The antibacterial activity of honey derived from Australian flora

The Therapeutic Mechanisms of Honey in Mitigating Toxicity from Anticancer Chemotherapy Toxicity: A Review

Within the domain of conventional oncochemotherapeutics, anticancer chemotherapy (AC) has emerged as a potent strategy for the treatment of cancers. AC is the mainstay strategy for solid and non-solid cancer treatment. Its mechanistic action targets the blockage of DNA transcription and the dysregulation of cell cycle machinery in cancer cells, leading to the activation of death pathways. However, the attendant side effect of toxicity inflicted by AC on healthy tissues presents a formidable challenge. The crucial culprit in the AC side effect of toxicity is unknown, although oxidative stress, mitochondrial impairment, inflammatory cascades, autophagy dysregulation, apoptosis, and certain aberrant signaling have been implicated. Honey is a natural bee product with significant health benefits and pharmacological properties. Interestingly, the literature reports that honey may proffer a protection mechanism for delicate tissue/organs against the side effect of toxicity from AC. Thus, this review delves into the prospective role of honey as an alleviator of the AC side effect of toxicity; it provides an elucidation of the mechanisms of AC toxicity and honey's molecular mechanisms of mitigation. The review endeavors to unravel the specific molecular cascades by which honey orchestrates its mitigating effects, with the overarching objective of refining its application as an adjuvant natural product. Honey supplementation prevents AC toxicity via the inhibition of oxidative stress, NF-κB-mediated inflammation, and caspase-dependent apoptosis cascades. Although there is a need for increased mechanistic studies, honey is a natural product that could mitigate the various toxicities induced by AC.

The Potential of Fish Oil Components and Manuka Honey in Tackling Chronic Wound Treatment

Chronic wounds are becoming an increasing burden on healthcare services, as they have extended healing times and are susceptible to infection, with many failing to heal, which can lead ultimately to amputation. Due to the additional rise in antimicrobial resistance and emergence of difficult-to-treat Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. (ESKAPE pathogens), novel treatments will soon be required asides from traditional antibiotics. Many natural substances have been identified as having the potential to aid in both preventing infection and increasing the speed of wound closure processes. Manuka honey is already in some cases used as a topical treatment in the form of ointments, which in conjunction with dressings and fish skin grafts are an existing US Food and Drug Administration-approved treatment option. These existing treatment options indicate that fatty acids from fish oil and manuka honey are well tolerated by the body, and if the active components of the treatments were better understood, they could make valuable additions to topical treatment options. This review considers two prominent natural substances with established manufacturing and global distribution-marine based fatty acids (including their metabolites) and manuka honey-their function as antimicrobials and how they can aid in wound repair, two important aspects leading to resolution of chronic wounds.

Long-term stability and the physical and chemical factors predictive for antimicrobial activity in Australian honey

The growing burden of expired medicines contributes to environmental contamination and landfill waste accumulation. Medicinal honey, with its non-toxic nature and potentially long shelf-life, represents a promising and underutilised therapeutic that avoids some of these issues. However, limited knowledge on how its antimicrobial properties change over time combined with a lack of reliable processes in the honey industry for measuring antimicrobial potential, hinder its clinical adoption. Using a diverse selection of 30 Australian honey samples collected between 2005 and 2007, we comprehensively evaluated their antibacterial and antifungal activity and pertinent physical and chemical properties with the aims of assessing the effect of long-term storage on activity, pinpointing factors associated with antimicrobial efficacy, and establishing robust assessment methods. Minimum inhibitory concentration (MIC) assays proved superior to the standard phenol equivalence assay in capturing the full range of antimicrobial activity present in honey. Correlations between activity and a range of physical and chemical properties uncovered significant associations, with hydrogen peroxide, antioxidant content, and water activity emerging as key indicators in non-Leptospermum honey. However, the complex nature and the diverse composition of honey samples precludes the use of high-throughput chemical tests for accurately assessing this activity, and direct assessment using live microorganisms remains the most economical and reliable method. We provide recommendations for different methods of assaying various honey properties, taking into account their accuracy along with technical difficulty and safety considerations. All Leptospermum and fourteen of seventeen non-Leptospermum honey samples retained at least some antimicrobial properties after 15-17 years of storage, suggesting that honey can remain active for extended periods. Overall, the results of this study will help industry meet the growing demand for high-quality, medicinally active honey while ensuring accurate assessment of its antimicrobial potential.

Biochemical Profiling and Physicochemical and Biological Valorization of Iraqi Honey: A Comprehensive Analysis

Our study aimed to analyze five monovarietal honeys from the Salah Eddine region in Iraq, focusing on physicochemical, antioxidant, and antimicrobial properties and polyphenolic compounds. Our objective was to evaluate the strengths and qualities of Iraqi honeys, ensuring compliance with the Codex Alimentarius standard for honey. The spectrophotometric analysis included assessments of reduced sugar (75.8-77.7%), fructose-to-glucose ratio (0.7-0.9%), sucrose (2.2-2.9%), HMF (17.23-18.87 mg/kg), and melanoidin content (0.25-0.44), which were all determined. The electrical conductivity (0.39-0.46 mS/cm) using a conductivity meter, pH (4.02-4.31), and mineral composition were determined in all samples using atomic absorption spectrometry. Antioxidant activities were spectrophotometrically determined, through DPPH free radical scavenging (7.87-95.62 mg/mL), as was the total antioxidant activity (14.26-22.15 mg AAE/g), with correlations established with biochemical constituents such as the total phenol content, highlighting the significant presence of Coumaric acid (0.38-2.34 µg/mL), Catechin (1.80-2.68 µg/mL), and Quercetin (0.30 µg/mL) using HPLC. The study also observed notable antimicrobial activities using Escherichia coli, Staphylococcus aureus, and Candida albicans on Mueller-Hinton agar as well as through diffusion technique. In conclusion, our findings, including the antioxidant and antimicrobial strengths, underscore the substantial potential of Iraqi honeys in mitigating damage and preventing the onset of various diseases, affirming their good quality and adherence to international honey standards.

Bioactivities and Phenolic Profiles of Honeys Derived from Plants of the Goldfields, Esperance and Wheatbelt Regions of Western Australia

The aim of this study was to examine a collection of 79 honeys derived from plants endemic to several Western Australian unique bioregions for bioactivity and physicochemical characteristics. For physicochemical analyses, total phenolic content, high performance thin layer chromatography (HPTLC) fingerprints, pH, Brix, colour and hydrogen peroxide generation were examined. Brix (82.6±1.3) and pH (4.34±0.24) values were within expected ranges, whereas hydrogen peroxide levels determined using an o-dianisidine/horseradish peroxidase assay were relatively low, ranging from 0-244 μM. Antibacterial activity determined by the broth microdilution assay showed that Moort (Eucalyptus platypus) and Yate (Eucalyptus occidentalis) honeys had the highest overall activity with mean minimum inhibitory concentrations of 24.8 % and 25.1 % (w/v) honey, respectively. Yate honey also had the highest overall antioxidant activity (4.38±0.58 mmol Fe2+ /kg of honey), followed by Mallee honeys from various eucalypts, as determined by FRAP (Ferric reducing antioxidant power) and DPPH⋅ (2,2-Diphenyl-1-picrylhydrazyl) assays. This study identified new sources of honeys with potentially useful therapeutic properties from bioregions within Western Australia.

