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Effectiveness of Alternative Antimicrobial Agents for Disinfection of Hard Surfaces

Authors:
  • ministry of health, Quebec
SEPTEMBER 2011
1
Effectiveness of Alternative
Antimicrobial Agents for
Disinfection of Hard Surfaces
7
Daniel Fong, Colette Gaulin, Mê-Linh Lê, Mona Shum
Summary
A review of alternative antimicrobial
agents reveals the need for
standardized methodology for efficacy
testing as well as considerations of
toxicity, safety, cost, ease of use,
availability, storage, and application-
specific testing.
The appropriateness of alternative
antimicrobial agents, such as vinegar,
lemon juice, and baking soda appear to
be limited for commercial disinfection or
sanitization, but some emerging
technologies such as ozonated water
and electrolyzed water have
demonstrated substantial antimicrobial
properties.
Agents such as tea tree oil may
demonstrate notable antimicrobial
efficacy, but toxicity and lack of testing
on hard surfaces limit their applications
for hard surface disinfection. Thyme oil
exhibits low toxicity and has been
shown to be microbicidal, but its use
may be limited due to the need for long
contact time and costs.
Although lacking active microbicidal
activity, microfibre fabrics have unique
properties that significantly increase
their ability to remove organic debris
(e.g., dust, bacteria, spores) and have
the potential to be more efficient and
economical than conventional cotton
fabrics.
Silver has been demonstrated to show
residual antimicrobial properties. Its
effectiveness in making materials/surfaces
resistant to microbial growth has potential
implications for expanding its use in medical
and commercial applications.
Further research is needed to explore
potential uses of alternative agents in
formulating novel disinfectants with
desirable characteristics (e.g., lower toxicity,
economical, environmentally friendly).
Introduction
Many alternative antimicrobial agents claim to
exhibit comparable disinfection qualities to
traditional disinfectants and sanitizers,a
such as
accelerated hydrogen peroxide, quaternary
ammonium compounds (QUATs), and chlorine-
based disinfectants (bleach). The alternative
agents are often promoted as less toxic,
environmentally friendly, and natural. The need
for disinfectants as part of sanitation procedures
has been supported by studies that show
a For a discussion of traditional disinfectants and
sanitizers, including definitions, please see the
NCCEH evidence review on Disinfectants and
Sanitizers for Use on Food Contact Surfaces.
2
cross-contamination risks from environmental and
food contact surfaces are not adequately reduced by
the use of detergents and washing alone.1
This document is intended for public health inspectors
and reviews the effectiveness, disinfection potential,
and pertinent issues of major types of alternative
agents that claim to have antimicrobial properties.
Alternative agents that are reviewed include: tea tree
oil, thyme oil, electrolyzed water, ozonated water,
silver-based products, vinegar (acetic acid), lemon
juice (citric acid), baking soda (sodium bicarbonate),
and microfibre cloths. Table 1 summarizes the
advantages and disadvantages of each alternative
agent reviewed.
Unlike registered disinfectants, many alternative
agents do not have a drug identification number (DIN).
The lack of a DIN indicates that product safety and
effectiveness have not been formally reviewed and
approved by Health Canada. Therefore, it may be
difficult for public health inspectors (PHIs) to advise
the public on the efficacy and safety of these
alternative agents. Although uncommon, some
alternative agents, such as thyme oil, silver, and citric
acid are primary active ingredients in approved hard
surface disinfectants. However, it is important to note
that the antimicrobial efficacy of these alternative
agents may be potentiated by other chemical
compounds present in such registered disinfectants.
Therefore, evaluating the efficacy of standalone
alternative agents is likely not representative of results
obtained using products in which a combination of
ingredients, in addition to an alternative agent, is
tested. Registered disinfectants can be found in
Health Canada’s Drug Product Database.2
Table 1. Summary of notable advantages and disadvantages of alternative antimicrobial agentsb
Alternative
agent Advantages Disadvantages
Primary active
ingredient of at
least one
Health Canada
registered
disinfectant Conclusions
Tea tree oil Natural product
Defined International
Standards for
composition of tea tree
oil
TTO is used in existing
topical medicinal
treatments
No special equipment
required to use
Significant oral toxicity
May cause adverse skin
reactions
Insoluble in water (may
leave film of oil if used
on hard surfaces)
No Effective
antimicrobial, but
oral toxicity and
hydrophobic
properties limits its
use as a sanitizer
Thyme oil Natural product
Generally Recognized
as Safe (GRAS status)
Low toxicity
Environmentally friendly
Some bacteria are
resistant to thyme oil
(e.g., P. aeruginosa, S.
aureus)
Thymol is listed as an
asthmagen by the
Association of
Occupational and
Environmental Clinics
(AOEC)
Expensive
Requires long contact-
time (10 minutes)
Yes Promising
antimicrobial
properties for use as
a sanitizer
High cost may limit
uses for large-scale
applications
b A brief discussion, including references, for the advantages and disadvantages in this table is available within the reviews for
each alternative antimicrobial agent.
3
Alternative
agent Advantages Disadvantages
Primary active
ingredient of at
least one
Health Canada
registered
disinfectant Conclusions
Electrolyzed
water
(EO water)
Only salt and water
required for production
of EO water
On-site generation
eliminates need for
transport, storage, and
handling of hazardous
chemicals
Abundantly and readily
produced
Low operating costs
No toxic/chemical
residues left on surfaces
Acidic EO water has
corrosive properties
Safeguards are required
as chlorine gas
produced in production
chambers
High startup and
maintenance costs
(special equipment for
production and
dispensing required)
Rapid dissipation of
antimicrobial activity
No Promising
antimicrobial
properties for use as
a sanitizer
Potential to be used
for large-scale
applications
Ozonated
water
(aqueous
ozone)
Only oxygen (e.g., in air
or compressed) required
for production
On-site generation
eliminates need for
transport, storage, and
handling of hazardous
chemicals
Devices have been
registered with NSF
International and the
Canadian Food
Inspection Agency
U.S. Food and Drug
Administration has
approved ozone (gas
and aqueous phase) as
an antimicrobial
Maintains efficacy in
cold water
Abundantly and readily
produced
No toxic/chemical
residues left on surfaces
High startup, operating,
and maintenance costs
(special equipment for
UV or corona discharge,
dispensing, etc.)
