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Electrochemically activated solutions: Evidence for antimicrobial efficacy and applications in healthcare environments

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Due to the limitations associated with the use of existing biocidal agents, there is a need to explore new methods of disinfection to help maintain effective bioburden control, especially within the healthcare environment. The transformation of low mineral salt solutions into an activated metastable state, by electrochemical unipolar action, produces a solution containing a variety of oxidants, including hypochlorous acid, free chlorine and free radicals, known to possess antimicrobial properties. Electrochemically activated solutions (ECAS) have been shown to have broad-spectrum antimicrobial activity, and have the potential to be widely adopted within the healthcare environment due to low-cost raw material requirements and ease of production (either remotely or in situ). Numerous studies have found ECAS to be highly efficacious, as both a novel environmental decontaminant and a topical treatment agent (with low accompanying toxicity), but they are still not in widespread use, particularly within the healthcare environment. This review provides an overview of the scientific evidence for the mode of action, antimicrobial spectrum and potential healthcare-related applications of ECAS, providing an insight into these novel yet seldom utilised biocides.
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REVIEW
Electrochemically activated solutions: evidence
for antimicrobial efficacy and applications in healthcare
environments
R. M. S. Thorn &S. W. H. Lee &G. M. Robinson &
J. Greenman &D. M. Reynolds
Received: 13 April 2011 /Accepted: 15 July 2011
#Springer-Verlag 2011
Abstract Due to the limitations associated with the use of
existing biocidal agents, there is a need to explore new
methods of disinfection to help maintain effective bioburden
control, especially within the healthcare environment. The
transformation of low mineral salt solutions into an activated
metastable state, by electrochemical unipolar action, produces
a solution containing a variety of oxidants, including
hypochlorous acid, free chlorine and free radicals, known to
possess antimicrobial properties. Electrochemically activated
solutions (ECAS) have been shown to have broad-spectrum
antimicrobial activity, and have the potential to be widely
adopted within the healthcare environment due to low-cost
raw material requirements and ease of production (either
remotely or in situ). Numerous studies have found ECAS to be
highly efficacious, as both a novel environmental decontami-
nant and a topical treatment agent (with low accompanying
toxicity), but they are still not in widespread use, particularly
within the healthcare environment. This review provides an
overview of the scientific evidence for the mode of action,
antimicrobial spectrum and potential healthcare-related appli-
cations of ECAS, providing an insight into these novel yet
seldom utilised biocides.
Introduction
The use of biocides is an essential preventative control measure
against the spread of nosocomial infections and multiple drug-
resistant bacteria within hospital and other healthcare or
community settings. The general mechanism of action of
biocides involves multiple target sites, making them highly
efficacious as antimicrobials [1]. This reduces the risk of the
development of resistance to these agents, compared to that
associated with the use of antibiotics which usually only have
a single target site [2]. Acquired resistance to antibiotics is of
particular concern, as the number of antibiotic prescriptions is
again increasing within the UK [3]. Frequent use of several
existing biocides can cause respiratory or dermatological
health problems in hospital workers [46], for example,
following exposure to glutaraldehyde during the high-level
disinfection of heat-sensitive equipment such as endoscopes
[6]. Moreover, some have the potential to cause corrosion or
damage to equipment [7]. Therefore, there is still the need to
explore alternative biocides, particularly since there is
evidence for resistance to existing biocidal agents [8,9].
The use of electrolysis for disinfection has been employed
for over 100 years [10], although it was not until the 1970s
that the physicochemical properties of electrochemically
activated solutions (ECAS) were extensively researched at
the All-Russian Institute for Medical Engineering [11]. ECAS
have since found numerous biocidal applications, for exam-
ple, for potable water disinfection [12,13] and within the food
industry [14], and this is largely due to their high activity, use
of cheap raw materials and ease of production. With the
concern surrounding the emergence of antimicrobial resis-
tance in the healthcare environment, the use of ECAS has
been investigated for potential applications in clinical practice.
Generation of ECAS: the electrolytic cell and resultant
stability
ECAS are produced via the electrolysis of a low mineral
salt solution (the electrolyte) in an electrochemical cell
R. M. S. Thorn :S. W. H. Lee :G. M. Robinson :J. Greenman :
D. M. Reynolds (*)
Centre for Research in Biosciences, Department of Applied
Sciences, University of the West of England, Frenchay Campus,
Coldharbour Lane, Bristol BS16 1QY,UK
e-mail: Darren.Reynolds@uwe.ac.uk
Eur J Clin Microbiol Infect Dis
DOI 10.1007/s10096-011-1369-9
(Fig. 1). When a direct current is applied (A), electrochem-
ical processes at the material electrode surface transform the
electrolyte (NaCl) into an activated metastablestate,
exhibiting elevated chemical reactivity and resulting in the
modification of molecular ionic structures [11]. Titanium
(Ti) electrodes coated with porous layers of a metal oxide
catalyst (e.g. RuO
2
,TiO
2
, SnO
2
, IrO
2
)[15] are used due to
improved characteristics of stability, selectivity, electro-
chemical reactivity, corrosion resistance and operating life
of electrodes [1618]. In the anodic chamber (Fig. 1), the
continuously perfused salt (NaCl) solution reacts at the
anode surface, producing mainly chlorine and oxygen, but
also other reactive oxidants which are released into the bulk
fluid. This is dependent on the redox reactions of strongly
adsorbed electro-active water-derived intermediate molecu-
lar species [1922], and a large scientific body of evidence
now exists for these processes [15,16,23,24]. This
reaction is pH-dependent and (according to the Nernst
equation) dictates which free form of chlorine is most
prevalent within generated solution; Cl
2
, HClO or ClO [25,
26]. The exact physicochemical properties of the resulting
anolyte (ECAS
a
) is dependent on both the characteristics of
the electrochemical cell and its operating parameters,
although conditions conducive to a low pH (23) and
high oxidation-reduction potential (ORP) (above +800 mV)
are usually sought. In the cathodic chamber (Fig. 1),
hydrogen is generated, along with other reactive substances
(largely antioxidants), resulting in a decrease in the redox
potential and an increased pH. Although these cathodic
solutions (ECAS
c
) have been used for the effective
treatment of industrial effluents [15], they possess only
limited antimicrobial activity [27,28], and, hence, will not
be the focus of this review.
The transformation of the electrolyte into a metastable
state is not permanent. Upon the generation and recovery of
ECAS
a
, the chemical species present will shift spontane-
ously from this thermodynamically un-equilibrated condi-
tion to a stable non-active form, during what is known as
the period of relaxation[29]. The rate of relaxation, and,
thus, the half-life of the active solution, is ECAS
a
-specific
[30]. However, the stability of ECAS
a
can be improved by
increasing the pH, since this shifts the chemical equilibrium
towards non-volatile chlorine species; this has been shown
experimentally [10,31]. In contrast to the significant
reductions in residual free chlorine, studies have shown
that the pH, ORP, conductivity and chloride ion concentra-
tion levels are all relatively stable during short-term storage
[31,32], indicating that the oxidising potential of these
solutions is largely retained.
Identification of the active antimicrobial agents
within ECAS
a
ECAS
a
characteristically have an ORP of +800 mV to
+1,200 mV, creating an environment outside the working
range of important microbial processes [33], including
energy-generating mechanisms [34]. If immersed in these
solutions, microorganisms will be exposed to powerful
oxidants which will sequester electrons with high efficiency
from microbial structural compounds, causing the rupturing
of biochemical bonds and subsequent loss of function.
Moreover, the high ORP environment is thought to create
an unbalanced osmolarity between the ion concentrations in
the solution and that within unicellular organisms, further
damaging membrane structures [35]. This will cause
increased membrane porosity, enabling oxidising moieties
(present in excess in ECAS
a
) to penetrate (via diffusion) into
the cell cytoplasm, ultimately leading to the inactivation of
intracellular protein, lipids and nucleic acid, rendering the
cell non-functional.