Low Levels of Hive Stress Are Associated with Decreased Honey Activity and Changes to the Gut Microbiome of Resident Honey Bees

Honey bees (Apis mellifera) face increasing threats to their health, particularly from the degradation of floral resources and chronic pesticide exposure. The properties of honey and the bee gut microbiome are known to both affect and be affected by bee health. Using samples from healthy hives and hives showing signs of stress from a single apiary with access to the same floral resources, we profiled the antimicrobial activity and chemical properties of honey and determined the bacterial and fungal microbiome of the bee gut and the hive environment. We found honey from healthy hives was significantly more active than honey from stressed hives, with increased phenolics and antioxidant content linked to higher antimicrobial activity. The bacterial microbiome was more diverse in stressed hives, suggesting they may have less capacity to exclude potential pathogens. Finally, bees from healthy and stressed hives had significant differences in core and opportunistically pathogenic taxa in gut samples. Our results emphasize the need for understanding and proactively managing bee health. IMPORTANCE Honey bees serve as pollinators for many plants and crops worldwide and produce valuable hive products such as honey and wax. Various sources of stress can disrupt honey bee colonies, affecting their health and productivity. Growing evidence suggests that honey is vitally important to hive functioning and overall health. In this study, we determined the antimicrobial activity and chemical properties of honey from healthy hives and hives showing signs of stress, finding that honey from healthy hives was significantly more antimicrobial, with increased phenolics and antioxidant content. We next profiled the bacterial and fungal microbiome of the bee gut and the hive environment, finding significant differences between healthy and stressed hives. Our results underscore the need for greater understanding in this area, as we found even apparently minor stress can have implications for overall hive fitness as well as the economic potential of hive products.

Unique antimicrobial activity in honey from the Australian honeypot ant (Camponotus inflatus)

Honey produced by the Australian honeypot ant (Camponotus inflatus) is valued nutritionally and medicinally by Indigenous peoples, but its antimicrobial activity has never been formally studied. Here, we determine the activity of honeypot ant honey (HPAH) against a panel of bacterial and fungal pathogens, investigate its chemical properties, and profile the bacterial and fungal microbiome of the honeypot ant for the first time. We found HPAH to have strong total activity against Staphylococcus aureus but not against other bacteria, and strong non-peroxide activity against Cryptococcus and Aspergillus sp. When compared with therapeutic-grade jarrah and manuka honey produced by honey bees, we found HPAH to have a markedly different antimicrobial activity and chemical properties, suggesting HPAH has a unique mode of antimicrobial action. We found the bacterial microbiome of honeypot ants to be dominated by the known endosymbiont genus Candidatus Blochmannia (99.75%), and the fungal microbiome to be dominated by the plant-associated genus Neocelosporium (92.77%). This study demonstrates that HPAH has unique antimicrobial characteristics that validate its therapeutic use by Indigenous peoples and may provide a lead for the discovery of novel antimicrobial compounds.

Honey-Related Treatment Strategies in Dry Eye Disease

This systematic review and meta-analysis investigated whether honey-related treatment strategies improve the signs and symptoms of patients with dry eye disease (DED). In March 2023, the following databases were accessed for clinical trials investigating the efficacy of honey-related treatment strategies in DED: PubMed, Web of Science, Google Scholar, and EMBASE. The following data were extracted at baseline and at the last follow-up: Ocular Surface Disease Index, tear breakup time, Schirmer I test, and corneal staining. Data from 323 patients were retrieved (53.3% female, mean age 40.6 ± 18.1 years). The mean follow-up was 7.0 ± 4.2 weeks. All the endpoints of interest significantly improved from baseline to the last follow-up: tear breakup time (p = 0.01), Ocular Surface Disease Index (p < 0.0001), Schirmer I test (p = 0.0001), and corneal staining (p < 0.0001). No difference was found in tear breakup time (p = 0.3), Ocular Surface Disease Index (p = 0.4), Schirmer I test (p = 0.3), and corneal staining (p = 0.3) between the honey-related treatment strategies and the control groups. According to our main results, honey-related treatment strategies are effective and feasible to improve symptoms and signs of DED.

Design, Preparation, and Physicochemical Characterisation of Alginate-Based Honey-Loaded Topical Formulations

Honey has widespread use as a nutritional supplement and flavouring agent. Its diverse bioactivities, including antioxidant, antimicrobial, antidiabetic, anti-inflammatory, and anticancer properties, have also made it an aspirant natural product for therapeutic applications. Honey is highly viscous and very sticky, and its acceptance as a medicinal product will require formulation into products that are not only effective but also convenient for consumers to use. This study presents the design, preparation, and physicochemical characterisation of three types of alginate-based topical formulations incorporating a honey. The honeys applied were from Western Australia, comprising a Jarrah honey, two types of Manuka honeys, and a Coastal Peppermint honey. A New Zealand Manuka honey served as comparator honey. The three formulations were a pre-gel solution consisting of 2-3% (w/v) sodium alginate solution with 70% (w/v) honey, as well as a wet sheet and a dry sheet. The latter two formulations were obtained by further processing the respective pre-gel solutions. Physical properties of the different honey-loaded pre-gel solutions (i.e., pH, colour profile, moisture content, spreadability, and viscosity), wet sheets (i.e., dimension, morphology, and tensile strength) and dry sheets (i.e., dimension, morphology, tensile strength, and swelling index) were determined. High-Performance Thin-Layer Chromatography was applied to analyse selected non-sugar honey constituents to assess the impacts of formulation on the honey chemical composition. This study demonstrates that, irrespective of the honey type utilised, the developed manufacturing techniques yielded topical formulations with high honey content while preserving the integrity of the honey constituents. A storage stability study was conducted on formulations containing the WA Jarrah or Manuka 2 honey. The samples, appropriately packaged and stored over 6 months at 5, 30, and 40 °C, were shown to retain all physical characteristics with no loss of integrity of the monitored honey constituents.

Monitoring the Release of Methylglyoxal (MGO) from Honey and Honey-Based Formulations

Methylglyoxal (MGO) is considered to be one of the vital components responsible for the anti-bacterial activity of Leptospermum spp. (Manuka) honey. While many studies have demonstrated a dose-dependent antibacterial activity for MGO in vitro, from a therapeutic viewpoint, it is also important to confirm its release from Manuka honey and also from Manuka honey-based formulations. This study is the first to report on the release profile of MGO from five commercial products containing Manuka honey using a Franz diffusion cell and High-Performance Liquid Chromatography (HPLC) analysis. The release of MGO expressed as percentage release of MGO content at baseline was monitored over a 12 h period and found to be 99.49 and 98.05% from an artificial honey matrix and NZ Manuka honey, respectively. For the investigated formulations, a time-dependent % MGO release between 85% and 97.18% was noted over the 12 h study period.

The Potential of Honey as a Prebiotic Food to Re-engineer the Gut Microbiome Toward a Healthy State

Honey has a long history of use for the treatment of digestive ailments. Certain honey types have well-established bioactive properties including antibacterial and anti-inflammatory activities. In addition, honey contains non-digestible carbohydrates in the form of oligosaccharides, and there is increasing evidence from in vitro, animal, and pilot human studies that some kinds of honey have prebiotic activity. Prebiotics are foods or compounds, such as non-digestible carbohydrates, that are used to promote specific, favorable changes in the composition and function of the gut microbiota. The gut microbiota plays a critical role in human health and well-being, with disturbances to the balance of these organisms linked to gut inflammation and the development and progression of numerous conditions, such as colon cancer, irritable bowel syndrome, obesity, and mental health issues. Consequently, there is increasing interest in manipulating the gut microbiota to a more favorable balance as a way of improving health by dietary means. Current research suggests that certain kinds of honey can reduce the presence of infection-causing bacteria in the gut including Salmonella, Escherichia coli, and Clostridiodes difficile, while simultaneously stimulating the growth of potentially beneficial species, such as Lactobacillus and Bifidobacteria. In this paper, we review the current and growing evidence that shows the prebiotic potential of honey to promote healthy gut function, regulate the microbial communities in the gut, and reduce infection and inflammation. We outline gaps in knowledge and explore the potential of honey as a viable option to promote or re-engineer a healthy gut microbiome.