Potential occupational
exposure to ozone
Damaging to sensitive
materials
Rapid dissipation of
antimicrobial activity
No Promising
antimicrobial
properties for use as
a sanitizer
Potential to be used
for large-scale
applications
Silver Existing uses of silver in
drinking water,
swimming pools,
medical devices
Numerous potential
applications for silver-
impregnated materials/
nanotechnology
Demonstrated residual
Slow-acting
antimicrobial
Microbial resistance has
been identified
Interference by proteins
and salts
Low toxicity at levels
needed for antimicrobial
Yes Research shows
potential for
numerous
applications as an
antimicrobial agent
More research is
needed to define the
parameters required
to be effective
4
Alternative
agent Advantages Disadvantages
Primary active
ingredient of at
least one
Health Canada
registered
disinfectant Conclusions
antimicrobial activity activity
Loses antimicrobial
properties once all silver
ions have been released
Applications may be
limited to residual
antimicrobial activity
(i.e., non-immediate
uses)
Vinegar
(acetic acid)
Lemon juice
(citric acid)
Baking soda
(sodium
bicarbonate)
Natural product
Readily available and
abundant
Low toxicity
Limited antimicrobial
efficacy and narrow in
spectrum
May damage the
organoleptic properties
of produce
May be corrosive or
irritating
Has pungent and
unwanted odours
Mixing acids with bleach
can cause the
production of chlorine
gas
Acetic acid: No
Citric acid: Yes
Sodium
bicarbonate:
No
Applications are
limited by poor
antimicrobial efficacy
and aesthetic
considerations
Potential to be used
in formulations of
disinfectants
Unlikely to be used
for commercial
applications, but
may have uses in
domestic settings
Microfibre Readily available
More effective at
cleaning than cotton
fabrics
Lighter material can
promote productivity and
reduce occupational
injury
May minimize the use of
chemicals
Can be cost effective
Lacks active
antimicrobial properties
may become a source
of contamination for
subsequently cleaned
surfaces
Damaged by heat,
chlorine-based
disinfectants, and fabric
softeners
More expensive than
cotton
No Promising efficacy
for cleaning, but not
as an antimicrobial
Tea Tree Oil
This essential oil, extracted from the leaves of
Melaleuca alternifolia, is widely used as an alternative
antimicrobial agent and international standards for the
composition of tea tree oil (TTO) have been
developed (e.g., ISO 4730).3 It is often used as a
topical anti-inflammatory agent and to treat skin
infections such as acne, ringworm, scabies, and
athlete’s foot.4,5
The hydrophobic properties of TTO are hypothesized
to impair cell membrane integrity. Supporting studies
have revealed the effects of TTO on bacterial and
fungal cells, demonstrating the leakage of intracellular
components, inhibition of cellular respiration, and an
increase in susceptibility to sodium chloride.4,6,7
Available research has suggested the potential for
antiviral and antiprotozoal activity, but studies have
been limited in scope.4 Terpinen-4-ol has been noted
as the primary antimicrobial agent in TTO, but several
other components are also microbicidal or facilitate
antimicrobial activity.4,6
5
Antimicrobial efficacy
Researchers have used European Standards for
evaluating the use of TTO as a sanitizer for food
areas (EN 1276) and as an antiseptic agent for hand
washing (EN 12054).8 The minimum standard is a 5
log reduction in 5 minutes for use as a sanitizer and a
2.52 log reduction in 1 minute for use as a hand
washing agent. Test suspensions of Staphylococcus
aureus, Escherichia coli, and Pseudomonas
aeruginosa were treated with 1% to 10% (v/v) TTO
and log reductions were recorded after 1 minute and 5
minutes of treatment.8 Treatment with 5% TTO
resulted in a 5 log reduction of E. coli in 1 minute and
a 4 log reduction of P. aeruginosa in 5 minutes.
Treatment with 8% TTO resulted in a 5 log reduction
of P. aeruginosa in 1 minute. Log reductions of S.
aureus ranged from 0.19 (1% TTO, 1 minute) to 0.80
(10% TTO, 1 min) and did not significantly differ with
varying concentrations of TTO or contact time.8 As an
antiseptic hand wash agent, 2.75% TTO resulted in
the reduction of E. coli and P. aeruginosa by 4 logs
and 2 logs, respectively, in 1 minute; the same
treatment resulted in a log reduction of <0.5 for S.
aureus.8 Other studies have determined minimum
inhibitory concentrations for E. coli and S. aureus to
be 0.25% and 0.50% (v/v), respectively.9
Potential use for disinfection:
applicability and pertinent issues
Ingestion of undiluted TTO may induce temporary
neurological effects in children and adults. Symptoms
include confusion, inability to walk, disorientation,
ataxia, unconsciousness, and coma.5,10 Allergic skin
reactions, systemic reactions, and irritation are also
associated with dermal exposure to TTO. The LD50 of
tea tree oil is estimated to be 1.9-2.6 mL/kg in rats
and when used undiluted has been determined to be
unsafe by scientific committees of the European
Commission; it can be irritating to the skin at
concentrations as low as 5% (v/v).11 Therefore, uses
of TTO on food contact surfaces and in settings with
sensitive individuals may be limited by its oral and
dermal toxicity to humans.
There also exists preliminary evidence that indicate
the potential for TTO as an endocrine disruptor,
altering the signalling of sex hormones that affect
human development.12 In particular, one clinical report
has suggested that pre-pubertal gynecomastia, the
abnormal growth of breast tissue in preadolescent
males, may be related to the repeated use of personal
products containing lavender oil and/or lavender oil
combined with TTO (both are essential oils).13,14
Investigations through mammalian cell culture studies
have revealed that TTO has slight “estrogenic and
antiandrogenic activities”.12,13,15 However, another
study emphasizes the need to consider bioavailability
when conducting human health risk assessments and
that the aforementioned in vitro results are unlikely to
represent in vivo human health risks.15 Results from
this study supported the in vitro estrogenic and
antiandrogenic effects of TTO, but also illustrated that
TTO components, known to penetrate the skin, do not
induce measurable effects.15 From this, the report
suggests that further human health risk assessments
regarding TTO should characterize TTO components
and their bioavailability, in conjunction with
observations for possible estrogenic and/or
antiandrogenic properties. Furthermore, threshold
levels of TTO required to induce these effects have
yet to be characterized. More evidence is required in
order to evaluate these potential health effects and
their significance, if any, to the population and to
public health.
Thyme Oil
Thymol and carvacrol are the main components in
thyme oil that are believed to exhibit the most
antimicrobial activity.16 They have been demonstrated
to cause an increase in permeability of the cell
membranes of bacteria, a reduction in the proton
motive force, and an associated decrease in
intracellular levels of adenosine triphosphate (ATP, a
high-energy molecule responsible for providing energy
to drive reactions in the cell).17,18 Although there is
insufficient evidence to support its effectiveness for
health benefits, thyme oil has been taken orally to
treat sore throat, cough, bronchitis and inflammatory
conditions of the gastrointestinal tract.19 As a topical
agent, it can be used as an anti-inflammatory
mouthwash and for treatment of ear infections. Thyme
oil is also a food additive and, in the United States, is
Generally Recognized as Safe (GRAS) for ingestion
(21 CFR 182.10).20
Antimicrobial efficacy
At concentrations of 0.1 to 0.6% (v/v), thyme oil is
shown to inhibit the growth against microorganisms,
such as Campylobacter jejuni, E. coli O157:H7,
Listeria monocytogenes, Salmonella spp., S. aureus,
and Candida albicans; however, much higher
concentrations (e.g., 2 to 10%) are needed to be
6
bacteriostatic against P. aeruginosa.16,21-23 When
compared to tea tree oil, thyme oil has been shown to
have a lower minimal inhibitory concentration (MIC) to
a variety of microorganisms.22,23 A 5 log reduction in
E. coli was observed within 5 minutes of exposure to
0.31% thyme oil whereas the same reduction in S.
aureus took 15 minutes with 2.5% thyme oil.23
Populations of P. aeruginosa did not achieve this
reduction even after 24 hours of exposure to >10%
thyme oil.
Potential use for disinfection:
applicability and pertinent issues
Thyme oil is natural, environmentally friendly, and has
been used as a primary active ingredient in several
disinfectant products registered with Health Canada.
Classified as a Minimum Risk Pesticide, it has low oral
and dermal toxicity, allowing it to be exempt from
some sections of the U.S. Federal Insecticide,
Fungicide, and Rodenticide Act and pesticide
registration requirements.24 Also, some thymol-based
registered disinfectant products do not require a
rinsing or wiping step for disinfecting surfaces and can
be safely used undiluted.25 However, thymol is listed
as a sensitizer and asthmagen by the Association of
Occupational and Environmental Clinics (AOEC).26
Furthermore, the long contact times for required
disinfection (e.g., 10 minutes) may inhibit its use for
large-scale applications.
