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.

Traditional microbiological techniques are used to provide reliable data on the rate and extent of kill for a range of biocides. However, such techniques provide very limited data regarding the initial rate of kill of fast-acting biocides over very short time domains. This study describes the application of a recombinant strain of Escherichia coli expressing the Photorhabdus luminescens lux operon as a whole-cell biosensor. Light emission is linked directly to bacterial metabolism; therefore, by monitoring light output, the impact of fast-acting biocides can be assessed. Electrochemically activated solutions (ECASs), bleach, Virkon, and ethanol were assessed at three concentrations (1%, 10%, 80%) in the presence of organic soiling. Over a 2-s time course, 80% ECAS produced the greatest reduction in light output in the absence of organic load but was strongly inhibited by its presence. Eighty percent ethanol outperformed all tested biocides in the presence of organic soil. Bleach and Virkon produced similar reductions in bioluminescence at matched concentrations within the time course of the assay. It was also demonstrated that the assay can be used to rapidly assess the impact of organic soiling. The use of bioluminescent bacteria as whole-cell bioreporters allows assessment of the relative efficacies of fast-acting biocides within milliseconds of application. The assay can be used to investigate activity over short or extended time domains to confirm complete metabolic inhibition of the bioreporter. Moreover, the assay may enable further elucidation of their mechanism of action by allowing the investigation of activity over time domains precluded by traditional microbiology.The efficacy of electrochemically activated solutions (ECASs) as fast-acting bactericidal and sporicidal biocides active against a range of organisms has been previously reported (26). It was noted that traditional microbiological methods were limiting in terms of elucidating the efficacy of biocides with a rapid mode of action, particularly during the early stages of kill. Loshon et al. (18) had similar difficulties when assessing the kill rate of a related biocide against spores of Bacillus subtilis. Traditional recovery count methods are limited by the frequency of the sampling time and the duration required to transfer the sample to a neutralizing diluent. This limitation is exacerbated when examining fast-acting biocides, where the time required for removal of a sample and adequate mixing with a neutralizer may be significant in terms of the kill kinetics. Few studies directly compare biocides using suitable methods, and the availability of simple, nonspecific tests is of benefit to users in selecting a biocide appropriate to their needs (31). This study describes a real-time technique, utilizing bioluminescent bacteria as whole-cell bioreporters of the very early stage of kill, for a range of fast-acting biocides under clean and dirty conditions.Bioluminescence occurs throughout nature in many species, the most abundant of which are ...

Aims:  Electrochemically activated solutions (ECAS) are generated from halide salt solutions via specially designed electrolytic cells. The active solutions are known to possess high biocidal activity against a wide range of target microbial species, however, literature revealing the kill‐kinetics of these solutions is limited. The aim of the study was to identify the kill‐rate and extent of population kill for a range of target species (including endospores) using ECAS generated at the anode (anolyte). Methods and Results:  Standard suspensions of methicillin‐resistant Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus atrophaeus spores and Clostridium difficile spores were treated with anolyte in a quantitative suspension assay. For vegetative cells, all concentrations of anolyte tested reduced the viable population to below the detection limit within 10 s. At a concentration of 99%, anolyte produced a log10 reduction factor of greater than five in viable B. atrophaeus endospores within 90 s and reduced numbers of C. difficile endospores to below the experimental detection limit within 20 s at concentrations of 5% or greater. Conclusions:  Anolyte was highly effective in killing test‐bacteria and spores. The bactericidal efficacy was retained against vegetative cells at dilutions as low as 1% and against C. difficile spores as low as 5%. Significance and Impact of Study:  The results of this study demonstrate that ECAS are effective at lower concentrations and act more rapidly than previously reported. Potent bactericidal and sporicidal activity coupled with point‐of‐use generation, low production‐costs and environmental compatibility suggest that acidic ECAS has the potential to be a useful addition to the current armoury of disinfectants.