It has been stated that ORP is more important than free
chlorine content in terms of predicting the disinfectant
potential of a given ECAS
a
[36,37], and this has been
demonstrated experimentally by a number of researchers
[38,39]. The ORP of ECAS
a
has been found to be
inversely proportional to the pH [37], and that decreasing
the pH increases the antimicrobial potential of ECAS
a
, even
if the residual chlorine levels are kept constant [40]. At low
pH levels (pH 25), HOCl will be the predominant
Fig. 1 Prototypical electrochemical cell used for generating electro-
chemically activated solutions (ECAS), comprising of two electrodes,
an anode (1) and a cathode (2), separated by an ion-permeable
exchange diaphragm (3). During operation, a salt solution is
continuously perfused into both the anodic and cathodic chambers.
The main general chemical reactions thought to occur at each
electrode when a unipolar direct current is applied (amperage; A) are
shown, with additional chemical transformations being dependent on
the nature of the electrode material and specific electrolyte used
Eur J Clin Microbiol Infect Dis
chlorine species present, leading many researchers to
conclude that HOCl is the primary active agent present in
acidic ECAS
a
[10,30,40], being known to disrupt
microbial structure [1] and the general cellular activity of
proteins [2,41,42]. In addition, hydroxyl radicals (the
strongest oxidising agent characterised) have also been
detected within ECAS
a
[15,4346], and it is likely that a
combination of active moieties contribute to the antimicro-
bial efficacy of ECAS
a
, creating an antimicrobial milieu
that has been likened to that utilised by phagosomes to
induce killing within phagocytic cells of the mammalian
immune system [47].
The antimicrobial efficacy of ECAS
a
is thought to be at
least partially dependent on non-specific, short-lived,
highly reactive oxidative moieties. These components will
react with any organic compounds present within the
environment, whether this is the desired target or not. In
fact, the presence of organic loading has been shown to
significantly reduce the antimicrobial potential of ECAS
a
[4850]. This is an important consideration in their
application, since where a high organic load is likely, a
high-strength solution (high ORP) or continual delivery
will be required to maintain a high level of disinfection
potential.
Efficacy of ECAS
a
against specific microbial targets
The susceptibility assays used by different research groups
to assess the antimicrobial efficacy of ECAS
a
often vary,
making direct comparisons problematic. However, if the
quantitative studies within the literature are taken together,
it is clear that ECAS
a
is active against a broad spectrum of
microorganisms (see Table 1), and these are described and
discussed below.
Bacteria
Table 1lists the aerobic, facultative and anaerobic bacterial
species that have been shown to be susceptible to ECAS
a
treatment during in vitro suspension tests. Extensive ECAS
biocidal research has also been performed within Russia,
Japan and China, although Table 1only accounts for those
studies published in English language journals. The kill rate
(k) values for the various ECAS
a
have been calculated
using the viable count and time data points provided within
each experimental study in order to account for the various
experimental protocols (in particular, exposure time), since
the kill rate is the key comparator for different biocidal
experimental parameters [73]. However, within most
studies, only a single contact and recovery time point was
used. This is likely to account for the wide variation in kill
rates observed, since, if only a single time point is taken
after a long incubation time, an apparently slower kill rate
will be recorded, even if the majority of the killing occurred
in the first few seconds of exposure. Very few studies have
extensively characterised the antimicrobial kinetics of
ECAS
a
, and further research is required in this area.
Nonetheless, the data is still representative of the spectrum
of bactericidal activity of both acidic (pH 25) and neutral
(pH 58) ECAS
a
. It is clear that acidic ECAS
a
has a broad
spectrum of activity, including clinically relevant strains
after only short exposure times (high kill rate), comparable
to other regularly used disinfectants, including sodium
hypochlorite, chlorhexidine gluconate, glutaraldehyde and
benzalkonium chloride [74,75]. The exact chemical
composition of ECAS
a
can vary, but one study comparing
the antimicrobial activity of various commercial acidic
ECAS
a
solutions generated using either pure(reverse-
osmosed) or localtap water showed no differences in
activity [51]. More recently, there has been increased
interest in pH-neutralised ECAS
a
as an antimicrobial (e.g.
Steriloxand Microcyn), and although previous studies
have shown antimicrobial efficacy to be a function of pH
[30,31,40], these solutions have also shown broad-
spectrum bactericidal activity [61,62,76](Table1).
Neutralised ECAS
a
are thought to benefit from increased
biocompatibility and longer shelf life [76] and, hence, they
may be more commercially valuable, having been proven to
retain significant antimicrobial activity. However, few direct
comparisons of acidic and pH-neutralised ECAS
a
have
been made (in particular, shelf life), precluding any
meaningful conclusions, and further research is required
to determine the effect of altering the pH alone on
antimicrobial efficacy.
The high lipid content outer membrane and cell
membrane bacterial structures are likely to be the primary
ECAS
a
target. ECAS
a
are thought to sequester electrons
from these structures, rendering them unstable, potentially
allowing oxidants to penetrate into the cell cytoplasm,
causing widespread oxidation and the inactivation of
essential cellular processes [76]. Low pH could also
sensitise the outer membrane of Gram-negative bacterial
cells, enabling more efficient entry of hypochlorous acid
[1]. It has been postulated that the high ORP of ECAS
a
interferes with the cellular redox signalling pathways (e.g.
glutathione disulphideglutathione couple), causing cell
permeabilisation, oxidative intra-cellular formation of
disulphide bridges, consequent changes in protein structure
and function, and, ultimately, cell lysis [39]. The effect of
ECAS
a
on bacterial cells has been directly observed using
transmission electron microscopy [60,66], atomic force
microscopy [39,77] and fluorescence microscopy [39],
providing evidence of the direct effects on the bacterial cell
envelope. Once within the bacterial cell, ECAS
a
has been
shown to cause the total destruction of chromosomal and
Eur J Clin Microbiol Infect Dis
Table 1 Range of experimental kill rates determined for acidic (pH 2
5) and neutralised (pH 58) electrochemically activated solution
anolyte (ECAS
a
) against aerobic, facultative and anaerobic bacterial
target species, bacterial spores, and eukaryotic cells, within in vitro
suspension tests. Kill rates (k) are expressed as log
10
colony-forming
units (CFU) ml
1
reduction per minute from the viable count and time
data points provided within the literature, and, therefore, must be
taken as the lowest estimates. Qualitative studies are reported where
no quantitative data exist in the literature
Target organism Experimental kill rates (k) of various ECAS
a
(log
10
CFU ml
1
reduction per minute)
Acidic ECAS
a
Neutralised ECAS
a
Aerobic/facultative bacteria
Acinetobacter spp. + [51] 10.0 [52]
Actinobacillus actinomycetemcomitans +[53]+[53]
Aeromonas liquefaciens 13.8 [54]
Alcaligenes faecalis 13.6 [54]
Bacillus subtilis +[10] 1.7 [55]
Bacillus cereus 2.35.9 [30,54,56]
Burkholderia cepacia 34.5 [57]
Citrobacter freundii 13.3 [54]
Campylobacter jejuni 44.9 [58]
Escherichia coli 1.437.4 [36,38,40,54,56,57,59,60] 1.716.0 [48,52,59,61]
Enterobacter aerogenes 16.0 [58] 10.0 [52]
Enterococcus spp. 14.5 [54] 3.515.4 [48,52,62]
VRE 3.510.0 [52,62]
Flavobacter spp. 14.2 [54]
Haemophilus influenzae >10.0 [52]
Helicobacter pylori +[63] 3.50 [62]
Lactobacillus spp. 4.45.0 [55]
Legionella pneumophila 8.0 [64]
Listeria monocytogenes 1.316.3 [36,40,56,65]
Klebsiella spp. 10.0 [52]
Micrococcus luteus 10.0 [52]
Mycobacterium spp. + [66,67] 3.55.1 [57,63]
Proteus spp. 14.0 [54] 10.0 [52]
Pseudomonas aeruginosa 14.137.4 [54,57,68] 8.016.0 [48,52,64]
Salmonella spp. 6.18.0 [59,69] 5.216.0 [59,61,65]
Serratia marcescens 37.4 [57] 10.0 [52]
Staphylococcus spp. 3.737.4 [54,57,59,60,69] 3.916.0 [55,59,61,64,69]
MRSA 28.837.4 [57,68] 13.4 [48]
MRSE 3.2 [55]
Streptococcus spp. + [51,53] 3.85.0 [55]
Xanthomonas maltophilia +[51]
Anaerobic bacteria
Actinomyces spp. + [53] 2.9 [55]
Bifidobacterium bifidum 5.0 [55]
Bacteroides fragilis 10.0 [52]
Eubacterium lentum 3.0 [55]
Fusobacterium nucleatum +[53] 2.9 [55]
Peptococcus niger 4.2 [55]
Peptostreptococcus anaerobius 4.1 [55]
Prevotella melaninogenica +[53] 5.8 [55]
Porphyromonas spp. + [53] 3.5 [55]
Prevotella loeschii +[53] 5.5 [55]
Propionibacterium acnes 4.6 [55]
Veillonella parvula 4.7 [55]
Eur J Clin Microbiol Infect Dis
plasmid DNA, RNA and proteins when analysed using both
sodium dodecyl sulphate polyacrylamide gel electrophoresis
(SDS-PAGE) [60,78,79] and a restriction fragment length
polymorphism pattern (RFLP) assay [66]. However, it is
likely that cell death/lysis results from the early events
involved with cell membrane disruption and consequent
potassium leakage from the cell.