Electrolyzed Water
(Electrolyzed Oxidizing Water)
Although the mechanism has not been fully described,
this method of disinfection has been hypothesized to
rely on the chlorine-based disinfection properties of
hypochlorous acid (free chlorine) produced by the
electrolysis of a salt (sodium chloride) solution.27 In
addition, studies have shown that electrolyzed
oxidizing water (EO water) is more effective at
inactivating microbes than chlorine solutions with
similar free chlorine concentrations, suggesting that
oxidation reduction potential (ORP) and low pH, in
addition to free chlorine, may be synergistic to the
antimicrobial activity of EO water.28 Typically, acidic
EO water has a free chlorine level of 10 to 90 ppm,
ORP of 1100 mV, and a pH of 2 to 3.27,29 Neutral (pH
6 to 8) and alkaline (pH 10 to 13) forms of EO water
can also be produced by increasing the concentration
of hypochlorite ions (OCl-); this may be done to reduce
its corrosiveness.27
Antimicrobial efficacy
EO water has been tested for efficacy of use in
numerous applications, such as washing produce,
decontamination of egg shells (>6 log reduction in
Salmonella enteritidis in 1 minute), and
decontamination of hides of cattle (3.5 log reduction in
aerobic plate count, 4.3 log reduction in
Enterobacteriaceae count, 47% reduction in number
of hides testing positive for E. coli O157:H7).30-32 EO
water has been shown to be effective at inactivating a
variety of microorganisms of public health
significance. Suspensions of E. coli O157:H7, S.
enteritidis, P. aeruginosa, C. jejuni, S. aureus, L.
monocytogenes have shown to be inactivated by
approximately 7 logs in 1 minute or less after
treatment with EO water.28,33,34 The efficacy of EO
water on food contact surfaces, produce, poultry, fish,
and pork have also been reviewed.29 Summary of the
findings indicate test organisms were reduced by log
reductions of 2.0-6.0 for hard surfaces/utensils, 1.0-
3.5 for vegetables/fruits, 0.8-3.0 for chicken
carcasses, 1.0-1.8 for pork, and 0.4-2.8 for fish.29
These reductions represented treatments with contact
times ranging from less than 1 minute to 20 minutes,
in some cases.29 Furthermore, washings obtained
from inoculated stainless steel and glass surfaces,
after treatment with EO water, have been found to
contain <1 log CFU/mL of test organisms, illustrating
the potential for EO water to reduce cross
contamination from the processing water.35
Potential use for disinfection:
applicability and pertinent issues
Besides the antimicrobial efficacy of EO water, the low
operating costs from the availability of salt and water
make EO water a promising alternative disinfectant.
However, there is a high initial cost for installing
special equipment to produce and dispense EO water.
As no residue or noxious gas remains after application
of EO water, the agent is noted to be environmentally
and worker friendly.32 Also, on-site generation of EO
water eliminates the need for special transportation,
handling, or storage of hazardous chemicals.29
However, rapid dissipation of antimicrobial activity
may prevent EO water solutions from being stored in
an open environment for extended periods. Corrosion
of certain metals (e.g., carbon steel, copper) has also
been noted in certain studies; this can be minimized
by using neutral EO water.36 Furthermore, chlorine
gas may be generated in the anode chamber during
production of EO water and the appropriate
7
safeguards and response measures must be present
should leakage occur.27 The toxicity of EO water has
also been noted as lower than that of conventional
disinfectants and no adverse oral or digestive health
effects were observed in mice given EO water as
drinking water.32,37
Similar to chlorine-based sanitizing treatments,
microbial reduction may vary depending on the
susceptibility of test organisms, contact time,
treatment methodology, presence of organic
residues/debris, and the surface/texture of the area
being sanitized. The presence of organic residues,
uneven textures, and porous surfaces has been
demonstrated to impair the antimicrobial efficacy of
EO water.38,39 Studies have also shown inactivation of
microbes to be dependent on temperature of EO
water, for example, EO water at 45°C favours
microbial inactivation when compared to EO water at
23°C.33
Ozonated Water (Aqueous
Ozone)
Ozone (O3), a gaseous oxidizing agent with
antimicrobial properties, can be generated on-site and
dissolved into water to create an ozone enriched
water solution. Potential uses of ozonated water
include washing and extending the shelf life of
produce, decontaminating and lowering the chemical
oxygen demand of processing waters, sanitation of
hard surfaces, and decontamination of cattle
hides.31,40-43 However, ozone is highly unstable and
has limited solubility in water.42 Therefore, the
antimicrobial activity of ozonated water dissipates
rapidly and may limit its applications for non-
immediate uses.
In 2001, the U.S. Food and Drug Administration
approved ozone to be used as an “antimicrobial
agent” and in the “treatment, storage, and processing
of foods” as outlined in the U.S. Code of Federal
Regulations (21 CFR 173.368).44 NSF international
has registered devices deemed “acceptable for use as
an ozone generating device providing sanitation and
disinfection to hard, inanimate, pre-cleaned surfaces,
in and around food processing areas.”45 Furthermore,
the Canadian Food Inspection Agency (CFIA) has
deemed several devices that produce ozonated water
for sanitizing hard surfaces as acceptable for use in
establishments under their regulatory authority (i.e., a
federally registered food processor). Such devices are
listed in the searchable database, Reference Listing of
Accepted Construction Materials, Packaging Materials and
Non-Food Chemical Products
Antimicrobial efficacy
.46
Lettuce dipped in ozonated water (4 ppm O3, 20°C) for
2 minutes had significant reductions in
Enterobacteriaceae (1.3 log CFU/g) as well as
psychrotrophic (1.5 log CFU/g) and mesophilic
bacteria (1.7 log CFU/g).43 These results were
comparable to treatment with 100 ppm chlorine in the
same conditions and researchers have suggested that
ozonated water may be a potential alternative to
chlorine dippings.43 Use of ozonated water in place of
chlorine in produce processing may avoid the
formation of undesirable chlorine disinfection by-
products (e.g., trihalomethanes). When used to
decontaminate cattle hides, ozonated water was able
to achieve a 2.1 log reduction in aerobic plate count,
3.4 log reduction in Enterobacteriaceae count, and
58% reduction in number of hides testing positive for
E. coli O157:H7.31
Researchers have also used European Standards EN
1040 and EN 1275 to determine the bactericidal and
fungicidal efficacy of ozonated water.47 Test
suspensions of S. aureus, E. coli, P. aeruginosa, and
Enterococcus hirae were inactivated (>5 log
reduction) in 30 seconds when treated with ozonated
water with a concentration of 3 ppm O3; test
suspensions of C. albicans were inactivated (>4 log
reduction) under similar treatment conditions.47 No
reduction in the number of viable spores of Aspergillus
brasiliensis was observed, even after treatment with
ozonated water (1.5 to 3 ppm O3) for 30 minutes.
Furthermore, a reduction in approximately half of the
ozone concentration (e.g., 3.0 ppm to 1.5 ppm) was
observed after 30 minutes of storage. Lower
concentrations of ozone (e.g., 0.15 to 0.20 ppm O3) in
water can achieve comparable log reductions but
contact time of 1-5 minutes is required.48
Potential use for disinfection:
applicability and pertinent issues
Ozonated water has strong non-selective antimicrobial
properties, leaves no chemical residues, can be used
with cold water, and can be produced on demand.
