Inhibition of biofilms by glucose oxidase, lactoperoxidase and guaiacol: the active antibacterial component in an enzyme alginogel

Microbial Biofilm Inhibition Using Magnetic Cross-Linked Polyphenol Oxidase Aggregates

Microbial biofilm accumulation poses a serious threat to the environment, presents significant challenges to different industries, and exhibits a large impact on public health. Since there has not been a conclusive answer found despite various efforts, the potential green and economical methods are being focused on, particularly the innovative approaches that employ biochemical agents. In the present study, we propose a bio-nanotechnological method using magnetic cross-linked polyphenol oxidase aggregates (PPO m-CLEA) for inhibition of microbial biofilm including multidrug resistant bacteria. Free PPO solution showed only 55-60% biofilm inhibition, whereas m-CLEA showed 70-75% inhibition, as confirmed through microscopic techniques. The carbohydrate and protein contents in biofilm extracellular polymeric substances (EPSs) were reduced significantly. The m-CLEA demonstrated reusability up to 5 cycles with consistent efficiency in biofilm inhibition. Computational work was also done where molecular docking of PPO with microbial proteins associated with biofilm formation was conducted, resulting in favorable binding scores and inter-residual interactions. Overall, both in vitro and in silico results suggest that PPO interferes with microbial cell attachment and EPS formation, thereby preventing biofilm colonization.

Antibacterial mechanism of linalool emulsion against Pseudomonas aeruginosa and its application to cold fresh beef

Pseudomonas aeruginosa (P. aeruginosa) is the dominant spoilage bacterium in cold fresh beef. The current strategy is undertaken to overcome the low water solubility of linalool by encapsulating linalool into emulsions. The results of field emission scanning electron microscopy and particle size distribution revealed that the appearance of the bacterial cells was severely disrupted after exposure to linalool emulsion (LE) with an minimum inhibitory concentration (MIC) of 1.5 mL/L. Probes combined with fluorescence spectroscopy were performed to detect cell membrane permeability, while intracellular components (protein and ion leakage) and crystal violet staining were further measured to characterize cell membrane integrity and biofilm formation ability. The results confirmed that LE could destroy the structure of the cell membrane, thereby leading to the leakage of intracellular material and effective removal of biofilms. Molecular docking confirmed that LE can interact with the flagellar cap protein (FliD) and DNA of P. aeruginosa, inhibiting biofilm formation and causing genetic damage. Furthermore, the results of respiratory metabolism and reactive oxygen species (ROS) accumulation revealed that LE could significantly inhibit the metabolic activity of P. aeruginosa and induce oxidative stress. In particular, the inhibition rate of LE on P. aeruginosa was 23.03% and inhibited mainly the tricarboxylic acid cycle (TCA). Finally, LE was applied to preserve cold fresh beef, and the results showed that LE could effectively inhibit the activity of P. aeruginosa and delay the quality change of cold fresh beef during the storage period. These results are of great significance to developing natural preservatives and extending the shelf life of cold fresh beef.

Methyltransferase as Antibiotics Against Foodborne Pathogens: An In Silico Approach for Exploring Enzyme as Enzymobiotics

The development of resistance in microbes against antibiotics and limited choice for the use of chemical preservatives in food lead the urgent need to search for an alternative to antibiotics. The enzymes are catalytic proteins that catalyze digestion of bacterial cell walls and protein requirements for the survival of the cell. To study methyltransferase as antibiotics against foodborne pathogen, the methyltransferase enzyme sequence was modeled and its interactions were analyzed against a membrane protein of the gram-positive and gram-negative bacteria through in silico protein-protein interactions. The methyltransferase interaction with cellular protein was found to be maximum, due to the maximum PatchDock Score (15808), which was followed by colicin (12864) and amoxicillin (4122). The modeled protein has found to be interact more significantly to inhibit the indicator bacteria than the tested antibiotics and antimicrobial colicin protein. Thus, model enzyme methyltransferase could be used as enzymobiotics. Moreover, peptide sequences similar to this enzyme sequence need to be designed and evaluated against the microbial pathogen.