Bacterial spores
Bacterial spores are innately more resistant to antimicrobial
treatment due to various physiological factors [80,81].
ECAS
a
(in common with all known biocides) have shown
reduced efficacy against spores compared to vegetative
cells, although it is evident from the literature that
significant sporicidal activity has still been proven in vitro
for both acidic and neutralised ECAS
a
(see Table 1). One
study using acidic ECAS
a
in conjunction with a kinetic
assay showed spores of Bacillus atrophaeus to be signifi-
cantly more resistant than Clostridium difficile, although
both test strains were reduced to minimum detection levels
within 90 s of exposure [68]. pH-neutralised ECAS
a
have
been found to have greater sporicidal activity than some
existing biocides, e.g. glutaraldehyde [51], 70% ethanol or
70% isopropanol [61]. Moreover, a pH-neutralised ECAS
a
was found to have a significant sporicidal activity against
the potential bio-terrorism agent Bacillus anthracis, equiv-
alent to that of 5% calcium hypochlorite advocated by the
U.S. military for the decontamination of spores on skin or
surfaces [82]. The authors concluded that, due to the toxic
and corrosive nature that existing agents posed to human
health, pH-neutralised ECAS
a
may offer a real practical
alternative.
One study using Bacillus subtilis knock-out mutant spores
showed that ECAS
a
was not targeting DNA or germination as
its primary mechanism of action, as evidenced by the
observation of germination-specific events even in killed
spores [71]. It was postulated that ECAS
a
oxidatively
modifies the inner membrane, targeting proteins and unsatu-
rated fatty acids, and that, since this membrane structure will
eventually become the outgrowing sporescell membrane,
this ultimately renders the spore non-functional [71].
Biofilms
Microorganisms are now known to form resistant biofilm
structures [83,84], which are thought to have evolved as a
tenacious survival strategy [85]. Although these structural
communities are undoubtedly ubiquitous in nature, few
experimental studies have been performed to specifically
investigate the sensitivity of these antimicrobial-tolerant
communities to ECAS
a
. The effective removal of mature
Pseudomonas aeruginosa biofilms from the surface of glass
and stainless steel after treatment with either acidic or
neutralised ECAS
a
has been shown in vitro by light and
electron microscopy [86]. In addition, removal of the
extracellular matrix of both Escherichia coli and sulphate-
reducing bacterial biofilms has been observed using atomic
force microscopy in vitro, after treatment with acidic ECAS
a
[77], indicating its possible application as an antibiofouling
agent. Listeria monocytogenes biofilms, formed on the surface
of stainless steel coupons, were also shown to be sensitive to a
Table 1 (continued)
Target organism Experimental kill rates (k) of various ECAS
a
(log
10
CFUml
1
reduction per minute)
Bacterial spores
Bacillus anthracis 0.2 [70]
Bacillus atrophaeus 3.7 [68] 0.42.0 [52,61]
Bacillus cereus 1.326.98 [54,56]
Bacillus subtilis 0.9 [66] 1.015.0 [48,71]
Clostridium difficile 16.3 [68] 2.0 [62]
Clostridium perfringens 0.04 [72]
Streptomyces spp. + [28]+[28]
Eukaryotes
Aspergillus spp. 1.48 [46] 5.25 [46]
Candida spp. 3.5 [62] 3.516.0 [48,61,62,64]
Cryptosporidium parvum oocysts * [72]
Various environmental fungi + [70]
VRE: vancomycin-resistant Enterococcus; MRSA: methicillin-resistant Staphylococcus aureus; MRSE: methicillin-resistant Staphylococcus
epidermidis
+Qualitative study only
*1.3 log reduction of oocyst infectivity in 1 h
Eur J Clin Microbiol Infect Dis
neutralised ECAS
a
, which elicited a 9 log
10
reduction after
5 min of treatment [86]. Numerous other studies have looked
at the inactivation of surface-associated bacterial cells
subsequent to ECAS
a
treatment, and have shown significant
activity against Staphylococcus aureus (including methicillin-
resistant S. aureus [MRSA]), Enterococcus faecalis,E. coli,L.
monocytogenes,Acinetobacter baumannii,Helicobacter
pylori and Mycobacterium spp. [7,27,63,69,87]. Biofilms
are of particular concern in the oral cavity, as these polymicro-
bial communities can contribute to periodontal disease states
and ECAS
a
have been shown to be effective at removing
necrotic dentine and pulp tissue, as well as microorganisms
from tooth surfaces [88], which would otherwise likely lead to
biofilm development associated with oral diseases.
The antimicrobial activity of ECAS
a
is dependent on
highly reactive non-specific oxidants (as previously de-
scribed), and these active moieties are almost certainly
competitively quenched by the high levels of organic load
present within a biofilm structure (particularly the extracel-
lular polymeric matrix). Therefore, a sufficient concentration
and exposure time would be required to reach cells deeper
within the biofilm architecture. In fact, one author postulated
that hydroxyl radicals present in ECAS
a
may cause the
collapse of the highly structured hydrated biofilm matrix by
removing hydrogen ions (through oxidation), exposing
deeper biofilm cells to antimicrobial agents [89]. Collectively,
the literature supports the potential use of ECAS
a
against
biofilms structures, but further research is required in this
area to elucidate the kinetics and characterise appropriate
treatment regimens.
Eukaryotes
ECAS
a
is a broad-spectrum, non-selective biocide, hence, it
has been shown to effectively inactivate certain pathogenic
eukaryotic species (see Table 1) and is thought to damage
cellular functional structures [46]. Of particular note is its
efficacy against Cryptosporidium parvum, a waterborne
pathogen that has previously been shown to be resistant to
standard chlorine treatment [90]. pH-neutralised ECAS
a
showed significant activity against C. parvum oocysts in
contrast to little or no activity using a free chlorine solution
[72]. Although few eukaryotic pathogens have been tested
for their sensitivity to ECAS
a
(see Table 1), it is evident
from a study using environmental fungal species that it has
significant broad-spectrum antifungal potential [70]. The
sensitivity of eukaryotic cells to ECAS
a
raises concerns
regarding mammalian toxicity, which is considered later.