Glucose Oxidase and Catalase Activities in Honey Samples from the Southwestern Region of Saudi Arabia

The activity of honey enzymes are affected by floral and geographical origins, climate conditions, honeybee species, health and nutrition. This article investigated the effect of floral and geographical origins on the activity of glucose oxidase (GOx) and catalase (CAT) enzymes in honey samples from the southwestern region of Saudi Arabia. Moreover, the moisture, total sugars, pH and conductivity were measured as quality parameters. The floral origin of the honey samples was determined microscopically while the quality parameters were measured according to the methods of international honey commission. The activity of the honey enzyme was determined following the instructions of the Megazyme International kits. The obtained results were statistically analyzed by the statistical Package for Social Sciences (SPSS, v.20). The GOx activity of the Acacia, Ziziphus and polyfloral honey samples of the Asir region were (5.19 ± 2.33 U/g), (4.01 ± 1.17 U/g) and (5.69 ± 1.67 U/g), respectively. The Acacia, Ziziphus and polyfloral honey samples from the Jazan region had GOx activities of (6.85 ± 0.47 U/g), (10.48 ± 9.22 U/g) and (5.31 ± 2.7 U/g), respectively. The geographical origin significantly affected the GOx activity of Ziziphus honey (p-value = 0.005) and the GOx activity of the Ziziphus honey was significantly more than that of the polyfloral honey of the Jazan region (p-value = 0.009). With regard to the CAT activity in Asir region honey samples, the mean values of the Acacia, Ziziphus and polyfloral honeys were (2.89 ± 1.08 U/g), (3.58 ± 1.59 U/g) and (2.84 ± 1.24 U/g), respectively. The mean values of the CAT activity in the Jazan honey samples were Acacia (4.35 ± 1.01 U/g), Ziziphus (3.94 ± 0.04 U/g) and polyfloral (3.43 ± 0.67 U/g). The geographical origin significantly affected the CAT activity in Acacia honey (p-value = 0.014). The geographical and floral origins had significant effects on the activity of the honey GOx and CAT enzymes.

In vitro antibacterial activity of Western Australian honeys, and manuka honey, against bacteria implicated in impetigo

Impetigo is a contagious skin disease caused by Staphylococcus aureus and Streptococcus pyogenes. Without treatment, impetigo may be recurrent, develop into severe disease, or have serious, life-threatening sequelae. Standard treatment consists of topical or systemic antibiotic therapy (depending on severity), however, due to antibiotic resistance some therapies are increasingly ineffective. In this study we evaluated the potential for honey as an alternative treatment for impetigo. A broth microdilution assay in 96-well microtitre trays was used to determine the minimum inhibitory concentrations (MICs) of six monofloral honeys (jarrah, marri, red bell, banksia, wandoo, and manuka), a multifloral honey and artificial honey against S. aureus (n = 10), S. pyogenes (n = 10), and coagulase-negative staphylococci (CoNS) (n = 10). The optical density (OD) of all microtitre tray wells was also determined before and after assay incubation to analyse whether sub-MIC growth inhibition occurred. Jarrah, marri, red bell, banksia, and manuka honeys were highly effective at inhibiting S. aureus and CoNS, with MIC₅₀ values ranging from 4 to 8% w/v honey. S. pyogenes was also inhibited by these same honeys, albeit at higher concentrations (8-29% w/v). Wandoo and multifloral honeys had the least antibacterial activity with MICs of >30% (w/v) for all isolates. However, OD data indicated that sub-MIC concentrations of honey were still partially restricting bacterial growth. Our pre-clinical data indicate that honey may be a potential therapeutic agent for the routine treatment of mild impetigo, and we suggest that clinical trials would be appropriate to further investigate this.

Efficacy of topical honey compared to systemic gentamicin for treatment of infected war wounds in a porcine model: A non-inferiority experimental pilot study

BACKGROUND

In armed conflicts, infected wounds constitute a large portion of the surgical workload. Treatment consists of debridements, change of dressings, and antibiotics. Many surgeons advocate for the use of honey as an adjunct with the rationale that honey has bactericidal and hyperosmotic properties. However, according to a Cochrane review from 2015 there is insufficient data to draw any conclusions regarding the efficacy of honey in treatment of wounds. We, therefore, decided to evaluate if honey is non-inferior to gentamicin in the treatment of infected wounds in a highly translatable porcine wound model.

MATERIAL AND METHODS

50 standardized wounds on two pigs were infected with S. aureus and separately treated with either topically applied Manuka honey or intramuscular gentamicin for eight days. Treatment efficacy was evaluated with quantitative cultures, wound area measurements, histological, immunohistochemical assays, and inflammatory response.

RESULTS

Topically applied Manuka honey did not reduce bacterial count or wound area for the duration of treatment. Intramuscular gentamicin initially reduced bacterial count (geometric mean 5.59*¸0.37 - 4.27*¸0.80 log10 (GSD) CFU/g), but this was not sustained for the duration of the treatment. However, wound area was significantly reduced with intramuscular gentamicin at the end of treatment (mean 112.8 ± 30.0-67.7 ± 13.2 (SD) mm2). ANOVA-analysis demonstrated no variation in bacterial count for the two treatments but significant variation in wound area (p<0.0001). The inflammatory response was more persistent in the pig with wounds treated with topically applied Manuka honey than in the pig treated with intramuscular gentamicin.

CONCLUSION

At the end of treatment S. aureus count was the same with topically applied Manuka honey and intramuscular gentamicin. The wound area was unchanged with topically applied Manuka honey and decreased with intramuscular gentamicin. Topically applied Manuka honey could consequently be non-inferior to intramuscular gentamicin in reducing S. aureus colonization on the wound's surface, but not in reducing wound size. The use of Manuka honey dressings to prevent further progression of a wound infection may therefore be of value in armed conflicts, where definite care is not immediately available.

Potential effects of Saudi Shaoka (Fagonia bruguieri) honey against multi-drug-resistant bacteria and cancer cells in comparison to Manuka honey

The global spread of antimicrobial-resistant infectious diseases and cancer are the most widespread public health issue and has led to high mortality rates. This study aims to evaluate and verify the antibacterial and antitumor activities of Shaoka and Manuka honey against pathogenic bacteria, human hepatocarcinoma (HepG2) and breast cancer (MCF-7) cell lines. Shaoka hone was analyzed using HPLC, UV–vis, and GC/MC, while antibacterial activity was measured by agar diffusion, broth microdilution methods, and Transmission Electron Microscopy (TEM). Antitumor activity was investigated morphologically and by MTT assay. According to the presented data of HPLC analysis, Shaoka honey was generally richer in polyphenolic components, the antibacterial activity showed that Shaoka honey is equivalent or relatively more active than Manuka honey against a broad spectrum of multi-drug-resistant bacteria. It inhibited the growth of ESBL Escherichia coli in the absence or presence of catalase enzyme with a concentration approximately 8.5%–7.3% equivalent to phenol, which supported the highest level of non-peroxide-dependent activity. The minimum bactericidal concentrations (MBCs) ranged between 5.0% and 15.0% honey (w/v). TEM observation revealed distorted cell morphology, cytoplasmic shrinkage, and cell wall destruction of treated bacteria. The selected honey exerted cytotoxicity on both cancer cell lines, inhibiting cell proliferation rate and viability percent in HepG2 and MCF-7 cancer cells, by different degrees depending on the honey quality, Shaoka honey competed Manuka inhibitory effects against both cancer cells. The obtained data confirmed the potential for use of Saudi Shaoka honey as a remedy, this well introduces a new honey template as medical-grade honey for treating infectious disease and cancer.