Staphylococcus aureus is a Gram-positive pathogen responsible for a variety of infections, and some strains are resistant to virtually all classes of antibiotics. Cell shaving proteomics using a novel probability scoring algorithm to compare the surfaceomes of the methicillin-resistant, laboratory-adapted S. aureus COL strain with a COL strain in vitro adapted to high levels of oxacillin (APT). APT displayed altered cell morphology compared with COL and increased aggregation in biofilm assays. Increased resistance to β-lactam antibiotics was observed, but adaptation to oxacillin did not confer multidrug resistance. Analysis of the S. aureus COL and APT surfaceomes identified 150 proteins at a threshold determined by the scoring algorithm. Proteins unique to APT included the LytR-CpsA-Psr (LCP) domain-containing MsrR and SACOL2302. Quantitative RT-PCR showed increased expression of sacol2302 in APT grown with oxacillin (>6-fold compared with COL). Overexpression of sacol2302 in COL to levels consistent with APT (+ oxacillin) did not influence biofilm formation or β-lactam resistance. Proteomics using iTRAQ and LC-MS/MS identified 1323 proteins (∼50% of the theoretical S. aureus proteome), and cluster analysis demonstrated elevated APT abundances of LCP proteins, capsule and peptidoglycan biosynthesis proteins, and proteins involved in wall remodelling. Adaptation to oxacillin also induced urease proteins, which maintained culture pH compared to COL. These results show that S. aureus modifies surface architecture in response to antibiotic adaptation.

The main aim of this study was to develop a standardized experimental assay to enable differential antimicrobial comparisons of test biocidal aerosols. This study represents the first chlorine-matched comparative assessment of the antimicrobial activities of aerosolized sodium hypochlorite, chlorine dioxide, and electrochemically activated solution (ECAS) to determine their relative abilities to decontaminate various surface-associated health care-relevant microbial challenges. Standard microbiological challenges were developed by surface-associating typed Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis spores, or a clinical methicillin-resistant S. aureus (MRSA) strain on stainless steel, polypropylene, or fabric. All test coupons were subjected to 20-min biocidal aerosols of chlorine-matched (100 ppm) sodium hypochlorite, chlorine dioxide, or ECAS within a standard aerosolization chamber using a commercial humidifier under defined conditions. Biocidal treatment type and material surface had a significant effect on the number of microorganisms recovered from various material surfaces following treatment exposure. Under the conditions of the assay, the order of antimicrobial efficacy of biocidal aerosol treatment was as follows: ECAS > chlorine dioxide > sodium hypochlorite. For all biocides, greater antimicrobial reductions were seen when treating stainless steel and fabric than when treating plastic-associated microorganisms. The experimental fogging system and assay protocol designed within this study were shown capable of differentiating the comparative efficacies of multiple chlorine-matched biocidal aerosols against a spectrum of target organisms on a range of test surface materials and would be appropriate for testing other biocidal aerosol treatments or material surfaces.

Electrochemically activated solutions (ECAS) are generated by electrolysis of NaCl solutions, and demonstrate broad spectrum antimicrobial activity and high environmental compatibility. The biocidal efficacy of ECAS at the point of production is widely reported in the literature, as are its credentials as a “green biocide.” Acidic ECAS are considered most effective as biocides at the point of production and ill suited for extended storage. Acidic ECAS samples were stored at 4 °C and 20 °C in glass and polystyrene containers for 398 days, and tested for free chlorine, pH, ORP and bactericidal activity throughout. ORP and free chlorine (mg/L) in stored ECAS declined over time, declining at the fastest rate when stored at 20 °C in polystyrene and at the slowest rate when stored at 4 °C in glass. Bactericidal efficacy was also affected by storage and ECAS failed to produce a 5 log10 reduction on five occasions when stored at 20 °C. pH remained stable throughout the storage period. This study represents the longest storage evaluation of the physiochemical parameters and bactericidal efficacy of acidic ECAS within the published literature and reveals that acidic ECAS retain useful bactericidal activity for in excess of 12 months, widening potential applications.