Furthermore, on-site generation of ozonated water
avoids the need for special transportation, handling,
and storage of hazardous chemicals. However, in
order to produce ozonated water, high energy UV
radiation (e.g., 188 nm wavelength) or electrical
8
discharges (e.g., corona discharge) are required to
convert oxygen in the air (or pure oxygen) into ozone
gas.42 These processes require special equipment
and substantial amounts of electrical energy to
operate, leading to high initial and operating costs for
large-scale commercial applications.
Limited information exists on the toxicity of ozonated
water, but studies have shown no significant adverse
effects on human oral epithelial cells after acute
exposure.49 Other potential limitations for its use
include damage to sensitive materials (e.g., rubber
gaskets) and occupational safety associated with
exposure to ozone gas.42,49
Silver
Studies have shown that the likely modes of microbial
inactivation by silver is through interference with
cellular respiration and transport, interactions with
DNA, disruption of proteins, and destruction of the cell
membrane.50 Contrary to many disinfectants, potential
applications of silver are commonly associated with
slow release of silver from silver-impregnated
materials and residual antimicrobial effects.51
Silver has been used for its antimicrobial properties in
drinking water/cooling tower disinfection, swimming
pools, and for medical uses.52 Notably, Health Canada
has issued a DIN for a silver dihydrogen citrate-based
disinfectant (silver dihydrogen citrate 0.003% and
citric acid 4.846%) for use as a hard surface
disinfectant with demonstrated residual activity.53
Antimicrobial efficacy
Antimicrobial efficacy of silver-impregnated packaging
liners on spoilage organisms from meats and melons
has also been evaluated.54,55 For meat liners, an
average difference of 1 log CFU/g was observed
between silver-impregnated pads and control pads.
For melon liners, an average difference of 3 log
CFU/g was observed between silver-impregnated
pads and control pads. As silver has an affinity for
proteins and salts, meat exudates likely interfere with
the antimicrobial activity of silver to a greater extent
than melon juices.55
Several silver-impregnated wound dressings have
also been evaluated for bactericidal efficacy.56
Notably, antimicrobial activity may depend on release
rate of silver from the impregnated material, as well as
the matrix type. For example, it has been
demonstrated that a 24-hour silver release rate of
approximately 93 ppm can result in >3.46 log
reduction (30 min contact time) in S. aureus.56
However, with a dressing of a different matrix type, no
log reduction was observed (30 min contact time)
even though the dressing had a higher 24-hour silver
release rate of 318 ppm.
In one study, stainless steel coupons and cups were
coated with a silver-zinc zeolite (2.5% w/w silver and
14% zinc), then inoculated with test organisms (e.g.,
S. aureus, E. coli, P. aeruginosa, and L.
monocytogenes) to evaluate bactericidal activity by
recovery of organisms at different time intervals (e.g.,
0h, 4h, 24h). Microbial reduction of up to 5 logs was
observed in 24 hours, when compared to untreated
controls.57 Microbial reductions observed at 4h
diminished after 5 washings with a towel, but
reductions at 24h remained >90% after 11 washings.57
A similar study using the same silver-zinc zeolite
coatings showed that the numbers of vegetative cells
of B. cereus were reduced by 3 logs after 24h, but
spores were not inactivated even after 48 hours.58
Furthermore, an alcohol-based (79%) disinfectant
spray with silver iodide (0.005%) was tested for
residual bactericidal activity. When compared to
untreated controls, populations of P. aeruginosa and
S. aureus were reduced by >3 logs in 2 hours and by
>4 logs in 8 hours; a chlorine based disinfectant
showed similar residual activity, but only with S.
aureus.59 Multiple rinses, abrasion, and re-
contamination did not affect residual activity.
Potential use for disinfection:
applicability and pertinent issues
Accumulation of silver in the body may lead to side
effects including: impaired absorption of medicine,
neurological problems, kidney damage, headache,
fatigue, and skin irritation.60 However, the levels of
silver in silver-based antimicrobial products have not
been documented to cause adverse effects in humans
and are unlikely to cause the side effects associated
with chronic ingestion of high levels of colloid silver
products, which may lead to argyria (an irreversible
condition which manifests as blue discolouration of
the skin and/or eyes).60-62 Silver has no known
function in the body and health claims associated with
the use of colloid silver products have yet to be
substantiated.60 For a discussion on nanosilver
technologies, please see the NCCEH contracted
review by Green and Ndegwa (2011) titled:
9
Nanotechnology: A Review of Exposure, Health Risks, and
Recent Regulatory Developments.63
The World Health Organization (WHO) has suggested
that the NOAEL of silver in drinking water to be 10 g
consumed over a lifetime (i.e., daily ingestion of 2 L of
water containing 0.2 mg/L silver for 70 years).64
Importantly, the levels of silver in natural waters and
drinking water have been noted to be thousands, if not
millions, of times lower than the NOAEL (e.g.,
5 µg/L).64
Other issues noted with the use of silver as an
antimicrobial include: the emergence of silver-
resistant microbes (e.g., cellular efflux pumps),
interference from proteins and salts, current lack of
standardization for efficacy testing, and loss of
antimicrobial properties once all active silver is
released from impregnated materials.52,65-67 Also, the
slow-acting antimicrobial activity of silver limits its use
for immediate disinfection of hard surfaces.
Nevertheless, the residual antimicrobial activity of
silver may allow for potential applications in
formulations of disinfectants or to reduce the
harbourage of microbes on surfaces and subsequent
transfer of microbes from one surface to another.
Vinegar (acetic acid), Lemon
Juice (citric acid), and Baking
Soda (sodium bicarbonate)
The antimicrobial properties of vinegar and lemon
juice are commonly associated with their acetic acid
and citric acid content, respectively.68 These organic
acids are hypothesized to cross the cell membrane of
bacteria where the release in protons (H+) causes the
cells to die.69 As the growth of many pathogenic
organisms are inhibited in conditions where the pH is
<4.6, these organic acids, with a pH 2 to 3, are
commonly added to foods as a preservative.69
Baking soda has been used to formulate toothpaste,
cosmetic products, and is known for its acid-
neutralizing properties, but limited peer-reviewed
evidence exists for its antimicrobial activity on hard
surfaces.70 It has been reported to be virucidal and
inhibit the growth of several fungi, but its mechanism
of action is unclear.71,72 Baking soda has also been
shown to enhance the effectiveness of other agents
for controlling mould growth on produce, but its
antifungal spectrum may be limited.73-77 In addition,
because the pH of baking soda in a neutral solution
equilibrates at a maximum near 8.34, its pH alone is
likely insufficient to inhibit the growth of many
foodborne microorganisms, many of which can grow
in conditions with up to pH 9 to 10.70,78 However, at
least one study has suggested its chemical properties
(e.g., alkaline pH, mild abrasive) can be effective for
cleaning kitchen surfaces.79
Antimicrobial efficacy
Numerous studies have demonstrated the
antimicrobial efficacy of acetic acid (AA), citric acid
(CA), and sodium bicarbonate (SB) using suspensions
of bacteria, recovery from treated hard surfaces,
rinsing meat, and washing produce (summarized in
Appendix A).68,80-92 However, it is difficult to compare
results between studies as there are no standardized
experimental parameters used to test efficacy.
Notably, efficacy demonstrated in suspensions are
drastically different from efficacy demonstrated on
produce (i.e., in the absence or presence of organic
matter).