Therapy of infected wounds: overcoming clinical challenges by advanced drug delivery systems

In recent years, the incidence of infected wounds is steadily increasing, and so is the clinical as well as economic interest in effective therapies. These combine reduction of pathogen load in the wound with general wound management to facilitate the healing process. The success of current therapies is challenged by harsh conditions in the wound microenvironment, chronicity, and biofilm formation, thus impeding adequate concentrations of active antimicrobials at the site of infection. Inadequate dosing accuracy of systemically and topically applied antibiotics is prone to promote development of antibiotic resistance, while in the case of antiseptics, cytotoxicity is a major problem. Advanced drug delivery systems have the potential to enable the tailor-made application of antimicrobials to the side of action, resulting in an effective treatment with negligible side effects. This review provides a comprehensive overview of the current state of treatment options for the therapy of infected wounds. In this context, a special focus is set on delivery systems for antimicrobials ranging from semi-solid and liquid formulations over wound dressings to more advanced carriers such as nano-sized particulate systems, vesicular systems, electrospun fibers, and microneedles, which are discussed regarding their potential for effective therapy of wound infections. Further, established and novel models and analytical techniques for preclinical testing are introduced and a future perspective is provided.

The use of hydrogen peroxide in the treatment of burn wound infection: a systematic review, and survey of current clinical practice in the United Kingdom

BACKGROUND

Current treatment of burn wound infection (BWI) is with antibiotics and/or wound cleaning/superficial debridement. The overuse of antibiotics has contributed to antibiotic resistance. One possible solution is the use of hydrogen peroxide (H₂O₂). The aim of this study is to investigate the current use of H₂O₂ in the treatment of BWI through a comprehensive review of published evidence and a survey of current clinical practice.

METHODS

A systematic review was performed on the clinical use of H₂O₂ in the treatment of BWI using four major search engines from inception to 1^st July 2018. English-written full-text publications of any study design were included and data extraction was conducted in duplicate. An 11-question survey on the use of H₂O₂ in the treatment of BWI was sent to all burn services in the United Kingdom (UK).

RESULTS

The systematic review generated 1,168 papers, with only one fulfilling inclusion criteria. This was a randomised control trial (RCT) which demonstrated that soaking grafts with 2% H₂O₂ prior to grafting improved graft take rate in infected burn wounds compared with grafts treated with saline prior to grafting, concluding that H₂O₂ can be recommended in the treatment of BWI intraoperatively. A 72.7% (16 burns services) response rate was achieved to the survey. Of these, 75% of burn services (n = 12) do not currently use H₂O₂ in clinical practice. Of the 25% (n = 4) which do use H₂O₂, no service had a protocol for its use. The most common reasons for not using H₂O₂ were a lack of published evidence and fear of side-effects.

CONCLUSION

Only 1 paper suggests H₂O₂ to be effective in BWI treatment and there is no national consistency or protocol for the use of H₂O₂ in the treatment of BWI in the UK. More large-scale research is required to determine whether H₂O₂ may offer a solution to the need to use antibiotics to treat BWI.

Antimicrobial Activity of Naturally Occurring Phenols and Derivatives Against Biofilm and Planktonic Bacteria

Biofilm-forming bacteria present formidable challenges across diverse settings, and there is a need for new antimicrobial agents that are both environmentally acceptable and relatively potent against microorganisms in the biofilm state. The antimicrobial activity of three naturally occurring, low molecular weight, phenols, and their derivatives were evaluated against planktonic and biofilm Staphylococcus epidermidis and Pseudomonas aeruginosa. The structure activity relationships of eugenol, thymol, carvacrol, and their corresponding 2- and 4-allyl, 2-methallyl, and 2- and 4-n-propyl derivatives were evaluated. Allyl derivatives showed a consistent increased potency with both killing and inhibiting planktonic cells but they exhibited a decrease in potency against biofilms. This result underscores the importance of using biofilm assays to develop structure-activity relationships when the end target is biofilm.

Antimicrobial Activity and Proposed Action Mechanism of 3-Carene against Brochothrix thermosphacta and Pseudomonas fluorescens