The investigation of biochemical and microbiological properties of four different honey types produced in turkey and the comparison of their effects with silver sulfadiazine on wound healing in a rat model of burn injury

Background

To determine and compare the effects of different honey types on wound healing in an animal model, with silver sulfadiazine as the standard treatment.

Materials and Methods

Five different groups were created with eight rats in each group. Partial-depth burns were created, and different types of honey and silver sulfadiazine were applied to the respective groups. Rats were monitored for 21 days, and wound cultures were obtained. Histopathological evaluation and cytokine analysis of final tissue samples were performed. In addition, the biochemical and microbiological analyses of the four types of honey used in the study were performed.

Results

Wound shrinkage comparisons showed that all four honey-treated groups (Bingöl, Konya, cotton, and citrus) performed better than the silver sulfadiazine group (honey groups, respectively, 86.86%, 84.72%, 89.61%, and 95.33% vs. control 82.90%). However, only citrus honey caused a significant difference in wound shrinkage rate when compared with other groups as well with control group (95.34% vs. 82.9%, P < 0.05). In tissues, all honey groups had higher cytokine (interleukin [IL]-6, IL-1B, tumor necrosis factor [TNF]-α) values compared with controls (P < 0.001). Honey analysis showed a significant inverse relationship between Fe (iron) and the number of diastases.

Conclusions

The results of this study support the role of honey in wound healing, due to its antibacterial and immunomodulatory effects. More studies are needed to identify the role of honey composition in wound healing.

Cataloguing the small RNA content of honey using next generation sequencing

•

Plant miRNAs are present in Australian polyfloral and Leptospermum scoparium honey.

•

Sequencing shows that honey contains a diverse range of small, non-coding RNAs.

•

Honey RNA comes from different phylogenies including invertebrates and prokaryotes.

•

Unique small RNA profiles can provide insight into honey production conditions.

Honey adulteration is a problem that effects the global honey industry and specifically, has been discovered in the Australian market. Common methods of adulteration include dilution with sugar syrup substitutes and the mislabelling of the floral and geographic origin(s) of honey. Current authentication tools rely on the molecular variability between different honeys, identifying unique chemical profiles and/or DNA signatures characteristic of a particular honey.

Honey is known to contain plant miRNAs derived from its floral source. To explore the composition and variability of honey RNA molecules, this is the first study to catalogue the small RNA content of Australian polyfloral table honey and New Zealand Leptospermum scoparium honey using next generation sequencing. The data shows that in addition to miRNAs, honey contains a variety of small non-coding RNAs including tRNA-derived fragments. Moreover, the honey small RNAs are derived from a range of phylogenetic sources, including from plant, invertebrate, and prokaryotic species. The data indicates that different honeys contain unique small RNA profiles, which suggests a novel avenue in developing molecular-based honey authentication tools.

Bee Pollen and Bee Bread as a Source of Bacteria Producing Antimicrobials

The principal objective of the study was the isolation and identification of bacteria that are present in mature bee bread (BB) and dried (ready for selling and consumption) bee pollen (BP). Obtained isolates were screened for their potential to inhibit select human pathogenic bacteria and their ability to produce enzymes of particular industrial importance. Four and five samples of BP and BB, respectively, were used for the study. In total, 81 strains of bacteria were isolated, and 34 (42%) of them exhibited antagonistic interactions with at least one reference strain of pathogenic bacteria, namely Staphylococcus aureus ATCC 25923, Staphylococcus aureus ATCC 29213, Staphylococcus epidermidis 12228, Pseudomonas aeruginosa ATCC 27857, and Escherichia coli ATCC 25922. The sequencing of the 16S rRNA gene revealed that all strains producing antimicrobials belong to the genus Bacillus spp., and among them, five species were identified: B. pumilus (n = 17), B. altitudinis (n = 9), B. licheniformis (n = 4), B. subtilis (n = 2), and B. safensis (n = 1). Furthermore, 69, 54, 39, and 29 of the strains exhibited lipolytic, proteolytic, cellulolytic, and esterolytic activity, respectively. Alpha amylase and beta galactosidase activity were rarely observed, and none of the strains produced laccase. The outcomes of the study revealed that BP and BB can be considered potential sources of bacteria producing antimicrobial agents and/or enzymes of particular industrial importance. Of course, additional research is required to verify this hypothesis, but the results of preliminary studies are promising.

Evolution of honey resistance in experimental populations of bacteria depends on the type of honey and has no major side effects for antibiotic susceptibility

With rising antibiotic resistance, alternative treatments for communicable diseases are increasingly relevant. One possible alternative for some types of infections is honey, used in wound care since before 2000 BCE and more recently in licensed, medical-grade products. However, it is unclear whether medical application of honey results in the evolution of bacterial honey resistance and whether this has collateral effects on other bacterial traits such as antibiotic resistance. Here, we used single-step screening assays and serial transfer at increasing concentrations to isolate honey-resistant mutants of Escherichia coli. We only detected bacteria with consistently increased resistance to the honey they evolved in for two of the four tested honey products, and the observed increases were small (maximum twofold increase in IC90). Genomic sequencing and experiments with single-gene knockouts showed a key mechanism by which bacteria increased their honey resistance was by mutating genes involved in detoxifying methylglyoxal, which contributes to the antibacterial activity of Leptospermum honeys. Crucially, we found no evidence that honey adaptation conferred cross-resistance or collateral sensitivity against nine antibiotics from six different classes. These results reveal constraints on bacterial adaptation to different types of honey, improving our ability to predict downstream consequences of wider honey application in medicine.

Quantification of Hydrogen Peroxide in Cretan Honey and Correlation with Physicochemical Parameters

The aim of the present study is to quantify hydrogen peroxide, generated from various types of honey produced in Crete, as a potent antimicrobial agent, and establish any correlation with their physicochemical parameters. The basic physicochemical parameters (diastase activity, HMF content, moisture, electrical conductivity, color, and sugars) of 30 authentic honey samples were determined. The concentration of hydrogen peroxide in all samples was found to be within the range 0.010-0.092 mM. The known correlation between the electrical conductivity and the color of honey was confirmed in this study. Univariate and multivariate statistics applied to the results indicate that the results can be used to discriminate honey sample groups of different botanical origins.

Inhibition of Dermatophyte Fungi by Australian Jarrah Honey

Superficial dermatophyte infections, commonly known as tineas, are the most prevalent fungal ailment and are increasing in incidence, leading to an interest in alternative treatments. Many floral honeys possess antimicrobial activity due to high sugar, low pH, and the production of hydrogen peroxide (H2O2) from the activity of the bee-derived enzyme glucose oxidase. Australian jarrah (Eucalyptus marginata) honey produces particularly high levels of H2O2 and has been found to be potently antifungal. This study characterized the activity of jarrah honey on fungal dermatophyte species. Jarrah honey inhibited dermatophytes with minimum inhibitory concentrations (MICs) of 1.5-3.5% (w/v), which increased to ≥25% (w/v) when catalase was added. Microscopic analysis found jarrah honey inhibited the germination of Trichophyton rubrum conidia and scanning electron microscopy of mature T. rubrum hyphae after honey treatment revealed bulging and collapsed regions. When treated hyphae were stained using REDOX fluorophores these did not detect any internal oxidative stress, suggesting jarrah honey acts largely on the hyphal surface. Although H2O2 appears critical for the antifungal activity of jarrah honey and its action on fungal cells, these effects persisted when H2O2 was eliminated and could not be replicated using synthetic honey spiked with H2O2, indicating jarrah honey contains agents that augment antifungal activity.