Results from studies suggest that vinegar (acetic acid)
exhibits the most antimicrobial efficacy, followed by
lemon juice (citric acid) and baking soda (sodium
bicarbonate).68,90 Typically, Gram-negative bacteria,
such as Shigella sonnei, Salmonella spp., E. coli, P.
aeruginosa, and Yersinia enterocolitia are more
susceptible to organic acids (e.g., acetic acid, citric
acid) than Gram-positive bacteria, such as S. aureus
and L. monocytogenes. The highly cross-linked cell
walls of Gram-positive bacteria are believed to impair
the diffusion of the organic acids into the cell,
preventing antimicrobial action.68,69,83 Baking soda is
generally ineffective against E. coli, P. aeruginosa, S.
aureus, and Salmonella spp., but had notable virucidal
activity against feline calicivirus (norovirus
surrogate).68,72,89 The efficacy of AA, CA, and SB vary
greatly (<1 log to >5 log reduction in test microbes;
contact times ranged from 0.5 min to 15 min)
depending on test organisms and test conditions.
When used at higher temperatures, vinegar and
lemon juice are observed to result in increased
antimicrobial efficacy.68,91,93 The difficulty in assessing
antimicrobial efficacy and narrow antimicrobial
spectrum of these alternative agents may limit their
applications as hard surface disinfectants.
Potential use for disinfection:
applicability and pertinent issues
Vinegar, lemon juice, and baking soda have the
advantage of being readily available, environmentally
10
friendly, low in toxicity, and natural. Although these
agents are commonly used to eliminate odours,
residual odour and taste on surfaces may be
unwanted in applications where public or occupational
exposure is undesirable, especially at concentrations
that exhibit antimicrobial activity. Organoleptic
properties of produce washed with AA or CA may also
be adversely affected (e.g., wilting or souring).90
Furthermore, like chlorine-based disinfectants, the
efficacy of organic acids (AA and CA) is drastically
reduced in the presence of organic matter. Potential
safety concerns are also noted with the use of
vinegar, lemon juice, and/or baking soda for sanitation
purposes. For example, if chlorine-based disinfectants
(e.g., bleach) are used simultaneously with vinegar
and/or lemon juice to sanitize hard surfaces, there is
potential for an increased risk of accidental mixing,
which may result in the formation of chlorine gas.
Designated containers (e.g., spray bottles or buckets)
with proper labelling would be necessary, as with all
chemical disinfectants, to indicate the contents and
reduce the chance of mixing incompatible chemicals.
The low pH of AA and CA can also make these
agents a potential eye, nose, and respiratory tract
irritant.
Overall, it is unlikely that vinegar, lemon juice or
baking soda, by themselves, will become mainstream
antimicrobial agents in commercial settings, but the
notable efficacy of vinegar and lemon juice may have
indications for their potential use as household
antimicrobial agents or in formulations of disinfectants.
Microfibre Cloths
Microfibres are extremely fine strands of fibres that
are less than 1 denier (i.e., a single strand weighs
1 gram per 9,000 metres). Due to the unique
structure of the fibres, micrometre diameters, and
electrostatic properties, the fabrics made from
microfibres have an ability to trap dust and microbes
more effectively than conventional cotton cloths or
mops; this is likely attributed to the high surface area
and capillary effect of microfibre fabrics.94,95
Depending on the weave and composition of the
fibres, properties of water absorption, permeability,
stain-resistance, and wrinkle-resistance can vary.
Antimicrobial efficacy
The fibres themselves have not been shown to be
microbicidal, but have been shown to demonstrate
considerable cleaning efficacy, by physical removal of
microbes and organic debris from surfaces.95-97 For
example, microfibre cloths (with water) have been
documented to reduce S. aureus, E. coli, and
Clostridium difficile spores on hard surfaces, by an
average of 1 to 3 logs.97,98 However, it is difficult to
make general statements regarding efficacy due to
the lack of standardized testing methods and
manufacturing parameters for microfibre cloths. Even
so, the application of microfiber cloths/fabrics for
cleaning may help maximize the effectiveness of
conventional antimicrobial products.
Potential use for cleaning:
applicability and pertinent issues
Although microfibre cloths are more expensive than
cotton cloths, the U.S. Environmental Protection
Agency has a case study to demonstrate that the use
of microfibre mops, in place of conventional mops in
hospital cleaning programs, can be more economical
by saving on labour, chemical, water, and electrical
costs.99 However, the cleaning efficacy of microfibre is
reduced through damage that can be caused by high
heat (e.g., process temperatures of industrial washing
machines), some disinfectants (e.g., bleach), and
fabric softeners.95,98,99 In addition, studies have
emphasized that the lack of antimicrobial properties
allows for the potential for cross-contamination or re-
contamination of subsequently cleaned surfaces if
used with water alone (i.e., transmission of diseases
in institutional and food processing settings).88,96,100,101
Evidence Gaps
The emergence of new alternative antimicrobial
agents and their use for disinfection requires further
research and review. The current lack of standardized
evaluation criteria makes it difficult to compare
antimicrobial properties across different types of
alternative agents. In particular, more research is
required to better define the concentration, contact
time, and stability required for these agents to induce
antimicrobial effects, if any. In addition, defining the
composition of alternative agents will help with
comparison. If alternative agents are considered for
use on food contact surfaces, the need for a final
rinsing step must also be evaluated.
Further understanding of the antimicrobial
mechanisms of alternative agents may help to define
relevant properties for use as disinfectants. For
example, how are they affected by organic residues or
other chemicals? How can they be made or used
11
more effectively? Do they possess potential or
synergistic properties when combined with other
disinfectants? Do they exhibit unique properties that
are desirable (e.g., residual antimicrobial effects)?
Further research to explore their potential uses in
formulating novel disinfectants may help evaluate their
role, if any, in manufacturing disinfectant products with
desirable characteristics (e.g., lower toxicity,
economical, environmentally friendly).
Acknowledgments
We would like to thank Luz Agana, Joanne Archer,
Alan Brown, Nelson Fok, and Karen Wong-Petrie for
their valuable input and review of the draft document,
and Michele Wiens for library assistance.
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89. Rutala WA, Barbee SL, Aguiar NC, Sobsey MD, Weber
DJ. Antimicrobial activity of home disinfectants and
natural products against potential human pathogens.
Infect Control Hosp Epidemiol. 2000 Jan;21(1):33-8.
90. Vijayakumar C, Wolf-Hall CE. Evaluation of household
sanitizers for reducing levels of Escherichia coli on
iceberg lettuce. J Food Prot. 2002 Oct;65(10):1646-50.
91. Wu FM, Doyle MP, Beuchat LR, Wells JG, Mintz ED,
Swaminathan B. Fate of Shigella sonnei on parsley and
methods of disinfection. J Food Prot. 2000
May;63(5):568-72.
92. Karapinar M, Gonul SA. Removal of Yersinia
enterocolitica from fresh parsley by washing with acetic
acid or vinegar. Int J Food Microbiol. 1992 Jul;16(3):261-
4.
93. Virto R, Sanz D, Alvarez I, Condon, Raso J. Inactivation
kinetics of Yersinia enterocolitica by citric and lactic acid
at different temperatures. Int J Food Microbiol. 2005 Sep
15;103(3):251-7.
94. Wren MWD, Rollins MSM, Jeanes A, Hall TJ, Coën PG,
Gant VA. Removing bacteria from hospital surfaces: a
laboratory comparison of ultramicrofibre and standard
cloths. J Hosp Infect. 2008;70(3):265-71.
95. Rutala WA, Gergen MF, Weber DJ. Microbiologic
evaluation of microfiber mops for surface disinfection. Am
J Infect Control. 2007;35(9):569-73.
96. Moore G, Griffith C. A laboratory evaluation of the
decontamination properties of microfibre cloths. J Hosp
Infect. 2006;64(4):379-85.