3-Carene is an antimicrobial monoterpene that occurs naturally in a variety of plants and has an ambiguous antibacterial mechanism against food-borne germs. The antibacterial effects and action mechanism of 3-carene against Gram-positive Brochothrix thermosphacta ACCC 03870 and Gram-negative Pseudomonas fluorescens ATCC 13525 were studied. Scanning electron microscopy (SEM) examination and leakage of alkaline phosphatase (AKP) verified that 3-carene caused more obvious damage to the morphology and wall structure of B. thermosphacta than P. fluorescens. The release of potassium ions and proteins, the reduction in membrane potential (MP), and fluorescein diacetate (FDA) staining further confirmed that the loss of the barrier function of the cell membrane and the leakage of cytoplasmic contents were due to the 3-carene treatment. Furthermore, the disorder of succinate dehydrogenase (SDH), malate dehydrogenase (MDH), pyruvate kinase (PK), and ATP content indicated that 3-carene could lead to metabolic dysfunction and inhibit energy synthesis. In addition, the results from the fluorescence analysis revealed that 3-carene could probably bind to bacterial DNA and affect the conformation and structure of genomic DNA. These results revealed that 3-carene had strong antibacterial activity against B. thermosphacta and P. fluorescens via membrane damage, bacterial metabolic perturbations, and genomic DNA structure disruption, interfering in cellular functions and even causing cell death.

Innovative drugs, chemicals, and enzymes within the animal production chain

The alarming number of recently reported human illnesses with bacterial infections resistant to multiple antibacterial agents has become a serious concern in recent years. This phenomenon is a core challenge for both the medical and animal health communities, since the use of antibiotics has formed the cornerstone of modern medicine for treating bacterial infections. The empirical benefits of using antibiotics to address animal health issues in animal agriculture (using therapeutic doses) and increasing the overall productivity of animals (using sub-therapeutic doses) are well established. The use of antibiotics to enhance profitability margins in the animal production industry is still practiced worldwide. Although many technical and economic reasons gave rise to these practices, the continued emergence of antimicrobial resistant bacteria is furthering the need to reduce the use of medically important antibiotics. This will require improving on-farm management and biosecurity practices, and the development of effective antibiotic alternatives that will reduce the dependence on antibiotics within the animal industry in the foreseeable future. A number of approaches are being closely scrutinized and optimized to achieve this goal, including the development of promising antibiotic alternatives to control bacterial virulence through quorum-sensing disruption, the use of synthetic polymers and nanoparticles, the exploitation of recombinant enzymes/proteins (such as glucose oxidases, alkaline phosphatases and proteases), and the use of phytochemicals. This review explores the most recent approaches within this context and provides a summary of practical mitigation strategies for the extensive use of antibiotics within the animal production chain in addition to several future challenges that need to be addressed.

[Wound management with enzyme alginogels : Expert consensus]

BACKGROUND

The challenges of modern wound management, such as the treatment of chronic wounds and their phase-specific handling, are demanding and require optimally adapted therapeutic measures. The principles of moist wound care as well as an adequate debridement have priority here. To support these necessary measures, different options are available, e.g., a new product group operating across several wound phases.

OBJECTIVE

A new treatment principle in modern wound management based on an expert consensus is presented.

METHODS

On the basis of clinical experience reports and published evidence, the current and new principles of wound treatment were discussed in a panel of experts and formulated as a consensus statement.

RESULTS

Enzyme alginogels represent a combination of agents that allow phase-specific wound care. They exhibit autolytic, absorbent, and antimicrobial properties and simultaneously cover three components of wound management based on the TIME framework. Thus, according to the experts, they differ from other wound healing products and can be classified in a distinct product group. Clinical studies, as well as clinical experiences, provide evidence for the efficacy of enzyme alginogels.

DISCUSSION

According to the experts, the potential of enzyme alginogels used considering the principles of moist wound care, comprises the three-fold effect (continuous and significantly simplified debridement, maintaining a moist wound environment and antimicrobial effect without cytotoxicity), the ease of use, and the flexible application. In addition, the flexibility of the product class regarding frequency of application, duration of treatment and combinability with secondary dressings, are of economic benefit in the health care sector.

Candida species biofilm and Candida albicans ALS3 polymorphisms in clinical isolates

Over the last decades, there have been important changes in the epidemiology of Candida infections. In recent years, Candida species have emerged as important causes of invasive infections mainly among immunocompromised patients. This study analyzed Candida spp. isolates and compared the frequency and biofilm production of different species among the different sources of isolation: blood, urine, vulvovaginal secretions and peritoneal dialysis fluid. Biofilm production was quantified in 327 Candida isolates obtained from patients attended at a Brazilian tertiary public hospital (Botucatu, Sao Paulo). C. albicans ALS3 gene polymorphism was also evaluated by determining the number of repeated motifs in the central domain. Of the 198 total biofilm-positive isolates, 72 and 126 were considered as low and high biofilm producers, respectively. Biofilm production by C. albicans was significantly lower than that by non-albicans isolates and was most frequently observed in C. tropicalis. Biofilm production was more frequent among bloodstream isolates than other clinical sources, in urine, the isolates displayed a peculiar distribution by presenting two distinct peaks, one containing biofilm-negative isolates and the other containing isolates with intense biofilm production. The numbers of tandem-repeat copies per allele were not associated with biofilm production, suggesting the evolvement of other genetic determinants.