Microbial toxins
The ability of ECAS to inactivate pre-formed bacterial
toxins has been investigated using staphylococcal
enterotoxin-A (SEA) [91]. This toxin is classically heat-
stable and resistant to treatment with strong acid and alkali;
nonetheless, significant inactivation was recorded when
ECAS
a
was present in excess [91]. In-depth analysis found
that the immunoreactive site of SEA was denatured (even in
the presence of organic loading) and that extensive peptide
fragmentation occurred with accompanying loss of amino
acid content [91]. The ability of ECAS
a
to inactivate fungal
toxins has been investigated using the aflatoxin of
Aspergillus parasiticus and a significant reduction in the
mutagenic potential of this aflatoxin was measured using a
conventional Ames test [44]. The mode of action was
postulated to be mediated by free-radical reactions, since
the presence of radical scavengers (mannitol and thiourea)
significantly reduced the efficacy of ECAS
a
in destroying
aflatoxin [44]. These isolated reports of the ability of
ECAS
a
to inactivate microbial toxins indicate its efficacy
not only at killing whole microorganisms, but also
deactivating or degrading their virulence factors.
Viruses
Chemical disinfection is seen as a valuable tool in limiting
the environmental spread of infectious virions. Numerous
studies have demonstrated the virucidal activity of ECAS
a
against a broad range of targets [48,51,61,9297],
comparable to that of other biocidal agents [92]. Most
methodologies expose virus particles in suspension to
ECAS
a
in the presence/absence of organic loading, where-
by ECAS
a
reduces the number of viable virus particles as
measured by cytopathic effects of the target virions in
subsequently infected cell lines [48,51]. An immunoassay
has been used to assess ECAS
a
-treated hepatitis B virus
(HBV) surface antigen (in the absence of an appropriate
whole-cell bioassay) and a significant concentration-
dependent reduction in the measured antigenicity was
observed [93]. The authors postulated that this was
indicative of a reduction in the infectivity of human HBV
[93] and this is supported by the finding that ECAS
a
reduced the infectivity of a hepatitis B surrogate, duck
hepatitis B virus, indicating the efficacy of ECAS
a
against
hepadnaviruses [92]. Similarly, the ECAS
a
treatment of the
norovirus surrogate bacteriophage MS2 was shown to
significantly reduce infectivity, although significantly lon-
ger exposure times were required for surface-associated
virions, presumably due to reduced accessibility of the
active moieties [94]. It was, therefore, suggested that
carrier/surface tests are more appropriate when testing the
virucidal activity of environmental biocides. Fogged
ECAS
a
has been found to significantly reduce the surface
levels of both human norovirus and surrogate viruses, as
detected by reverse transcriptase polymerase chain reaction
[94], and both acidic and neutralised ECAS
a
have shown
Eur J Clin Microbiol Infect Dis
significant activity against human immunodeficiency virus
(HIV), even when infectious particles are pre-adsorbed onto
an inanimate surface [61,95]. Since viruses do not have
cell walls, it has been postulated that the mode of action is
likely to be the inactivation of surface protein, destruction
of the viral envelope, inactivation of viral enzymes or the
destruction of viral nucleic acid [92,93], collectively
eradicating their potential infectivity. In support of this
theory, at least some ECAS
a
components have been shown
to penetrate the viral envelope [93].
Potential toxicity
The goal of disinfection is to reduce potentially pathogenic
microbial populations to safe levels. In the clinical
environment where contact with humans is either likely
(e.g. cleaning products) or inevitable (e.g. topical treat-
ments), agents must not be hazardous or toxic to living
tissue, according to their particular application and in-use
concentrations. A large scientific body of evidence now
exists indicating the safety and non-toxicity of ECAS
a
[11].
A single-dose and 28-day repeated dose oral toxicity study
of ECAS
a
in rats found no evidence of adverse effects [98],
and mice given free access to ECAS
a
as drinking water for
8 weeks showed no toxic side effects [99]. Moreover, no
toxicity has been observed using in-use concentrations
during acute oral toxicity tests (LD
50
) upon application to
mucous membranes, in accumulation irritation tests or in
sensitisation tests, indicating its biocompatibility [52,92,
93,100102]. In fact, the observed biocompatibility of
ECAS
a
has often been determined at relatively high
exposure levels, in comparison with the anticipated low
levels that would be used in the real clinical situation [103].
The incubation of ECAS
a
with human cell lines in vitro has
shown more mixed results, where some studies have shown
no effect [102,104], while others have shown significant
cytotoxicity [105107], although usually to a lesser degree
than other commonly used biocides [104106]. However, in
vitro cytotoxicity is not always indicative of toxicity when
used in vivo, as has been observed previously [105]. In
vitro mutagenicity studies have failed to find any evidence
of ECAS
a
induced genotoxicity, using either the Ames test
[102] or the genotoxicity micronucleus test [52], indicating
its safe usage. Moreover, a recent wide-ranging toxicity
study on a neutralised ECAS
a
found that it did not degrade
nucleic acids or induce oxidative damage in dermal
fibroblasts in vitro [47]. This study led the authors to
conclude that ECAS
a
did not target cell nuclei, produced
only limited damage to cell membranes and did not induce
DNA oxidation or accelerated ageing [47]. It is also worth
noting that ECAS
a
presents no environmental hazard, since
it slowly reverts to salt water during the period of chemical
relaxation, and is effectively inactivated by organic matter
when present in trace amounts.
Potential corrosiveness of ECAS
The potential for biocides to cause material corrosion must
be investigated before being widely used to disinfect
inanimate surfaces. ECAS
a
have highly oxidative proper-
ties, hence, this is of particular concern if ECAS
a
are to be
used as broad-spectrum multipurpose disinfectants. Few
scientific studies have been performed to specifically
investigate this, although one study has shown that low-
level metal corrosion (stainless steel) and synthetic resin
degradationoccurredduringa36-dayincubationwith
various acidic ECAS
a
(replenished daily) [51]. This was
described as surface corrosion undetectable to the naked
eyein comparison to the strong corrosion exhibited by a
0.1% sodium hypochlorite solution also tested as a
comparison over the same 36-day exposure time. It was
concluded that these experimental results, coupled with
their observations of the use of ECAS
a
within a clinical
setting for >3 years (with no observed corrosion problems),
demonstrated a low risk of ECAS
a
-mediated corrosion. A
more recent study has shown that acidic ECAS
a
had no
adverse effect on stainless steel surfaces (after 8 days of
contact), but significant corrosion was seen for carbon steel
and, to a lesser extent, on copper and aluminium surfaces
[108], likely to be due to the known susceptibility of these
materials to oxidising agents (particularly chloride ions).
Interestingly, this study showed how corrosion could be
limited by using neutralised ECAS
a
[108], highlighting the
importance of testing the corrosive nature of specific
ECAS
a
within the real-world situation where they are to
be applied.
Antimicrobial applications in healthcare: evidence
of efficacy
Although initially used in an empirical manner, a large
scientific body of evidence now exists from investigating
the comparable merits of using ECAS
a
against the best
available treatmentwithin various medical disciplines:
(i) Treatment and prevention of wound infection
The use of targeted antibiotic therapy is essential in
wound care for the treatment of known wound infections
(e.g. S. aureus), but, due to the rise of antimicrobial
resistance, the general use of broad-spectrum antibiotics
is being restricted. Therefore, although prophylactic
antibiotics are still used in surgery, broad-spectrum
biocides are finding increased usage in antiseptic scrubs,
Eur J Clin Microbiol Infect Dis
as wound irrigants, as well as for incorporation into
wound-dressing products. Acidic ECAS
a
used twice-
daily to wash infectious defects or ulcers (15 case study
participants) was shown to reduce bacterial infections
and aid debridement, often where traditional treatment
was found to be ineffective [109]. In another case study-
based trial, seven patients with peritonitis or intraperi-
toneal abscesses underwent twice-daily ECAS
a
lavage
procedures, and were found to revert to a microbial-
negative state within 37days[33]. ECAS
a
treatment
significantly improved the survival rates within a rodent
in vivo burn wound model infected with P.aeruginosa,
along with a reduction in serum endotoxin levels [110].