Factors affecting the production and measurement of hydrogen peroxide in honey samples

Many Australian native honeys possess significant antimicrobial properties due to the production of hydrogen peroxide (H₂O₂) by glucose oxidase, an enzyme derived from the honeybee. The level of H₂O₂ produced in different honey samples is highly variable, and factors governing its production and stability are not well understood. In this study, highly active Australian honeys that had been stored for >10 years lost up to 54 % of their antibacterial activity, although almost all retained sufficient activity to be considered potentially therapeutically useful. We used a simple colourimetric assay to quantify H₂O₂ production. Although we found a significant correlation between H₂O₂ production and antibacterial activity across diverse honey samples, variation in H₂O₂ only explained 47 % of the variation observed in activity, limiting the assay as a screening tool and highlighting the complexity of the relationship between H₂O₂ and the killing power of honey. To further examine this, we tested whether H₂O₂ detection in honey was being inhibited by pigmented compounds and if H₂O₂ might be directly degraded in some honey samples. We found no correlation between H₂O₂ detection and honey colour. Some honey samples rapidly lost endogenous and spiked H₂O₂, suggesting that components in honey, such as catalase or antioxidant polyphenols, may degrade or quench H₂O₂. Despite this rapid loss of H₂O₂, these honeys had significant peroxide-based antibacterial activity, indicating a complex relationship between H₂O₂ and other honey components that may act synergistically to augment activity.

Development and validation of a new microplate assay that utilises optical density to quantify the antibacterial activity of honeys including Jarrah, Marri and Manuka

The phenol equivalence assay is the current industry-adopted test used to quantify the antibacterial activity of honeys in Australia and New Zealand. Activity is measured based on the diffusion of honey through agar and resulting zone of growth inhibition. Due to differences in the aqueous solubilities of antibacterial compounds found in honeys, this method may not be optimal for quantifying activity. Therefore, a new method was developed based on the existing broth microdilution assay that is widely used for determining minimum inhibitory concentrations (MICs). It utilises the four organisms Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853, and an optical density endpoint to quantify bacterial growth. Decreases in bacterial growth in the presence of honey, relative to the positive growth control, are then used to derive a single value to represent the overall antibacterial activity of each honey. Antibacterial activity was quantified for a total of 77 honeys using the new method, the phenol equivalence assay and the standard broth microdilution assay. This included 69 honeys with undisclosed floral sources and the comparators Manuka, Jarrah (Eucalyptus marginata), Marri (Corymbia calophylla), artificial and multifloral honey. For the 69 honey samples, phenol equivalence values ranged from 0-48.5 with a mean of 34 (% w/v phenol). Mean MICs, determined as the average of the MICs obtained for each of the four organisms for each honey ranged from 7-24% (w/v honey). Using the new assay, values for the 69 honeys ranged from 368 to 669 activity units, with a mean of 596. These new antibacterial activity values correlated closely with mean MICs (R2 = 0.949) whereas the relationship with phenol equivalence values was weaker (R2 = 0.649). Limit of detection, limit of quantitation, measuring interval, limit of reporting, sensitivity, selectivity, repeatability, reproducibility, and ruggedness were also investigated and showed that the new assay was both robust and reproducible.

Honey Combination Therapies for Skin and Wound Infections: A Systematic Review of the Literature

Topical application of medical grade honey is recommended for the clinical management of wound infections. The suitability of honey as a wound healing agent is largely due to its antibacterial activity, immune modulatory properties, and biocompatibility. Despite the usefulness of honey in wound healing, chronic wound infections continue to be a global problem requiring new and improved therapeutic interventions. Several recent studies have investigated the effects of combining honey with other therapies or agents with the aim of finding more efficacious treatments. In this systematic review, the database PubMed was used to carry out a search of the scientific literature on the combined effects of honey and other therapies on antimicrobial activity and wound and skin healing. The search revealed that synergistic or additive antimicrobial effects were observed in vitro when honey was combined with antibiotics, bacteriophages, antimicrobial peptides, natural agents, eg, ginger or propolis and other treatment approaches such as the use of chitosan hydrogel. Outcomes depended on the type of honey, the combining agent or treatment and the microbial species or strain. Improved wound healing was also observed in vivo in mice when honey was combined with laser therapy or bacteriophage therapy. More clinical studies in humans are required to fully understand the effectiveness of honey combination therapies for the treatment of skin and wound infections.

Antibacterial properties of selected Malaysian Tualang honey against Pseudomonas aeruginosa and Streptococcus pyogenes

BACKGROUND AND OBJECTIVES

Tualang honey (TH) is a Malaysian multifloral jungle honey. In recent years, there has been a marked increase in the number of studies published in medical databases regarding its potential health benefits. The study aimed to investigate the effect of TH against Pseudomonas aeruginosa and Streptococcus pyogenes.

MATERIALS AND METHODS

The effect of TH on both bacteria was investigated using MIC, MBC, growth curve, time-kill curve, scanning electron microscopy (SEM) and RT-qPCR.

RESULTS

The MIC of TH against P. aeruginosa and S. pyogenes was 18.5% (w/v) and 13% (w/v) respectively and MBC was 25% (w/v) for both bacteria. Spectrophotometric readings of at least 90% inhibition yielded MIC90 values of TH, 18.5% (w/v) and 15% (w/v) for P. aeruginosa and S. pyogenes respectively. A time-kill curve demonstrated a bactericidal with a 4-log reduction estimated within 8 hours. Using SEM, loss of structural integrity and marked changes in cell shape were observed. RT-qPCR analysis showed that TH reduced the pattern of gene expression in both bacteria, with a trend toward reduced expression of the virulence genes of interest.

CONCLUSION

This study suggests that TH could potentially be used as an alternative therapeutic agent for microbial infection particularly against these two organisms.

Gut microbiota is involved in the alleviation of loperamide-induced constipation by honey supplementation in mice

Constipation is one of the most common functional gastrointestinal disorders accompanied with intestinal dysbiosis. Laxatives for constipation usually have side effects. Bee honey is a natural food with unique composition, antimicrobial properties, and bifidogenic effect. In order to assess whether honey can ameliorate loperamide-induced constipation in BALB/c mice through the alteration of the gut microbiota, the present study was undertaken. Mice were given Jarrah honey (7.5 g/kg body weight) by gavage once per day for 5 days. Fecal water content, intestinal transit rate together with the colon concentrations of substance P (SP), vasoactive intestinal peptide (VIP), and serotonin (5-hydroxytryptamine; 5-HT) were evaluated. Furthermore, we determined the effect of honey treatment on gut microbiota in mice using stool genomic 16S rRNA sequencing. As a result, honey showed an obvious improvement in fecal water content and alleviated constipation by modulating the microbial composition of the microbiota, and this was highly associated with a proportional decrease in gut Desulfovibrio. In addition, we found that the colon level of neurotransmitters SP and VIP was significantly related to microbial variations. Our results indicate that gut microbiota is involved in the alleviation of loperamide-induced constipation by honey supplementation in mice, and it could be considered as an evaluating parameter in constipation therapy strategies.