Biofilms in wounds: a review of present knowledge

Following confirmation of the presence of biofilms in chronic wounds, the term biofilm became a buzzword within the wound healing community. For more than a century pathogens have been successfully isolated and identified from wound specimens using techniques that were devised in the nineteenth century by Louis Pasteur and Robert Koch. Although this approach still provides valuable information with which to help diagnose acute infections and to select appropriate antibiotic therapies, it is evident that those organisms isolated from clinical specimens with the conditions normally used in diagnostic laboratories are mainly in a planktonic form that is unrepresentative of the way in which most microbial species exist naturally. Usually microbial species adhere to each other, as well as to living and non-living surfaces, where they form complex communities surrounded by collectively secreted extracellular polymeric substances (EPS). Cells within such aggregations (or biofilms) display varying physiological and metabolic properties that are distinct from those of planktonic cells, and which contribute to their persistence. There are many factors that influence healing in wounds and the discovery of biofilms in chronic wounds has provided new insight into the reasons why. Increased tolerance of biofilms to antimicrobial agents explains the limited efficacy of antimicrobial agents in chronic wounds and illustrates the need to develop new management strategies. This review aims to explain the nature of biofilms, with a view to explaining their impact on wounds.

Lactoferrin, myeloperoxidase, and ceruloplasmin: complementary gearwheels cranking physiological and pathological processes

Copper-containing plasma protein ceruloplasmin (Cp) forms a complex with lactoferrin (Lf), an iron-binding protein, and with the heme-containing myeloperoxidase (Mpo). In case of inflammation, Lf and Mpo are secreted from neutrophil granules. Among the plasma proteins, Cp seems to be the preferential partner of Lf and Mpo. After an intraperitoneal injection of Lf to rodents, the "Cp-Lf" complex has been shown to appear in their bloodstream. Cp prevents the interaction of Lf with protoplasts of Micrococcus luteus. Upon immunoprecipitation of Cp, the blood plasma becomes depleted of Lf and in a dose-dependent manner loses the capacity to inhibit the peroxidase activity of Mpo, but not the Mpo-catalyzed oxidation of thiocyanate in the (pseudo)halogenating cycle. Antimicrobial effect against E. coli displayed by a synergistic system that includes Lf and Mpo-H2O2-chloride, but not thiocyanate, as the substrate for Mpo is abrogated when Cp is added. Hence, Cp can be regarded as an anti-inflammatory factor that restrains the halogenating cycle and redirects the synergistic system Mpo-H2O2-chloride/thiocyanate to production of hypothiocyanate, which is relatively harmless for the human organism. Structure and functions of the "2Cp-2Lf-Mpo" complex and binary complexes Cp-Lf and 2Cp-Mpo in inflammation are discussed.

Inhibition of biofilms of Pseudomonas aeruginosa by Medihoney in vitro

OBJECTIVE

Pseudomonas aeruginosa has been linked to chronic wound infections, where its ability to form biofilms and to tolerate antimicrobial agents helps to facilitate its persistence. This study aimed to investigate the susceptibility of biofilms of Pseudomonas aeruginosa to Medihoney in vitro.

METHOD

Biofilms were cultivated in microtitre plates with and without a range of concentrations of Medihoney, and effects on biofilm were monitored by optical density (at 650nm), biomass (by staining with crystal violet), metabolic activity (using an esterase assay) and viability (by determining total cell counts). Structural effects on established biofilms were examined by scanning electron microscopy and epifluorescence following staining by LIVE/DEAD® BacLight, which also showed effects on vitality.

RESULTS

The lowest concentration of Medihoney found to prevent biofilm formation was 17%(w/v), whereas on average 35.5%(w/v) of Medihoney was required to inhibit established biofilms. Susceptibility did not vary with length of biofilm establishment between 24 and 72 hours. Extensive structural changes in established biofilms were seen in the sample with less than or equal to 30%(w/v) Medihoney using scanning electron microscopy and loss of viability was found in test samples with less than or equal to 20%(w/v) Medihoney concentration using fluorescent staining, together with loss of biofilm structure.