Moreover, acidic ECAS
a
have been found to promote
re-epithelisation (in an in vivo burn wound model),
increasing the proliferation of lymphocytes and macro-
phages associated with dense collagen deposition [111].
The clinical evidence for the use of ECAS
a
is largely
based on small-scale case studies, but it has shown
promise in reducing bacterial infections in burn wounds
[112], for the treatment of refractory chronic ulcers
[109], as well as synergistic necrotising infections [113],
and a neutralised ECAS is now commercially available
specifically for the treatment of wounds (Dermacyn,
Oculus Innovative Sciences, Petaluma, CA, USA [114]).
Neutral ECAS
a
have been shown to significantly
increase healing rates and reduce pain levels in
recalcitrant venous leg ulcers [115,116], improve
healing outcomes in diabetic foot ulcers [47,117,118],
shown potential applications in advanced wound care in
combination with negative pressure therapy [119]and
have been shown to be more effective than povidone
iodine in treating diabetic foot ulcers [120]. Moreover, a
recent randomised controlled trial using a daily instilla-
tion of pH-neutralised ECAS
a
within wound dressings
for the management of wide postsurgical lesions of the
diabetic foot found it to significantly improve healing
rates, while significantly reducing the bacterial load
(compared to the control treatment, povidoneiodine)
with no reported adverse effects [121].
ECAS
a
is thought to help promote healing by
reducing the bacterial load, enhancing local blood
supply, accelerating neovascularisation, reducing inflam-
mation and producing an environment hostile to
opportunistic pathogens [117 ]. In addition, it is also
thought to reduce odour levels by reacting with
putrefacting necrotic tissue [47]. ECAS
a
have been
trialled as a preventative therapeutic solution for
postoperative infection [122] and reductions in the rates
of infection (including those attributable to MRSA) have
been observed [123]. ECAS
a
have also shown potential
for use in disinfecting the ocular surface [105] and the
treatment of inflammatory acne lesions [124], providing
further evidence of their anti-inflammatory activity.
Collectively, ECAS
a
have shown promise in providing
effective infection control with minimal damage to the
regenerating host tissue. However, due to the predom-
inately small-scale case study-based nature of the trials
conducted, the evidence must be viewed with caution,
and large-scale trials will be required before wide-spread
usage is likely to be accepted.
(ii) Treatment and prevention of periodontal disease
The dental community has long sought adequate
antimicrobial products to try to control proliferation of
the indigenous oral microflora, particularly during
dental surgery when the barrier functions of the host
are often compromised. Early studies have shown that
ECAS
a
is capable of removing the smear layer from
root canals in vivo [88] and was as effective as
chlorhexidine in inhibiting plaque formation in human
subjects [125]. This confirmed that the in vitro activity
of ECAS
a
against oral microorganisms (see Table 1)
was also observed in vivo, whereby acidic, neutralised
and low available chlorine concentration ECAS
a
have
all been shown to be active against cariogenic bacteria
[53]. A tooth irrigant should not only possess
antimicrobial activity, but also provide mechanical
flushing action and dissolve remnants of organic
tissue, ideally without damaging surrounding healthy
tissue. One pilot study using extracted teeth showed
that the combined application of ECAS
a
and ECAS
c
could be used as an effective root canal cleaning
solution, comparable to sodium hypochlorite, as
visualised by ESEM [126]. However, the antimicrobial
efficacy of ECAS
a
compared to the best available
treatmenthas been questioned by some authors, who
have shown it to have only limited activity compared
to other in-use treatments, e.g. EDTA or NaOCl [27,
127,128]. The discrepancies in the literature are likely
due to the method of delivery, and this has been
suggested to be the critical treatment factor [128,129].
(iii) Medical device disinfection
One of the earliest clinical applications of ECAS
a
was for disinfecting medical equipment, and there are
many studies showing its efficacy at disinfecting
endoscopy equipment [48,62,63,102], including
bronchoscopes [7] and haemodialysis equipment [51].
However, due to the low levels of corrosion associ-
ated with ECAS
a
use (see the section titled Potential
Corrosiveness of ECAS), one UK endoscope manu-
facturer has stated that its warranty is void if ECAS
a
is used to disinfect them [130]. Interestingly, one
study showed clinical bacterial isolates to be more
resistant than laboratorystrains to ECAS
a
treatment
[48], highlighting the need to include targets relevant
to the in-use application of this technology during
Eur J Clin Microbiol Infect Dis
research and development. One concern in dental
environments is the microbial contamination of dental
unit water lines, which, if inadequately disinfected,
may harbour polymicrobial biofilms containing po-
tentially pathogenic organisms. Since ECAS
a
have
been shown to be effective at removing biofilms, it is
perhaps not surprising that they have proven to be
useful in reducing the bacterial load of these medical
devices [89,131]. The fast-acting nature of these
disinfectants reduces required contact and exposure
times, potentially enabling high-throughput disinfec-
tion of medicinal equipment, often an important
factor for repeat-use medical apparatus.
(iv) Environmental decontamination
Potentially pathogenic microorganisms can persist
within the healthcare environment not only via direct
transmission from patient to patient, but also through
survival on the diverse array of inanimate surfaces
present. Although viruses may only persist for short
periods, bacteria can survive for months using the low-
level nutrient sources available [132] or can revert to a
dormant state (e.g. spores) until they are exposed to
conditions conducive to growth. The potential use of
ECAS
a
to disinfect inanimate surfaces has been shown
experimentally [69], and fogged ECAS
a
has shown
activity against MRSA, Acinetobacter baumannii and
norovirus [94,133]. This could have relevant applica-
tions in decontaminating large spaces (e.g. hospital
wards), and targeted use of fogged/aerosolised ECAS
a
may help control healthcare-associated infection out-
breaks. A neutralised ECAS
a
has been shown to be
effective at reducing bacterial levels in industrial
cooling towers in accordance with the UK Health and
Safety Commission (HSC) Approved Code of Practice
andGuidance(ACOP)[134]. Since severalhospital
outbreaks of Legionella pneumophila are thought to
have originated from contaminated cooling towers
[135], this demonstrates the wide range of applications
where ECAS
a
may help to control the microbial
bioburden within global healthcare environments.
Interestingly, ECAS
a
have also been investigated for
their application in hand washing, but, although
showing significant reductions in bacterial numbers
compared to washing in water, have shown only
limited activity when compared to existing agents
[136139].
Discussion
The introduction of the Biocidal Product Directive 98/8/EC,
and subsequent ongoing 10-year review of all existing and
emerging biocidal agents, has significantly reduced the
number of biocide products available on the European
market (as well as limiting the introduction of new or novel
agents), largely due to the prohibitive costs involved with
gaining approval [140]. Therefore, it is imperative that
medical, government, industrial and academic institutions
collaborate in order to help develop or validate the use of
novel biocidal products in maintaining effective bioburden
control, especially within the healthcare environment. The
advantages and disadvantages of ECAS
a
as applied to its
potential usage within a healthcare setting are listed in
Table 2. Although there is an initial expenditure on the
electrolytic cell, once installed, the production of active
solutions is cheap due to the relative abundance of raw
materials (H
2
O and NaCl). Due to on-site generation and
low operator skill requirements, high ECAS
a
production
rates can be achieved, and this negates the need for the
transport or storage of biocidal chemicals. The broad-
spectrum antimicrobial activity of ECAS
a
enables high-
level disinfection as defined by the Centers for Disease
Control and Prevention (CDC) [141], and their favourable
biocompatibility means that ECAS
a
are ideally suited as
both an environmental decontaminant and in the control or
treatment of skin surface or mucous membrane infections.