Background Enteric infections caused by Salmonella spp. remain a major public health burden worldwide. Chickens are known to be a major reservoir for this zoonotic pathogen. The presence of Salmonella in poultry farms and abattoirs is associated with financial costs of treatment and a serious risk to human health. The use of bacteriophages as a biocontrol is one possible intervention by which Salmonella colonization of chickens could be reduced. In a prior study, phages Eϕ151 and Tϕ7 significantly reduced broiler chicken caecal colonization by S. Enteritidis and S. Typhimurium respectively. Methods Salmonella -free Ross broiler chickens were orally infected with S. Enteritidis P125109 or S. Typhimurium 4/74. After 7 days of infection, the animals were euthanased, and 25cm 2 sections of skin were collected. The skin samples were sprayed with a phage suspension of either Eϕ151 ( S. Enteritidis), Tϕ7 phage suspension ( S. Typhimurium) or SM buffer (Control). After incubation, the number of surviving Salmonella s was determined by direct plating and Most Probable Number (MPN). To determine the rate of reduction of Salmonella numbers on the skin surface, a bioluminescent S . Typhimurium DT104 strain was cultured, spread on sections of chicken breast skin, and after spraying with a Tϕ11 phage suspension, skin samples were monitored using photon counting for up to 24 h. Results The median levels of Salmonella reduction following phage treatment were 1.38 log 10 MPN (Enteritidis) and 1.83 log 10 MPN (Typhimurium) per skin section. Treatment reductions were significant when compared with Salmonella recovery from control skin sections treated with buffer ( p < 0.0001). Additionally, significant reduction in light intensity was observed within 1 min of phage Tϕ11 spraying onto the skin contaminated with a bioluminescent Salmonella recombinant strain, compared with buffer-treated controls ( p < 0.01), implying that some lysis of Salmonella was occurring on the skin surface. Conclusions The results of this study suggest that phages may be used on the surface of chicken skin as biocontrol agents against Salmonella infected broiler chicken carcasses. The rate of bioluminescence reduction shown by the recombinant Salmonella strain used supported the hypothesis that at least some of the reduction observ...

Tumour microenvironments are hallmarked in many cancer types. In haematological malignancies, bone marrow (BM) mesenchymal stromal cells (MSC) protect malignant cells from drug-induced cytotoxicity. However, less is known about malignant impact on supportive stroma. Notably, it is unknown whether these interactions alter long-term genotoxic damage in either direction. The nucleoside analogue cytarabine (ara-C), common in haematological therapies, remains the most effective agent for acute myeloid leukaemia, yet one third of patients develop resistance. This study aimed to evaluate the bidirectional effect of MSC and malignant cell co-culture on ara-C genotoxicity modulation. Primary MSC, isolated from patient BM aspirates for haematological investigations, and malignant haematopoietic cells (leukaemic HL-60) were co-cultured using trans-well inserts, prior to treatment with physiological dose ara-C. Co-culture genotoxic effects were assessed by micronucleus and alkaline comet assays. Patient BM cells from chemotherapy-treated patients had reduced ex vivo survival (P = 0.0049) and increased genotoxicity (P = 0.3172) than untreated patients. It was shown for the first time that HL-60 were protected by MSC from ara-C-induced genotoxicity, with reduced MN incidence in co-culture as compared to mono-culture (P = 0.0068). Comet tail intensity also significantly increased in ara-C-treated MSC with HL-60 influence (P = 0.0308). MSC sensitisation to ara-C genotoxicity was also demonstrated following co-culture with HL60 (P = 0.0116), which showed significantly greater sensitisation when MSC-HL-60 co-cultures were exposed to ara-C (P = 0.0409). This study shows for the first time that malignant HSC and MSC bidirectionally modulate genotoxicity, providing grounding for future research identifying mechanisms of altered genotoxicity in leukaemic microenvironments. MSC retain long-term genotoxic and functional damage following chemotherapy exposure. Understanding the interactions perpetuating such damage may inform modifications to reduce therapy-related complications, such as secondary malignancies and BM failure.