Characterizing the Mechanism of Action of an Ancient Antimicrobial, Manuka Honey, against Pseudomonas aeruginosa Using Modern Transcriptomics

Manuka honey has broad-spectrum antimicrobial activity, and unlike traditional antibiotics, resistance to its killing effects has not been reported. However, its mechanism of action remains unclear. Here, we investigated the mechanism of action of manuka honey and its key antibacterial components using a transcriptomic approach in a model organism, Pseudomonas aeruginosa We show that no single component of honey can account for its total antimicrobial action, and that honey affects the expression of genes in the SOS response, oxidative damage, and quorum sensing. Manuka honey uniquely affects genes involved in the explosive cell lysis process and in maintaining the electron transport chain, causing protons to leak across membranes and collapsing the proton motive force, and it induces membrane depolarization and permeabilization in P. aeruginosa These data indicate that the activity of manuka honey comes from multiple mechanisms of action that do not engender bacterial resistance.IMPORTANCE The threat of antimicrobial resistance to human health has prompted interest in complex, natural products with antimicrobial activity. Honey has been an effective topical wound treatment throughout history, predominantly due to its broad-spectrum antimicrobial activity. Unlike traditional antibiotics, honey-resistant bacteria have not been reported; however, honey remains underutilized in the clinic in part due to a lack of understanding of its mechanism of action. Here, we demonstrate that honey affects multiple processes in bacteria, and this is not explained by its major antibacterial components. Honey also uniquely affects bacterial membranes, and this can be exploited for combination therapy with antibiotics that are otherwise ineffective on their own. We argue that honey should be included as part of the current array of wound treatments due to its effective antibacterial activity that does not promote resistance in bacteria.

Physico-chemical, antioxidant and anti-microbial properties of some Ethiopian mono-floral honeys

Honey has been widely used to treat several human pathogens. However, all honeys may not have equal potencies against different human pathogens. The purpose of the current work was to investigate the physico-chemical and antimicrobial qualities of some mono-floral honeys from Ethiopia against some human pathogen bacteria and fungi. In the study, seven different botanical origin honeys were used of which some were from plants known for their medicinal properties. The samples were tested for their major physico-chemical properties (sugar profiles, total free acids, pH, color, electric conductivity and total soluble substances) and their medicinal values as total antioxidant capacity, total phenolic content and antimicrobial properties as minimum inhibitory concentration against some human pathogens, following standard protocols. Generally, the average values of the physico-chemical properties of the samples were within the acceptable ranges of world honey quality values. The average total antioxidant value of the samples was 320.3 ± 15.1 with range of 225.4 ± 12.8-465.7 ± 21.8 μM Fe(II)/100g. Relatively higher values 421.5 ± 23.4 and 465.7 ± 21.8μM Fe(II)/100g recorded for Croton macrostachyus and Vernonia amygalina honeys respectively. The average phenolic contents of the samples varied from 233.3 ± 24.0 to 693.3 ± 26.8 mgGAE/kg and relatively higher values recorded for C. macrostachys and V. amygdalina honeys. The significant proportion of the tested samples showed strong antimicrobial qualities inhibiting the growth of tested pathogens at concentration of 10.5%-28.6% of MIC (% v/v). Honeys from medicinal plants (C. macrostachys and V. amygdalina) relatively showed more antimicrobial properties which could be due to the presence of plant specific phytochemicals which require further investigations.

Physical characteristics and antimicrobial properties of Apis mellifera, Frieseomelitta nigra and Melipona favosa bee honeys from apiaries in Trinidad and Tobago

Background

Honey is a versatile and complex substance consisting of bioactive chemicals which vary according to many bee and environmental factors. The aim of this study was to assess the physical and antimicrobial properties of five honey samples obtained from three species of bees; two stingless bees, Frieseomelitta nigra and Melipona favosa and one stinging bee, Apis mellifera (fresh and aged honey). Samples were acquired from apiaries across Trinidad and Tobago. An artificial honey, made from sugar, was also used for comparison.

Methods

Physical properties such as appearance, pH, moisture content, sugar content and specific gravity were determined. Antimicrobial activity was assessed utilizing the agar diffusion assay and comparison to a phenol equivalence. The broth microdilution test was performed to determine the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of the five honey samples against four common pathogens, including Staphylococcus aureus, Escherichia coli, Streptococcus pyogenes and Haemophilus influenzae.

Results

All honey samples were acidic, with pH values ranging from 2.88 (M. favosa of Tobago) to 3.91 (fresh A. mellifera). Sugar content ranged from 66.0 to 81.6% with the highest values detected in stinging bee honeys of the A. mellifera (81.6 and 80.5°Bx). Moisture content ranged from 16.9% for aged A. mellifera honey (from Trinidad) to 32.4% for F. nigra honey (from Tobago). The MICs (2 to 16%) and MBCs (2 to 32%) of stingless bee honeys were lower than that of stinging bee and artificial honeys (16 to > 32%). Stingless bee honeys also exhibited a broad spectrum of antimicrobial activity against both Gram-positive and Gram-negative organisms with higher phenol equivalence values (4.5 to 28.6%) than the A. mellifera honeys (0 to 3.4%) against the isolates tested. M. favosa honey of Tobago displayed the greatest antimicrobial activity as indicated by the high phenol equivalence and low MIC and MBC values.

Conclusions

Stingless bee honeys from Tobago showed the greatest antimicrobial activity when compared to the other honeys used in this study. M. favosa honey of Tobago showed the most potential for use as medicinal honey.

Antibiotics, Acid and Heat Tolerance of Honey adapted Escherichia coli, Salmonella Typhi and Klebsiella pneumoniae

The medicinal importance of honey has been known for many decades due to its antimicrobial properties against life-threatening bacteria. However, previous studies revealed that microorganisms are able to develop adaptations after continuous exposure to antimicrobial compounds. The present study was conducted to explore the impact of subinhibitory concentrations of branded honey (Marhaba) and unbranded honey (extracted from Ziziphus mauritiana plant) locally available in Pakistan on Escherichia coli ATCC 10536, Salmonella Typhi and Klebsiella pneumoniae by investigating the development of self- or cross-resistance to antibiotics (gentamicin, kanamycin and imipenem). Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of autoclaved honeys were determined. The bacterial cells of E. coli ATCC 10536, S. Typhi and K. pneumoniae were subjected to honey adaptation by exposing to ¼ × MIC (4 passages) and ½ × MIC (4 passages) of both honeys. Moreover, tolerance to low pH and high temperature was also studied in adapted and unadapted cells. The decreasing trend in growth pattern (OD_600nm) of E. coli ATCC 10536, S. Typhi and K. pneumoniae was observed with increases in the concentration of honeys (6.25–50% v/v) respectively. Our results showed that continuous exposure of both honeys did not lead to the development of any self- or cross-resistance in tested bacteria. However, percent survival to low pH was found to be significantly higher in adapted cells as compared to unadapted cells. The results indicate that both branded honey (Marhaba) and unbranded honey (extracted from Ziziphus mauritiana plant) were effective in controlling the growth of tested pathogenic bacteria. However, the emergence of tolerance to adverse conditions (pH 2.5, temperature 60 °C) deserves further investigation before proposing honey as a better antibacterial agent in food fabrication/processing, where low pH and high temperatures are usually implemented.

In vitro antimicrobial activities of Saudi honeys originating from Ziziphus spina-christi L. and Acacia gerrardii Benth. trees

Honeys originating from Sidr (Ziziphus spina-christi L.) and Talh (Acacia gerrardii Benth.) trees in Saudi Arabia exhibited substantial antimicrobial activity against pathogenic gram-positive bacteria (Bacillus cereus, Staphylococcus aureus), gram-negative bacteria (Escherichia coli, Salmonella enteritidis), and a dermatophytic fungus (Trichophyton mentagrophytes). The diameter of zones of inhibition represents the level of antimicrobial potency of the honey samples. Precisely, Talh honey showed significantly higher antibacterial activity against all tested bacteria than Sidr honey. The antifungal activity of Talh and Sidr honey types was significantly at par against a dermatophytic fungus. The water-diluted honey types (33% w/v) significantly induced a rise in the antimicrobial activity from that of the natural nondiluted honeys. Microbial strains displayed differential sensitivity; gram-positive bacteria were more sensitive and presented larger inhibition zones than gram-negative bacteria and the fungus. The sensitivity was highest in B. cereus and S. aureus, followed by T. mentagrophytes, E. coli, and S. enteritidis. The antimicrobial activity of water-diluted honeys (Sidr and Talh) was high than that of broad-spectrum antibacterial antibiotics (tetracycline and chloramphenicol) against bacterial strains, but these honeys were relativity less potent than antifungal antibiotics (flucoral and mycosat) against a fungal strain. Our findings indicate the antimicrobial potential of Saudi honeys to be considered in honey standards, and their therapeutic use as medical-grade honeys needs further investigations.