15
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16
Appendix A: Antimicrobial efficacy data of vinegar (acetic acid),
lemon juice (citric acid), and baking soda (sodium bicarbonate)
Organism Test conditions
Concentration (v/v, unless otherwise
indicated), contact time
(at 4 to 25°C unless otherwise indicated) Log reduction
(CFU/mL or g) Ref.
Aerobic plate
count Microflora on
lettuce Vinegar (1.9% acetic acid), 10 min w/ agitation 2.3 (Vijayakumar &
Wolf-Hall, 2002)90
Lemon juice (0.6% citric acid), 10 min w/
agitation 1.8
Microflora on
parsley 2 and 5% acetic acid solutions, 15 min 5 (Karapinar &
Gonul, 1992)92
Microflora on
cilantro Citric acid (0.6% prepared solution), 1 min <1 (Allende, 2009)81
Raw skinless/
boneless chicken
breast
Vinegar (5% acetic acid), 1 min w/ agitation 2.2 (McKee et al.,
2005)83
Baking soda (10% sodium bicarbonate
solution), 1 min w/ agitation 1.0
Escherichia coli
O157:H7 Suspension Vinegar (5% acetic acid), 5 min 2.4 (Rutala et al.,
2000)89
Baking Soda (8% sodium bicarbonate), 5 min 0.7
Vinegar (5% acetic acid), 1 min at 55°C >5.0 (Yang et al.,
2009)68
Citric acid (5% prepared solution), 10 min at
55°C >5.0
Baking Soda (11, 33, and 50% sodium
bicarbonate solution) <1
Inoculated lettuce Vinegar (5% acetic acid), 5 min 3.0 (Chang & Fang,
2007)87
Inoculated cilantro Citric acid (0.6% prepared solution), 1 min <1 (Allende, 2009)81
Escherichia coli
CDC1932
(nalidixic acid
resistant strain)
Inoculated
lettuce Vinegar (1.9% acetic acid), 10 min 5.4 (Vijayakumar &
Wolf-Hall, 2002)90
Lemon juice (0.6% citric acid), 10 min w/
agitation 2.1
Staphylococcus
aureus Suspension Vinegar (5% acetic acid), 5 min 0.3-2.3 (Rutala et al.,
2000)89
Baking Soda (8% sodium bicarbonate), 5 min 0.5
Salmonella
choleraesuis Suspension Vinegar (5% acetic acid), 0.5 min >6.0 (Rutala et al.,
2000)89
Baking Soda (8% sodium bicarbonate), 5 min 2.3
Salmonella
Typhimurium Suspension Vinegar (5% acetic acid), 1 min >5.0 (Yang et al.,
2009)68
Citric acid (5% prepared solution), 1 min at
55°C >5.0
Inoculated spring
onion and rocket
leaves
Lemon juice (4.2% citric acid), 15 min 2.95 (rocket
leaves), 1.70
(spring onion)
(Yucel Sengun &
Karapinar,
2005)85
Vinegar (3.95% acetic acid), 15 min 2.20 (rocket
leaves), 1.19
(spring onion)
(Yucel Sengun &
Karapinar,
2005)85
17
Organism Test conditions
Concentration (v/v, unless otherwise
indicated), contact time
(at 4 to 25°C unless otherwise indicated) Log reduction
(CFU/mL or g) Ref.
Inoculated carrots Vinegar (4.03% acetic acid), 15 min 1.87 (Yucel Sengun &
Karapinar,
2004)84
Lemon juice (4.46 citric acid), 15 min 2.68
Inoculated stuffed
mussels Lemon juice (5.88% citric acid), 15 min 0.56 (Kişla, 2007)82
Pseudomonas
aeruginosa Suspension Vinegar (5% acetic acid), 0.5 min >5.8 (Rutala et al.,
2000)89
Baking Soda (8% sodium bicarbonate), 5 min 1.1
Listeria
monocytogenes Suspension Vinegar (5% acetic acid), 1 min at 55°C >5.0 (Yang et al.,
2009)68
Vinegar (5% acetic acid), 10 min at 25°C
Citric acid (5% prepared solution), 10 min at
55°C
Yersinia
enterocolitica Suspension Citric acid (5% prepared solution), 10 min at
4°C <1 (Virto et al.,
2005)93
Citric acid (5% prepared solution), 10 min at
20°C <1
Citric acid (5% prepared solution), 2 min at
40°C >4
Citric acid (10% prepared solution), 10 min at
4°C <1
Citric acid (10% prepared solution), 10 min at
20°C >4
Citric acid (10% prepared solution), 1 min at
40°C >4
Inoculated parsley Vinegar (1.96 and 2.45% acetic acid), 15 min 5 (Karapinar &
Gonul, 1992)92
Shigella sonnei Inoculated parsley Vinegar (5.2% acetic acid), 5 min w/ agitation >6.0 (Wu et al., 2000)91
Poliovirus Suspensions Vinegar (5% acetic acid), 5 min 0.32 (Rutala et al.,
2000)89
Baking soda (8% sodium bicarbonate), 5 min 0.42
Feline
calicivirus
(norovirus
surrogate)
Inoculated stainless
steel disks Baking soda (5% sodium bicarbonate), 1 min 4 (Malik & Goyal,
2006)
Appendix A Table (cont’d)
18
Appendix B. Search Methodology
Literature searches were conducted to locate articles
that support a brief review and discussion of the
mechanism of action, disinfection potential, pertinent
issues, and safety/toxicity concerns of each
alternative antimicrobial agent. Bibliographies of
retrieved articles were scanned to further retrieve
more extensive and detailed information on a
particular subject of interest. Any related articles and
suggested articles, appearing within the search
engine, were also considered for inclusion. This
process subsequently aided in refining search
terminology and finding additional and specific articles
of interest.
Inclusion of articles, with publishing dates from years
2001-2011, were preferable; articles were not
excluded by date if their material was of particular
interest or the date of publication did not adversely
impact the quality of evidence. Grey literature was
included for descriptive and illustrative purposes.
Search engines/databases for
sources of information
University of British Columbia Library – ‘Summon
Search (publisher list here)
Pubmed
ScienceDirect
Ingentaconnect
MedlinePlus.
Search terminology
Names of each antimicrobial agent, including any
alternative names or parts of names, were used by
themselves or in combination with:
Action
Disadvantage
Activity Disinfect*
Advantage
Effectiv*
Adverse
Efficac*
Antimicrobial Food
Applica*
Germicid*
Bacteri*
Health effect
Biocid*
Mechanism
Characteristic
Microbicid*
Potential
Safety
Propert*
Surface
Review
Toxic*
Each alternative agent was reviewed on the basis of
antimicrobial activity against microorganisms
significant to public health; the emphasis was on
comparisons with similar bacteria. Microorganisms
included:
Escherichia coli O157: H7
Staphyloccocus aureus
Pseudomonas aeruginosa
Salmonella spp.
Campylobacter jejuni
Listeria monocytogenes
Shigella sonnei
Yersinia enterocolitica
Enterococcus hirae
Norovirus surrogates (feline calicivirus)
Aspergillus brasiliensis spores
Clostridium difficile spores
Candida albicans.
19
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... 27,28 Vinegar is often perceived as "safer" than traditional cleaning chemicals and is sometimes misrepresented as a "chemical-free" cleaner since it can be ingested. 29 The acetic acid in vinegar can evaporate, be inhaled, and act as an irritant, 30,31 as shown in a past study of a food processing facility using 4% acetic acid, where exposed workers demonstrated reduced spirometric performances. 32 Consumer-grade vinegar typically ranges in concentration from 4% to 8%, but published studies characterizing cleaning activities and associated exposures of domestic workers were not found in the literature. ...