ECAS
a
do have their limitations. In general, they cannot be
stored for long periods and the potency of ECAS
a
will be
dependent on the efficiency of the generator cell. In
addition, acidic ECAS solutions can cause low levels of
corrosion to some materials [108], and its antimicrobial
activity quickly diminishes on contact with organic sub-
strates [49]. Therefore, it is important that, for every new
application, the actual ECAS
a
disinfection or treatment
regimen is appropriately designed and supported by a
scientific body of evidence to validate its usage. For
example, for effective disinfection in the presence of high
Table 2 General advantages and disadvantages of ECAS
a
as applied
to its potential usage within a healthcare setting
Advantages Disadvantages
Broad-spectrum antimicrobial
activity
Initial expenditure on generator
Rapid disinfection time Generator servicing and
maintenance
Inexpensive Limited shelf life
Easily accessible raw materials Inactivated by organic loading
On-site or in-situ generation Acidic ECAS
a
can be corrosive
Requires little operator skill
Limited toxicity
Environmentally compatible
Evidence of being
anti-inflammatory
Eur J Clin Microbiol Infect Dis
organic loads, repeated or continual delivery of ECAS may
be required. However, characteristics undesirable for one
application may be advantageous in another, and the
organic quenching of ECAS
a
activity is likely to underpin
its low toxicity, thereby, promoting its usage as a skin and
mucous membrane antiseptic.
The effective use of disinfectants within the healthcare
environment almost certainly provides widespread protection
to both healthcare practitioners and patients against possible
contamination with potentially pathogenic organisms. More-
over, with the concern over antibiotic-resistant nosocomial
infections, new or novel broad-spectrum antimicrobial treat-
ments are in high demand. ECAS have been studied for many
years and have been found to be highly efficacious biocidal
agents, with increasing reports of their effectiveness in real-
world applications; however, they are still not in widespread
use, particularly within the healthcare environment. The
paucity of wide-ranging clinical trials is likely to be a
contributing factor, but recent guidelines do recognise the
potential of ECAS
a
for disinfection and sterilisation in
healthcare facilities [141]. Further application-focussed re-
search and development is required if ECAS are to replace
established methods of disinfection and antisepsis, and find
common usage within healthcare environments.
Acknowledgements The authors would like to thank Dann Turner
for his critical assessment of the manuscript.
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... The use of conventional chlorine-based disinfectants, such as hypochlorite (OCl -), within POU water disinfection requires the storage and transportation of hazardous chemicals and can also cause the formation of harmful DBPs and the deterioration of taste and odour 11 . Ultraviolet and ozone are well established as disinfection technologies within both decentralised/POU 12,13 and large scale drinking water treatment 14,15 , but an added benefit of implementing electrochemcially activated solutions [ECAS] is it has capability to be used externally to water treatment systems as part of food production 16,17 or in healthcare settings 18,19 . A limited number of studies have compared ECAS against commonly used chlorine agents for decentralised disinfection applications 20,21 . ...
... Electrochemical disinfection technologies are emerging within the water sector 8,22 , and are currently well established in the food sector 16,17 , and to a lesser extent, in clinical/healthcare settings 18,19 . The generation of ECAS has previously been described in detail 19 and are generated by passing a saline solution through an electrochemical cell with separate anodic and cathodic compartments. ...
... Electrochemical disinfection technologies are emerging within the water sector 8,22 , and are currently well established in the food sector 16,17 , and to a lesser extent, in clinical/healthcare settings 18,19 . The generation of ECAS has previously been described in detail 19 and are generated by passing a saline solution through an electrochemical cell with separate anodic and cathodic compartments. Anodic solutions are highly oxidative with oxidation-reduction potential [ORP] values greater than +1000 mV 23,24 . ...
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Chlorine solutions are used extensively for the production of biologically safe drinking water. The capability of point-of-use [POU] drinking water treatment systems has gained interest in locations where centralised treatment systems and distribution networks are not practical. This study investigated the antimicrobial and anti-biofilm activity of three chlorine-based disinfectants (hypochlorite ions [OCl-], hypochlorous acid [HOCl] and electrochemically activated solutions [ECAS]) for use in POU drinking water applications. The relative antimicrobial activity was compared within bactericidal suspension assays (BS EN 1040 and BS EN 1276) using Escherichia coli. The anti-biofilm activity was compared utilising established sessile Pseudomonas aeruginosa within a Centre for Disease Control [CDC] biofilm reactor. HOCl exhibited the greatest antimicrobial activity against planktonic E. coli at >50 mg L−1 free chlorine, in the presence of organic loading (bovine serum albumen). However, ECAS exhibited significantly greater anti-biofilm activity compared to OCl- and HOCl against P. aeruginosa biofilms at ≥50 mg L−1 free chlorine. Based on this evidence disinfectants where HOCl is the dominant chlorine species (HOCl and ECAS) would be appropriate alternative chlorine-based disinfectants for POU drinking water applications.
... The well-known limitations of sodium hypochlorite have encouraged interest in alternative disinfectants for use in hospitals, and in particular the use of locally-sourced disinfectants to avoid issues with product degradation. One alternative disinfectant can be produced locally by saline electrolysis [5,6]; hence, these products may be termed electrolysed water. The active ingredients resulting from electrolysis include chlorine, hypochlorous acid and hypochlorite ions or a combination of these. ...
... Aqueous hypochlorous acid is emerging as a potent and environmentally safe disinfectant available. This compound, in appropriate concentrations, can rapidly inhibit or kill a wide range of human pathogens [6], including bacteria and spores, viruses such as the SARS-CoV-2 coronavirus [10,11], fungi, protozoa and mycobacteria [6,12]. ...
... Aqueous hypochlorous acid is emerging as a potent and environmentally safe disinfectant available. This compound, in appropriate concentrations, can rapidly inhibit or kill a wide range of human pathogens [6], including bacteria and spores, viruses such as the SARS-CoV-2 coronavirus [10,11], fungi, protozoa and mycobacteria [6,12]. ...
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Environmental hygiene in hospitals is a major challenge worldwide. Low-resourced hospitals in African countries continue to rely on sodium hypochlorite (NaOCl) as major disinfectant. However, NaOCl has several limitations such as the need for daily dilution, irritation, and corrosion. Hypochlorous acid (HOCl) is an innovative surface disinfectant produced by saline electrolysis with a much higher safety profile. We assessed non-inferiority of HOCl against standard NaOCl for surface disinfection in two hospitals in Abuja, Nigeria using a double-blind multi-period randomised cross-over study. Microbiological cleanliness [Aerobic Colony Counts (ACC)] was measured using dipslides. We aggregated data at the cluster-period level and fitted a linear regression. Microbiological cleanliness was high for both disinfectant (84.8% HOCl; 87.3% NaOCl). No evidence of a significant difference between the two products was found (RD = 2%, 90%CI: −5.1%–+0.4%; p-value = 0.163). We cannot rule out the possibility of HOCl being inferior by up to 5.1 percentage points and hence we did not strictly meet the non-inferiority margin we set ourselves. However, even a maximum difference of 5.1% in favour of sodium hypochlorite would not suggest there is a clinically relevant difference between the two products. We demonstrated that HOCl and NaOCl have a similar efficacy in achieving microbiological cleanliness, with HOCl acting at a lower concentration. With a better safety profile, and potential applicability across many healthcare uses, HOCl provides an attractive and potentially cost-efficient alternative to sodium hypochlorite in low resource settings.
... The change in membrane permeability allows the diffusion of oxidants to enter the cytoplasm, leading to the oxidation of proteins, which further leads to dysfunction and ultimately to the death of bacteria. The bactericidal effect, although greatly reduced, carries over to spores as well [9,10]. These findings were in line with research conducted by Kiura et al. [4] who found that electrolyzed strong acid water (ESW) created breaks and blebs in the cell membranes of Pseudomonas aeruginosa. ...