Manuka honey chelates iron and impacts iron regulation in key bacterial pathogens

AIM

The aim of this study was to test the hypothesis that Manuka honey (MH) chelates iron and promotes an iron-limiting environment, which contributes to its antimicrobial activity.

METHODS AND RESULTS

Employing a ferrozine-based assay, we observed that MH is an iron chelator that depletes iron from solution. Siderophores are small molecules that bind ferric iron (III) with high affinity and their levels are upregulated by bacteria under iron-limiting conditions. We demonstrated by quantitating siderophore production that Escherichia coli and Pseudomonas aeruginosa treated with MH sub-minimum inhibitory concentrations (sub-MIC) experience an iron-limiting environment and increase siderophore production. In addition, supplementation with ferrous iron (II) significantly increased growth of E. coli, Staphylococcus aureus and P. aeruginosa cultured at their MH MIC above that observed in nonsupplemented controls. By contrast, supplementation with ferric iron (III) significantly increased growth for only E. coli and P. aeruginosa, above their nonsupplemented controls.

CONCLUSIONS

Manuka honey chelates iron, thereby generating an iron-limiting environment for E. coli and P. aeruginosa, and to a lesser extent S. aureus, which contributes to its antimicrobial properties.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our work demonstrates that MH-induced iron chelation is an antimicrobial mechanism that differentially impacts the bacterial species tested here. Iron chelation affects multiple diverse physiological processes in bacteria and would contribute to the lack of bacterial resistance to MH. Iron metabolism is tightly regulated; bacteria require this essential nutrient for survival, but in excess it is toxic. Additional exploration of MH's iron chelation mechanism will facilitate its future use in mainstream medicine.

Honey can inhibit and eliminate biofilms produced by Pseudomonas aeruginosa

Chronic wound treatment is becoming increasingly difficult and costly, further exacerbated when wounds become infected. Bacterial biofilms cause most chronic wound infections and are notoriously resistant to antibiotic treatments. The need for new approaches to combat polymicrobial biofilms in chronic wounds combined with the growing antimicrobial resistance crisis means that honey is being revisited as a treatment option due to its broad-spectrum antimicrobial activity and low propensity for bacterial resistance. We assessed four well-characterised New Zealand honeys, quantified for their key antibacterial components, methylglyoxal, hydrogen peroxide and sugar, for their capacity to prevent and eradicate biofilms produced by the common wound pathogen Pseudomonas aeruginosa. We demonstrate that: (1) honey used at substantially lower concentrations compared to those found in honey-based wound dressings inhibited P. aeruginosa biofilm formation and significantly reduced established biofilms; (2) the anti-biofilm effect of honey was largely driven by its sugar component; (3) cells recovered from biofilms treated with sub-inhibitory honey concentrations had slightly increased tolerance to honey; and (4) honey used at clinically obtainable concentrations completely eradicated established P. aeruginosa biofilms. These results, together with their broad antimicrobial spectrum, demonstrate that manuka honey-based wound dressings are a promising treatment for infected chronic wounds, including those with P. aeruginosa biofilms.

Anti-biofilm effects and characterisation of the hydrogen peroxide activity of a range of Western Australian honeys compared to Manuka and multifloral honeys

The antibacterial activity of honeys derived from the endemic flora of the southwest corner of Western Australia, including the trees Jarrah (Eucalyptus marginata) and Marri (Corymbia calophylla), remains largely unexplored. Investigation of these honeys showed minimum inhibitory concentrations (MICs) of 6.7-28.0% (w/v) against Gram positive and negative bacteria. Honey solutions showed enhanced antibacterial activity after hydrogen peroxide was allowed to accumulate prior to testing, with a mean MIC after accumulation of 14.3% compared to 17.4% before accumulation. Antibacterial activity was reduced after treatment with catalase enzyme, with a mean MIC of 29.4% with catalase compared to 15.2% without catalase. Tests investigating the role of the Gram negative outer membrane in honey susceptibility revealed increases in activity after destabilisation of the outer membrane. Honeys reduced both the formation of biofilm and the production of bacterial pigments, which are both regulated by quorum sensing. However, these reductions were closely correlated with global growth inhibition. Honey applied to existing biofilms resulted in decreased metabolic activity and minor decreases in viability. These results enhance our understanding of the mechanisms of antibacterial action of Jarrah and Marri honeys, and provide further support for the use of honey in the treatment of infected wounds.

Honey: An Effective Regenerative Medicine Product in Wound Management

:

Honey has successfully been used in the treatment of a broad spectrum of injuries including burns and non-healing wounds. It acts as an antibacterial and anti-biofilm agent with anti/pro-inflammatory properties. However, besides these traditional properties, recent evidence suggests that honey is also an immunomodulator in wound healing and contains several bee and plant-derived components that may speed up wound healing and tissue regeneration process. Identifying their exact mechanism of action allows better understanding of honey healing properties and promotes its wider translation into clinical practice.

:

This review will discuss the physiological basis for the use of honey in wound management, its current clinical uses, as well as the potential role of honey bioactive compounds in dermal regenerative medicine and tissue re-modeling.

A cost-effective colourimetric assay for quantifying hydrogen peroxide in honey

Honey is a natural product with many beneficial properties including antimicrobial action. Production of hydrogen peroxide (H₂O₂) in diluted honey is central to this action. Here, we describe an optimized method for measuring levels of H₂O₂ in honey. This method is based on established methods, with the level of dilution, the time between dilution and reading the assay, and aeration of the samples during the assay identified as critical points for ensuring reliability and reproducibility. The method is cost-effective and easy to perform using common laboratory equipment. Using this method, we quantified the hydrogen peroxide content of five different, unprocessed polyfloral honeys collected in NC, USA. Our results show that H₂O₂ production by these honeys varies greatly, with some samples producing negligible levels of H₂O₂. We assessed the effect of colour on the assay by measuring the recovery of spiked H₂O₂ from light and dark honey and from serially diluted dark corn syrup, and found the amount of H₂O₂ that could be detected was lower in dark corn syrup and darker honey samples.

A Critical Review and Perspective of Honey in Tissue Engineering and Clinical Wound Healing

Significance: Historically, honey has been regarded as a potent agent in bacterial inhibition and wound healing. An increased prevalence of antibiotic resistant pathogens spurred an initial resurgence in honey's clinical popularity, with it quickly finding a place in wound care and regenerative medicine. However, this renewed usage demanded a need for improved delivery and overall research of its bioactive properties. This review provides an overview of the antibacterial properties and clinical use of honey. Recent Advances: The past and present clinical use of honey is noted, focusing specifically on burns and ulcers, as these are the most common applications of the natural agent. While honey is often used without modification clinically, there are also commercially available products ranging from dressings to gels, which are discussed. Critical Issues: Despite these products growing in popularity, the need for improved delivery and a structure to support wound healing could improve the treatment method. Future Directions: Tissue engineering scaffolds can provide an alternative method of honey delivery with research focusing primarily on electrospun scaffolds, hydrogels, and cryogels. Current studies on these scaffolds are discussed with respect to their advantages and potential for future clinical work. Overall, this review provides a comprehensive overview of the properties of honey, its current use in wound healing, and the potential for future incorporation into tissue-engineered scaffolds to provide an innovative wound healing agent.

