle. This is an update of our previous review on the efficacy and safety of Listerine®. Method: PubMed was searched for clinical studies on the therapeutic benefits and safety of Listerine® from the end of 2011 to the end of October 2015. Results: Sixteen studies were found and extracted. Three of the four 6-month studies were of sound confirmatory design. Two of these investigated Listerine® and one Listerine Zero®. The evidence of effectiveness for Listerine®, based on the bulk of three confirmatory studies and numerous exploratory studies carried out so far, is strong, but only moderate for Listerine® Zero and poor for Listerine® Cool Blue. In the three safety studies identified, we found methodological flaws that biased the results. Conclusions: Evidence is accumulating that Listerine® is effective in improving oral health, but the absence of systematic toxicological studies means that an accurate safety assessment cannot be made.
Article
Recent years have seen substantial improvements in life expectancy and access to antimicrobials, especially in low-income and lower-middle-income countries, but increasing pathogen resistance to antimicrobials threatens to roll back this progress. Resistant organisms in health-care and community settings pose a threat to survival rates from serious infections, including neonatal sepsis and health-care-associated infections, and limit the potential health benefits from surgeries, transplants, and cancer treatment. The challenge of simultaneously expanding appropriate access to antimicrobials, while restricting inappropriate access, particularly to expensive, newer generation antimicrobials, is unique in global health and requires new approaches to financing and delivering health care and a one-health perspective on the connections between pathogen transmission in animals and humans. Here, we describe the importance of effective antimicrobials. We assess the disease burden caused by limited access to antimicrobials, attributable to resistance to antimicrobials, and the potential effect of vaccines in restricting the need for antibiotics.
Article
Infective endocarditis occurs worldwide, and is defined by infection of a native or prosthetic heart valve, the endocardial surface, or an indwelling cardiac device. The causes and epidemiology of the disease have evolved in recent decades with a doubling of the average patient age and an increased prevalence in patients with indwelling cardiac devices. The microbiology of the disease has also changed, and staphylococci, most often associated with health-care contact and invasive procedures, have overtaken streptococci as the most common cause of the disease. Although novel diagnostic and therapeutic strategies have emerged, 1 year mortality has not improved and remains at 30%, which is worse than for many cancers. Logistical barriers and an absence of randomised trials hinder clinical management, and longstanding controversies such as use of antibiotic prophylaxis remain unresolved. In this Seminar, we discuss clinical practice, controversies, and strategies needed to target this potentially devastating disease. Copyright © 2015 Elsevier Ltd. All rights reserved.