CONCLUSION

Using a range of methods to evaluate biofilm integrity, this study demonstrates that Medihoney inhibits Pseudomonas aeruginosa biofilms in vitro at concentrations that are attainable in clinical use. Whether Medihoney has the potential to disrupt Pseudomonas aeruginosa biofilms in cutaneous wounds must now be tested in patients.

DECLARATION OF INTEREST

This study was sponsored by Derma Sciences Inc, NJ. An unrestricted grant was provided and the sponsors were not involved in the design of the experiments or the preparation of this manuscript.

Antibiotic alternatives: the substitution of antibiotics in animal husbandry?

It is a common practice for decades to use of sub-therapeutic dose of antibiotics in food-animal feeds to prevent animals from diseases and to improve production performance in modern animal husbandry. In the meantime, concerns over the increasing emergence of antibiotic-resistant bacteria due to the unreasonable use of antibiotics and an appearance of less novelty antibiotics have prompted efforts to develop so-called alternatives to antibiotics. Whether or not the alternatives could really replace antibiotics remains a controversial issue. This review summarizes recent development and perspectives of alternatives to antibiotics. The mechanism of actions, applications, and prospectives of the alternatives such as immunity modulating agents, bacteriophages and their lysins, antimicrobial peptides, pro-, pre-, and synbiotics, plant extracts, inhibitors targeting pathogenicity (bacterial quorum sensing, biofilm, and virulence), and feeding enzymes are thoroughly discussed. Lastly, the feasibility of alternatives to antibiotics is deeply analyzed. It is hard to conclude that the alternatives might substitute antibiotics in veterinary medicine in the foreseeable future. At the present time, prudent use of antibiotics and the establishment of scientific monitoring systems are the best and fastest way to limit the adverse effects of the abuse of antibiotics and to ensure the safety of animal-derived food and environment.

Biofilm-degrading enzymes from Lysobacter gummosus

Biofilm-degrading enzymes could be used for the gentle cleaning of industrial and medical devices and the manufacture of biofilm-resistant materials. We therefore investigated 20 species and strains of the bacterial genus Lysobacter for their ability to degrade experimental biofilms formed by Staphylococcus epidermidis, a common nosocomial pathogen typically associated with device-related infections. The highest biofilm-degradation activity was achieved by L. gummosus. The corresponding enzymes were identified by sequencing the L. gummosus genome. Partial purification of the biofilm-degrading activity from an extract of extracellular material followed by peptide mass fingerprinting resulted in the identification of two peptidases (α-lytic protease and β-lytic metalloendopeptidase) that were predicted to degrade bacterial cell walls. In addition, we identified two isoforms of a lysyl endopeptidase and an enzyme similar to metalloproteases from Vibrio spp. Potential peptidoglycan-binding C-terminal fragments of two OmpA-like proteins also co-purified with the biofilm-degrading activity. The L. gummosus genome was found to encode five isoenzymes of α-lytic protease and three isoenzymes of lysyl endopeptidase. These results indicated that the extracellular digestion of biofilms by L. gummosus depends on multiple bacteriolytic and proteolytic enzymes, which could now be exploited for biofilm control.

Inhibition of biofilms by glucose oxidase, lactoperoxidase and guaiacol: the active antibacterial component in an enzyme alginogel

The association of biofilms with wound chronicity has prompted a search for antimicrobial interventions that are effective against biofilms. A patented preparation of glucose oxidase, lactoperoxidase and guaiacol (GLG), which is the antibacterial component of Flaminal, has been shown to inhibit a wide range of bacteria, but it has not yet been tested on biofilms. This study aims to determine the effect of GLG on biofilms of Staphylococcus aureus, methicillin-resistant S. aureus and Pseudomonas aeruginosa. Static biofilms were grown in microtitre plates and on coverslips and treated with a range of concentrations of GLG. Effects were monitored by estimating biofilm biomass by staining with crystal violet, biofilm activity by staining with either resazurin or fluorescein diacetate and biofilm viability by staining with LIVE/DEAD BacLight Bacterial Viability Kit. GLG was able to prevent the formation of biofilms at concentration ≤0.5% (w/v) and higher concentrations were required to inhibit established biofilms. GLG did not disrupt biofilm biomass. Staphylococci were more susceptible to GLG than P. aeruginosa. These in vitro findings must be verified by in vivo studies.