... Although anolyte is shown to be harmful to bacterial cells, it does not seem to cause any health issues or cell destruction in humans [7]. Moreover, anolyte is environmentally safe, as it eventually returns to its original saltwater state [10]. Anolyte does not affect taste, smell or the properties of organic matter. ...
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In this paper, anolyte is considered as a possible disinfectant for inhibiting the growth of bacteria in meat (beef cuts and minced pork). Meat cuts were contaminated with two concentrations of L. monocytogenes and S. Typhimurium, as these are the most common meat pathogens that are closely regulated by the EU, and treated with two different concentrations of anolyte: 20% for beef cuts and 18% for minced pork. Then, the total viable count (TVC), L. monocytogenes count and S. Typhimurium count were determined. In meat cuts and minced pork, anolyte was able to reduce TVC, S. Typhimurium and L. monocytogenes counts effectively, significantly decreasing L. monocytogenes and S. Typhimurium counts after spraying and throughout 29 days of incubation at 0–4 °C. TVC was reduced after spraying and for 10 days of incubation but later increased to be the same as before spraying with anolyte. Anolyte was effective when spraying beef cuts with a 20% solution for 60 s against pathogenic bacteria L. monocytogenes and Salmonella spp. and also when using it at a concentration of 18% from the minced meat mass. Initially, anolyte significantly decreased TVC, however during the storage period (10–29 days) TVC increased but remained significantly lower compared to control. Anolyte was effective in reducing L. monocytogenes and S. Typhimurium counts throughout the study, and after 29 days of incubation, these bacteria could not be detected in the samples treated with anolyte.
... The efficacy of electrolyzed water from super oxidation with neutral pH (SES) is the reduction of spore germination and germ tube development in fungi of postharvest importance (Gómez et al, 2017). This strong oxidation activity of EW that have already been described, where high antimicrobic effect killing bacteria, virus, fungi and parasites in a fast manner was shown, suggested that it can be utilized to disinfect surfaces and water systems (Thorn et al, 2012). In addition, there are many other "advantages" of EW over its toxic counterparts (physical, chemical and biological technology) in different areas such as agriculture, food hygiene, medical field and even in human surface disinfection" (Yan et al, 2021). ...
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The effect of electrolyzed water on phytopathogenic fungi that infect Prunus persica var. nectarine at post-harvest Efecto del agua electrolizada en fitopatógenos fungosos que afectan Prunus persica var. nectarine en postcosecha ABSTRACT Postharvest immersion of Prunus persica var. nectarine into electrolyzed water, EW (25.2 ppm of active ingredient), at different time periods of inoculation with pathogens previously isolated from rotted fruits (A, immediately before fruit immersion; B, three hours after fruit immersion and C, three hours before fruit immersion), significantly reduced fruit rotting caused by Botrytis cinerea (A: 40.2%, B: 43.1% and C: 39.1%), or by Monilinia laxa (A: 80.9%, B: 49.8% and C: 46.2%), or by Penicillium. expansum (A: 60.3%, B: 31.9% and C: 49.7%) or by Rhizopus stolonifer (A: 74.4%, B: 60.8% and C: 72.6%). Immersion of fruits into NaClO (100 ppm of active ingredient), showed significant differences with EW treatment: B. cinerea (B/NaClO: 34.5%), M. laxa (A/NaClO: 62.2%; B/NaClO: 36.2% and C/NaClO: 36.2%); P. expansum (C/NaClO: 60.9%) and R. stolonifer (A/NaClO: 81.3%; B/NaClO: 71,2% and C/NaClO: 83.9%) being in most cases, EW better than NaClO. Non inoculated fruits did not show any negative effect after treatment with EW or with NaClO. Also, IC50 values for EW and for NaClO obtained in in vitro tests for mycelia development and spore germination of the different pathogens, correlate well with the in vivo tests. All results suggest that EW can be used as an alternative method to NaClO to control postharvest fungi of Prunus persica var. nectarine fruits , considering that the exposure times and the concentration of EW may be different, depending on the pathogen to be controlled. RESUMEN Tratamientos de inmersión en postcosecha en agua eletrolizada (25,2 ppm de ingrediente activo) de frutos de Prunus persica var. nectarine, a diferentes tiempos de inoculación con patógenos aislados de frutos con pudrición (A, tratados inmediatamente antes de la inmersión del fruto; B, tres horas después de la inmersión del fruto y C, tres horas antes de la inmersión del fruto), disminuyeron significativamente la pudrición causada por Botrytis cinerea (A: 40,2%, B: 43,1% y C: 39,1%), con Monilinia laxa (A: 80,9%, B: 49,8% y C: 46,2%), con Penicillium. expansum (A: 60,3%, B: 31,9% y C: 49,7%) con Rhizopus stolonifer (A: 74,4%, B: 60,8% y C: 72,6%). Los tratamientos de inmersión de frutos en NaClO (100 ppm de ingrediente activo), mostraron diferencias significativas con los tratamientos con agua eletrolizada: B. cinerea (B/NaClO: 34,5%), M. laxa (A/NaClO: 62,2%; B/NaClO: 36,2% y C/NaClO: 36,2%); P. expansum (C/NaClO: 60,9%) y R. stolonifer (A/NaClO: 81,3%; B/NaClO: 71,2% y C/NaClO: 83,9%) siendo en la mayoría de los casos, mejor los tratamientos con agua electrolizada que con NaClO. Frutos no inoculados no mostraron un efecto negativo después del tratamiento con agua eletrolizada o con NaClO. También, los valores de IC50 con agua electrolizada o NaClO obtenidos en pruebas in vitro para el micelio y germinación de esporas de los diferentes patógenos, correlaciona bien con las pruebast in vivo. Todos los resultados sugieren que el agua electrolizada puede ser utilizada como un método alternativo al NaClO, para el control de patógenos fungosos de postcosecha en frutos de Prunus persica var. nectarine considerando que los tiempos de exposición y la concentración de agua electrolizada pueden ser diferentes, dependiendo del patógeno a controlar.
... Electrochemically activated solutions, also known as superoxidised solutions or electrolysed water, are a heterogeneous group of solutions that contain sodium hypochlorite and hypochlorous acid, among other chemical compounds, as their main active constituents Frontiers in Pharmacology | www.frontiersin.org June 2022 | Volume 13 | Article 840323 (Thorn et al., 2012;Severing et al., 2019). These solutions are available in nasal sprays such as Nasocyn (Te Arai BioFarma, Auckland, NZ). ...
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The role of bacterial biofilms in chronic and recalcitrant diseases is widely appreciated, and the treatment of biofilm infection is an increasingly important area of research. Chronic rhinosinusitis (CRS) is a complex disease associated with sinonasal dysbiosis and the presence of bacterial biofilms. While most biofilm-related diseases are associated with highly persistent but relatively less severe inflammation, the presence of biofilms in CRS is associated with greater severity of inflammation and recalcitrance despite appropriate treatment. Oral antibiotics are commonly used to treat CRS but they are often ineffective, due to poor penetration of the sinonasal mucosa and the inherently antibiotic resistant nature of bacteria in biofilms. Topical non-antibiotic antibiofilm agents may prove more effective, but few such agents are available for sinonasal application. We review compounds with antibiofilm activity that may be useful for treating biofilm-associated CRS, including halogen-based compounds, quaternary ammonium compounds and derivatives, biguanides, antimicrobial peptides, chelating agents and natural products. These include preparations that are currently available and those still in development. For each compound, antibiofilm efficacy, mechanism of action, and toxicity as it relates to sinonasal application are summarised. We highlight the antibiofilm agents that we believe hold the greatest promise for the treatment of biofilm-associated CRS in order to inform future research on the management of this difficult condition.