... Additionally, adjusting work practices such as avoiding the use of sprays and decreasing cleaning solution concentrations would be expected to reduce workplace exposures. As an alternative to acetic acid, citric acid is a similar antimicrobial cleaning ingredient but is non-volatile, with reduced ability to be inhaled.31,[52][53][54] ...
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Associations between cleaning chemical exposures and asthma have previously been identified in professional cleaners and healthcare workers. Domestic workers, including housecleaners and caregivers, may receive similar exposures but in residential environments with lower ventilation rates. Study objectives were to compare exposures to occupational exposure limits (OELs), to determine relative contributions from individual cleaning tasks to overall exposure, and to evaluate the effects of ventilation and posture on exposure. Airborne chemical concentrations of sprayed cleaning chemicals (acetic acid or ammonia) were measured during typical cleaning tasks in a simulated residential work environment. Whole‐house cleaning exposures (18 cleaning tasks) were measured using integrated personal sampling methods. Individual task exposures were measured with a sampling line attached to subjects' breathing zones, with readings recorded by a ppbRAE monitor, equipped with a photo‐ionization detector calibrated for ammonia and acetic acid measurements. Integrated sampling results indicated no exposures above OELs occurred, but 95th percentile air concentrations would require risk management decisions. Exposure reductions were observed with increased source distance, with lower exposures from mopping floors compared to kneeling. Exposure reductions were also observed for most but not all tasks when ventilation was used, with implications that alternative exposure reduction methods may be needed.
... This study, however, considered high level of disinfection (minimum of 6-log reduction). A log reduction number of 6 means that for every one million starting number of CFUs, only one will remain after treatment (Fong et al., 2011;Health Canada, 2014). ...
... This study, however, considered high level of disinfection (minimum of 6-log reduction). A log reduction number of 6 means that for every one million starting number of CFUs, only one will remain after treatment (Fong et al., 2011;Health Canada, 2014). From this, the minimum dose required to decontaminate the textile material from A. niger was determined to be 1.26 kGy. ...
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To address the problem of biodegradation of fiber-based museum natural textiles, several decontamination methods are being used; the most common of which is chemical fumigation. However, the use of toxic chemicals presents not only occupational health hazards, but also challenges in terms of legal restrictions regarding environmental release and waste disposal. Methods that eliminate toxic pollutant release while offering low resource (energy and water) requirements and faster and effective treatment are desirable. This study investigated the use of gamma irradiation as an alternative fungal decontamination method for aged undyed 100% cotton fabric. Fabric samples inoculated with Aspergillus niger were irradiated at increasing doses of gamma radiation from a Co-60 source in the irradiation facility of the Philippine Nuclear Research Institute to determine its radiation sensitivity. The decimal reduction value (D10) was determined to be 0.21 kGy, which is sufficient to inactivate 90% of the total colony forming units initially obtained. The minimum dose required for high level disinfection (6-log reduction) of the textile material is 1.26 kGy. To determine the effects of gamma radiation to strength and color properties, fabric samples were irradiated at doses 0.1–25 kGy then subjected to breaking strength and elongation and color measurement tests. Physical property testing reveals that cotton fabrics of similar composition and construction as the one used in the study do not undergo significant degradation in terms of breaking strength up to 10 kGy dose. This may be regarded as the maximum dose of irradiation, which is well above the minimum dose of 1.26 kGy required to effectively decontaminate the textile material from A. niger. Gamma irradiation with cobalt-60 is an effective decontamination method for cotton fabrics that may be used for museum applications.
... Extensive research has demonstrated their wide range of favorable biological activities and thus, there has been a recent growth of interest in their application [2]. Fonget al. reported that Thyme plant (Thymus vulgaris L.) had exhibited favorable antibiotic properties and thus had been used since ancient times for treatment of sore throat, dry coughs, bronchitis, laryngitis and inflammatory conditions of the gastrointestinal tract, such as indigestion and gastritis [3,4]. Cristiani et al. have demonstrated that these biological effects, especially the strong antibacterial activity are mainly due to the existence of phenolic compounds such as thymol and carvacrol [2], with thymol being the major component of the thyme essential oil [3]. ...
... Thymol, like other essential oils is lipophilic, and thus is mostly accumulated and activated at the lipid bilayer of the cell membrane of bacteria [6]. It acts by disrupting the structure of the membrane and increasing the permeability of the cell [6], "causing a reduction in the proton motive force and an associated decrease in intracellular levels of ATP [4]", thus killing the bacteria. This, combined with Esmaeili et al. reports of other advantageous properties such as antioxidant properties [7] makes it a great component to be added to a wound dressing, and a much superior choice to other, more conventional antiseptics (such as silver) and antibiotics. ...
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Background: In developing new products for skin care and wound treatment, biocompatibility plays a major role in the choice of ingredients. Thymol, an essential oil extracted from thyme plant, exhibits outstanding antibacterial properties, but more importantly, it proves to be much more compatible to skin cells in comparison to some conventionally used antibiotic drugs and chemicals. Objective: The aim of the study was the use of thymol as an antibacterial and wound healing promoting agent in development of a novel wound dressing. Methods: The antibacterial properties of thymol before and after application in the dressing were analyzed by MIC and Disk Diffusion methods respectively. To ensure biocompatibility, MTT assay was used to assess the effect of thymol on skin fibroblast cells. In addition, effects of thymol on dressing's structure and its mechanical properties were studied by SEM and tensile strength tests respectively. Results: MIC investigation showed that thymol is capable of halting bacterial growth in concentrations as low as 156ppmdepending on the bacterial strain. Assessment of the product containing thymol by Disk diffusion method proved that the essential oil would retain its effectiveness when incorporated in the final product. Investigation of thymol's biocompatibility by MTT assay resulted in a rather unexpected outcome, thymol increased fibroblast cell growth significantly, but the exact amount could not be calculated due thymol's interference with the test material (MTT). Furthermore, increasing the concentration of thymol in the dressing increased its porosity and elongation on stress, but reduced its pore size and maximum stress. Conclusion: The observed data backed the original claim of antibacterial and wound healing properties, but also showed that incorporating thymol into the dressing increases its elasticity and porosity, but reduces its mechanical strength.
... Thymol has registered 30 times stronger antibacterial activity and 4 times lower toxicity compared to phenol, an antiseptic that can be found in several herbicides (Hajimehdipoor, 2010;Weber, 2004). Furthermore, thymol appears to disrupt the membrane structure and to increase the cell permeability, leading to a proton motive force diminution and decreased ATP intracellular levels, and hence, causing the death of the pathogen cell (Liolios et al., 2009;Fong et al., 2011). Another constituent present in essential oils composition is p-cymene, which seems to exhibit an antibacterial activity only when it is used with thymol and γ-terpinene, proving synergistic effects (Rota et al., 2008). ...
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Full-text available
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... Finally, to eliminate odors, neutralize some gases and disinfect hard surfaces; vinegar, zeolite, or baking soda as alternative microbiological agents can be used for routine cleaning of the vehicle (Fong et al., 2011). ...