... Having gained wide use in the food industry, these agents are increasingly considered to be safe alternatives for advanced wound management [5]. Several studies have shown that electrolyzed acid solutions have antimicrobial activity against a wide range of Gram-positive and Gram-negative bacteria, fungi, viruses, and even microbial spores [6]. Specifically, electrolyzed acid solutions have ...
Article
Full-text available
Electrolyzed acid solutions produced by different methods have antiseptic properties due to the presence of chlorine and reactive oxygen species. Our aim was to determine whether a controlled-flow electrolyzed acid solution (CFEAS) has the ability to improve wound healing due to its antiseptic and antibiofilm properties. First, we demonstrated in vitro that Gram-negative and Gram-positive bacteria were susceptible to CFEAS, and the effect was partially sustained for 24 h, evidencing antibiofilm activity (p < 0.05, CFEAS-treated vs. controls). The partial cytotoxicity of CFEAS was mainly observed in macrophages after 6 h of treatment; meanwhile, fibroblasts resisted short-lived free radicals (p < 0.05, CFEAS treated vs. controls), perhaps through redox-regulating mechanisms. In addition, we observed that a single 24 h CFEAS treatment of subacute and chronic human wounds diminished the CFU/g of tissue by ten times (p < 0.05, before vs. after) and removed the biofilm that was adhered to the wound, as we observed via histology from transversal sections of biopsies obtained before and after CFEAS treatment. In conclusion, the electrolyzed acid solution, produced by a novel method that involves a controlled flow, preserves the antiseptic and antibiofilm properties observed in other, similar formulas, with the advantage of being safe for eukaryotic cells; meanwhile, the antibiofilm activity is sustained for 24 h, both in vitro and in vivo.
... Electrochemical disinfection has gained popularity since the 19th century due to its unique combination of electricity and chemical oxidants. 103 Several electrode materials have been employed for the application; however, comparatively high current densities and voltages are required to achieve the aimed performance. 101 Over the past years, laser-induced graphene has shown extraordinary electrical performances due to its high charge density and electron mobility, making it promising for electrochemical applications. ...
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In recent decades, there has been a growing scientific interest in various kinds of technologies using electro-activated solutions with high reactivity and representing a powerful toolkit for intensification of production processes. However, theoretical knowledge about the regularities of change in fat properties during melting in an electrolyte is rather fragmentary, scarce and often contradictory. The work is devoted to the study of the main factors influencing the change in physical and chemical properties and yield of fat in the process of melting using catholyte, to substantiate the feasibility of its use and develop an industrial line for obtaining fat. The object of studies was ostrich fat obtained by traditional method – by melting in water and by experimental technology – in catholyte as well as technological regimes of fat extraction. According to the data obtained, the fat melted at pH of catholyte 11, temperature 100 and 75 °С was characterized by low values of acid number – 0,45 mg KOH/g and 0,40 mg KOH/g, respectively. The opposite trend was observed with a successive decrease in the alkalinity of the ECA medium and an increase in the melting temperature of the fat, which led to an increase in the content of secondary oxidation products in the experimental samples. It was found that due to the high reactivity of the EСA medium, the temperature and pH of the catholyte increased, the intermolecular interaction within the fat phase decreased, which increased the mobility of lipid molecules relative to each other. The lowest values of fat viscosity (0,42 and 0,4 kPa?s) were recorded when treating fatty raw materials in catholyte with pH 10.5 and 11 and temperature 100 °С. It is shown that increasing the pH of the catholyte contributes to minimizing the values of peroxide number of ostrich fat, in contrast to the heating temperature. It is established that processing of raw materials in catholyte at 75 °C resulted in the yield of fat 88,4–90,1%, which is almost 1,4 times higher than when melted in water. In the wet method of mellowing in water, denaturation of protein structures and a higher degree of fat extraction can be achieved at a mellowing temperature above 75 °C, in contrast to the proposed method of processing raw materials.
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Abstract: In this review electrolytic hypochlorous acid generators were investigated and their advantages and disadvantages were identified. Hypochlorous acid is a highly efficient solution for sanitizing and one hundred percent safe for human use but like all disinfection solutions, it has some disadvantages, such as low shelf life in some cases, can damage skin in high chlorine concentrations and it can cause corrosion in metals, etc. In general, bacteria, pathogens and viruses surrounded us. The hypochlorous acid could be used as disinfection solution for confronting this danger. Producing hypochlorous acid is commercial issue and companies do not allow to other people for having access to their mechanism that used for producing hypochlorous acid. So, for this case of study, emails were sent to approximately 110 companies that supply hypochlorous acid generators or producers of hypochlorous acid in the world. Only a few of them responded, about 2 companies cooperated and filled the tables that I prepared and about 3 people sent me some papers. This final report has been written according to these responded and 270 papers that I read. The result is a classification of four models of devices that produce hypochlorous acid through electrolysis from the past to the present and evaluation of the advantages and disadvantages of these four main models. Also, some criteria have been written for the feed quality of these cells, quality criteria of and the maintenance of these cell parts because these devices have ideal operating conditions and these conditions should be considered to produce better hypochlorous acid with longer shelf life. In the following, an economic review has been written on these electrolytic cells for producing hypochlorous acid. For this case of study, the technical and economic information of the available devices has been collected. Also, to better communicate with companies that active in production of hypochlorous acid, their page addresses and contact emails have been written in appendices chapter. Based on technical and economic information, results have been obtained regarding the prices and efficiency of these hypochlorous acid generators. Also, in this work, the main problems of these devices were investigated and some recommendations have been written in the recommendation chapter to improve these problems. These recommendations are related to best device that could produce hypochlorous acid, corrosion on anode, fouling formation on the cathode, low shelf life of the hypochlorous acid, modeling the space between electrodes by simulation software and control system, etc. Also, some recommendations have been written about replacing power supply of the electrolytic cells devices by using renewable energy devices. Key Word: HOCl, Hypochlorous acid, Process for Producing HOCl, Hypochlorous Acid Generators, Electrolysis Systems, Electrolytic Cells.
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We investigated the minimum bactericidal concentrations of aqua oxidation water and three disinfectants used as controls to 8 methicillin-resistant staphylococci and 4 standard strains of Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Candida albicans. Undiluted aqua oxidation water was effective against all strains tested, although it allowed growth of S. aureus and C. albicans at 4-fold dilution, and S. aureus at 2-fold dilution. The three disinfectants used as controls were effective against almost all strains tested. These results suggest that the bactericidal activity of undiluted aqua oxidation water is equal to or greater than that of the three disinfectants used as controls.
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Acute and prolonged oral toxicity tests were made of superoxidized water on Crj:CD (SD) rats; the animals were 5 weeks old at the beginning of each experiment. In the acute study, superoxidized water was administered orally by gavage to 5 male and 5 female rats at 50 ml/kg (the highest practical dose). Thereafter the rats were observed for 14 days. No deaths occurred. There were no abnormalities in the general conditions or body weight, or on necropsy. Thus, the LD50 value of the test water was more than 50 ml/kg for both sexes. In the prolonged study male and female rats (10/sex) were allowed free access to the superoxidized water via water bottles for 28 days. Control rats were given the tap water (chlorinated, the Hita City supply) in the same way. The mean consumption of the water were 109.0 g/kg/day in males and 117.8 g/kg/day in females. The test water caused no deaths and no treatment-related changes in the general conditions, body weight on food consumption. The treated animals of both sexes showed a decrease in water consumption during the dosing period and a decrease in urine volume in urinalysis at the end of the dosing period. In the urinalysis, the treated group showed increases in some parameters per unit volume but no change in terms of the total amount of urine excreted during a given period. In blood chemistry, hematology and histopathology treatment-related changes included increased GPT in both sexes, prolonged activated partial thromboplastin time and increased triglyceride in males and decreased total cholesterol in females, and hypersecretion of the jejunum or duodenum in some males. All these changes were slight, however. In conclusion, oral administration of superoxidized water affects the function of the liver in both sexes and the small intestine in males, but these effects are not serious.