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Environmentalists and a number of state agencies have recommended the use of 'green' products as alternatives to disinfectant cleaners. The alternative products most often cited are borax, vinegar, ammonia, and baking soda. None are registered with the U.S. Environmental Protection Agency as disinfectants or sanitizers. This study examines the ability of 'green' products to kill or eliminate representative Gram positive and Gram negative bacteria from nonporous surfaces. The antimicrobial activity of the products was assessed in the first phase of the study using laboratory tests which are required for EPA registration of antibacterial products. None of the alternative products demonstrated required levels of disinfectant activity against Staphylococcus aureus or Salmonella choleraesuis by the Association for Official Analytical Chemists (AOAC) Use Dilution Method. None of the 'green' products achieved required levels of sanitizing activity against S. aureus and Klebsiella pneumoniae in the EPA Non-Food Contact Sanitizer Test. The ability of 'green' products to kill and remove bacteria under in-use conditions was then examined using a method designed to include mechanical removal of bacteria from surfaces as a function of the disinfection process. Formica surfaces were contaminated with either S. aureus or Escherichia coli, dried, treated with a 'green' product, and mechanically scrubbed with a sterile, premoistened synthetic sponge. Bacteria were quantitatively recovered from the formica surface and the sponge, and recovery counts were compared to those of water alone and an EPA registered disinfectant. The 'green' products showed no significant reduction in bacterial levels on the surface and showed a high level of contamination transferred to the sponge. In contrast, the EPA approved disinfectant reduced counts on both the surface and the sponge to minimal or nondetectable levels for both types of bacteria.
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Advocates continue to promote the use of 'environmentally friendly' products/mixtures as alternatives for Environmental Protection Agency (EPA) registered disinfectants even though information regarding the effectiveness of the 'alternatives' is limited. This study investigates the ability of sodium hypochlorite bleach at the dilution recommended for disinfection of nonporous surfaces, and several 'alternatives' (ammonia, baking soda, borax, vinegar and a liquid dishwashing detergent) at concentrations in excess of normal recommendations for use, to kill and/or remove bacteria from surfaces. This study also explores the ability of these products to prevent the transfer of bacteria from one surface to another. Results of initial tests using a procedure required by the EPA for the determination of disinfectant efficacy of dilutable products, indicated that only bleach was effective against Staphylococcus aureus, Salmonella typhi, and Escherichia coli. These organisms represent the wide array of Gram positive and negative bacteria found on various surfaces. Although undiluted ammonia and vinegar also showed antimicrobial activity against the Gram negative organisms S. typhi and E. coli, none of the 'alternatives' were effective against the Gram positive bacteria, S. aureus. As the identity of bacteria on any surface is unknown by the consumer, the use of a disinfectant proven to have a broad spectrum of antimicrobial activity would be more prudent than using a substance having limited or no efficacy. A simulated use test using solutions of bleach, baking soda, borax, and the liquid detergent, as well as undiluted ammonia and vinegar against S. aureus and E. coli, also was performed. Antimicrobial activity, mechanical removal, and the transfer of organisms to a second surface during the simulated cleaning process were evaluated. The bleach exhibited the expected disinfectant efficacy by eliminating both test organisms from the original surface and the sponge, and preventing the transfer of the organisms to surrounding areas. Undiluted ammonia and vinegar were also effective, but only against E. coli. Again, none of the 'alternatives' were effective against S. aureus.
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The comparative effects of organic (citric and lactic) acids, ozone and chlorine on the microbiological population and quality parameters of fresh-cut lettuce during storage were evaluated. Dipping of lettuce in 100 mg L(-1) chlorine solution reduced the numbers of mesophilic and psychrotrophic bacteria and Enterobacteriaceae by 1.7, 2.0 and 1.6 log(10) colony-forming units (CFU) g(-1) respectively. Treatment of lettuce with citric (5 g L(-1)) and lactic (5 mL L(-1)) acid solutions and ozonated water (4 mg L(-1)) reduced the populations of mesophilic and psychrotrophic bacteria by 1.7 and 1.5 log(10) CFU g(-1) respectively. Organic acid dippings resulted in lower mesophilic and psychrotrophic counts than ozonated water and chlorine dippings during 12 days of storage. Lactic acid dipping effectively reduced (by 2.2 log(10) CFU g(-1)) and maintained low populations of Enterobacteriaceae on lettuce for the first 6 days of storage. No significant (P > 0.05) changes were observed in the texture and moisture content of lettuce samples dipped in chlorine, organic acids and ozonated water during storage. Colour, β-carotene and vitamin C values of fresh-cut iceberg lettuce did not change significantly (P > 0.05) until day 8. Lactic and citric acid and ozonated water dippings could be alternative treatments to chlorine dipping to prolong the shelf life of fresh-cut iceberg lettuce. Copyright © 2007 Society of Chemical Industry.
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In this laboratory study, several commercially available household bathroom and kitchen cleaning products, with and without EPA registered disinfectant properties, were compared to several 'alternative' products (lemon juice, vinegar, ammonia, baking soda and borax). High pressure decorative laminate tiles were cleaned mechanically using a Gardner Abrasion Tester. Test criteria included microbial reduction, based on remaining colony forming units of a tracer organism (Serratia marcescens), and soil reduction (of simulated bathroom and kitchen soil formulations) based on subjective grading by a panel of individuals. Among bathroom cleaners, the commercial cleaners and vinegar gave the most effective microbial reduction while a commercial cleaner without disinfectant was most effective at soil removal. Among kitchen cleaners, again the commercial products and vinegar were most effective at microbial reduction while the commercial cleaners and ammonia were most effective at soil removal.
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Baking soda (NaHCO3) or KHCO3 was found capable of significantly reducing the mycelial growth of Fusarium species. In Czapek Dox broth with baking soda or KHCO3 at as low as 0.2 g/100 mL, for example, the mycelial growth of Fusarium oxysporum 950 was inhibited by greater than 95%. The bicarbonate component of baking soda was responsible for the inhibitory effect.
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ABSTRACTASTM A-36 medium carbon steel, 110 copper, 3003-H14 aluminum, polyvinylchloride (PVC) type 1 and 304 stainless steel coupons were immersed in electrolyzed (EO) water, chlorine water, modified EO water and deionized water for a period of 8 days, and the properties of these types of water, weights and surface roughness of the coupons were monitored. EO water significantly increased (P < 0.05) the surface roughness of carbon steel, aluminum and copper with time; however, chlorine water, modified EO water and deionized water produced minimal changes on these materials. Regardless of the treatment water used, the surface roughness of stainless steel and PVC essentially remained the same. Carbon steel, copper, aluminum and stainless steel had a fair, good, good and outstanding corrosion resistance in EO water, respectively. Chlorine and modified EO water had a much less corrosive effect than EO water on all the materials tested.
Article
The efficacy of eight food additives as possible alternatives to synthetic fungicides for the control of soilborne pathogens, Fusarium oxysporum f. sp. melonis, Macrophomina phaseolina, Rhizoctonia solani, and Sclerotinia sclerotiorum was evaluated in this study. A preliminary selection of food additives was performed through in vitro tests. The ED50, minimum inhibition concentration (MIC), and minimum fungicidal concentration (MFC) values showed that ammonium bicarbonate and potassium sorbate were more toxic to soilborne pathogens compared to other food additives with few exceptions and, therefore selected for further testing in soil. The inhibitory and fungistatic efficacy potassium sorbate were higher than that of ammonium bicarbonate in in vitro tests. Potassium sorbate completely inhibited F. oxysporum f. sp. melonis, M. phaseolina, and R. solani at 0.6% in soil tests. In contrast ammonium bicarbonate at 0.6% was inferior compared to potassium sorbate. Ammonium bicarbonate achieved to control all fungi at 2% that is the highest concentration used in this study. Potassium sorbate showed higher toxicity to all fungi compared to ammonium bicarbonate in soil tests. Both ammonium bicarbonate and potassium sorbate increased the pH of soil. The rate of pH increase was higher in ammonium bicarbonate.