In vitro evaluation of methicillin-resistant and methicillin-sensitive Staphylococcus aureus susceptibility to Saudi honeys

Background

Honey has been increasingly recognized as a potential therapeutic agent for treatment of wound infections. There is an urgent need for assessment and evaluation of the antibacterial properties against wound pathogens of honeys that have not yet been tested.

Methods

Ten Saudi honeys collected from different geographical locations were screened initially for their antibacterial potential against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) by the agar well diffusion method. Manuka honey (UMF-12) was used for comparison. Of the tested honeys, the honey that exhibited the greatest antibacterial activity in the agar well diffusion assay was further evaluated for its minimum inhibitory concentration (MIC) against ten MRSA clinical isolates and three American Type Culture Collection (ATCC) reference strains by the microbroth dilution method.

Results

Locally produced honeys exhibited variable antibacterial activity against the tested isolates in the agar well diffusion assay. They were unable to exhibit antibacterial activity against MSSA and MRSA at 25% dilutions (w/v) in catalase solution. However, Sumra and Talha honeys showed a zone of inhibition at 50% dilutions (w/v) in catalase solution. This finding means that both honeys possess weak non-peroxide-based antibacterial activity. Moreover, Sumra honey showed a larger inhibition zone at 50 and 25% dilutions (w/v) in distilled water than Manuka honey against both MSSA and MRSA. This result demonstrates that Sumra honey has more hydrogen peroxide-related antibacterial activity or total antibacterial activity than Manuka honey. In addition, MIC results obtained through a microbroth dilution assay showed that Sumra honey inhibited the growth of all MRSA clinical isolates (n = 10) and reference strains [MRSA (ATCC 43300) and MSSA (ATCC 29213)] at lower concentrations (12.0% v/v) than those required for Manuka honey-mediated inhibition (14.0% v/v). This result means that Sumra honey has more peroxide or synergistic antibacterial activity than Manuka honey. An equivalent MIC (15.0% v/v) was observed for E. coli (ATCC 25922) between Manuka honey and Sumra honey.

Conclusions

Sumra honey may be used as an alternative therapeutic agent for infected wounds and burns, where additional hydrogen peroxide-related antibacterial activity is needed. In the future, the physiochemical characteristics of Sumra honey may be evaluated and standardized.

Prolotherapy: Potential for the Treatment of Chronic Wounds?

Significance: Chronic skin ulcers, including venous, diabetic, and pressure ulcers, constitute a major health care burden, affecting 2-6 million people in the United States alone, with projected increases in incidence owing to the aging population and rising epidemic of diabetes. The ulcers are often accompanied by pain. Standard of care fails to heal ∼50% of diabetic foot ulcers and 25% of venous leg ulcers. Even advanced therapies do not heal >60%. Thus there is an unmet need for novel therapies that promote healing and also address the concomitant pain issue. Recent Advances: Prolotherapy involves injection of small amounts of an irritant material to the site of degenerated or painful joints, ligaments, and tendons. Multiple irritants are reported to be efficacious, but the focus here is on dextrose prolotherapy. In vitro and in vivo studies support translation to clinical use. Concentrations as low as 5% dextrose have resulted in production of growth factors that have critical roles in repair. Numerous clinical trials report pro-reparative effects of dextrose prolotherapy in joint diseases, tendon, and ligament damage, and for painful musculoskeletal issues. However, most of the studies have limitations that result in low-quality evidence. Critical Issues: The preclinical data support a role for dextrose prolotherapy in promoting tissue repair that is required for healing chronic wounds and ameliorating the associated pain. Critical issues include provision of evidence of efficacy in human chronic wounds. Another potential obstacle is limitation of reimbursement by third-party payers for a therapy with as yet limited evidence. Future Directions: Preclinical studies in models of chronic wounds would support clinical translation. As dextrose prolotherapy has some mechanistic similarities to already approved honey therapies, it may have a shortened pathway for clinical translation. The gold standard for widespread adoption would be a well-designed clinical trial.

Antimicrobial Activity of Agastache Honey and Characterization of Its Bioactive Compounds in Comparison With Important Commercial Honeys

There is an urgent need for new effective antimicrobial agents since acquired resistance of bacteria to currently available agents is increasing. The antimicrobial activity of Mono-floral Agastache honey produced from Australian grown Agastache rugosa was compared with the activity of commercially available honeys derived from Leptospermum species and with Jarrah honey for activity against clinical and non-clinical strains of Staphylococcus aureus (methicillin-susceptible and methicillin-resistant strains), Pseudomonas aeruginosa, and Escherichia coli. The minimum inhibitory concentration (MIC) for Agastache honey was in the range of 6-25% (w/v) for all species examined. The MICs for Leptospermum honeys were generally similar to those of Agastache honey, but MICs were higher for Super manuka and Jarrah honeys and lower for Tea tree honey. Staphylococci were more susceptible to all honeys than Pseudomonas aeruginosa and Escherichia coli. Pretreatment of honey with catalase increased the bacterial growth at MIC of Tea tree honey (35%), Super Manuka (15%), Jarrah honeys (12%), and Agastache honey (10%), indicating variable contributions of hydrogen peroxide to antimicrobial activity. Manuka and Jelly bush honeys retained their antimicrobial activity in the presence of catalase, indicating the presence of other antimicrobial compounds in the honey. An LC-MS/MS method was developed and used to identify possible antimicrobial phenolic compounds in Agastache honey and flowers, and five commercial honeys. The chemical markers characteristic of Agastache honey and honeys of Leptospermum origin were phenyllactic acid and methyl syringate. Overall, the bioactive compounds with antimicrobial and antioxidant activity in Agastache honey suggested a possible use for topical application and in wound care.

Antibacterial activity of Manuka honey and its components: An overview

The importance of honey for medicinal purposes is well documented in some of the world's oldest literature. Honey is well known and studied for its antimicrobial properties. The medicinal properties in honey originate from the floral source used by bees. Manuka honey is a dark monofloral honey rich in phenolic content, and currently it is gaining much attention for its antimicrobial activity. Researchers have found that honey is effective against a wide range of pathogens. The antibacterial potency of Manuka honey was found to be related to the Unique Manuka Factor (UMF) rating, which is correlated with the methylglyoxal and total phenols content. It is reported that different types of Manuka honey have differing effects and Gram-negative bacteria are more resistant than Gram-positive bacteria. Bacterial resistance to honey as antimicrobial agent has yet to be identified, possibly due to the presence of a complex mixture of methylglyoxal and other components. Honey is also reported to alter a bacterium's shape and size through septal ring alteration, which affects cell morphology and growth. Research has shown that Manuka honey of different UMF values has medicinal properties of interest and it can be beneficial when used as a combination treatment with other antimicrobial agents.

The Antibacterial Effect In Vitro of Honey Derived from Various Danish Flora

The mechanism behind the biologic actions of honey as a wound remedy has been intensively studied; however, there is no published data regarding any antibacterial effect of honey derived from Danish flora. We surveyed 11 honeys of various Danish floral sources for their antibacterial activity and compared them to a culinary processed commercial honey (Jakobsens) and a raw and a medical grade Manuka (Leptospermum scoparium) honey using the agar-well diffusion method. We tested the effect on three gram-positive bacteria (two strains of Staphylococcus aureus and one strain of Staphylococcus epidermidis) and two gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli). All samples, except the commercial honey, exhibited antibacterial activity, and samples derived from Water Mint (Mentha aquatica), Organic 2 (mixed organic flora), and Linden (Tilia cordata) honey had consistent effects on all bacteria tested and showed greater effect than medical grade and raw Manuka (L. scoparium) honey. The content of methylglyoxal was low in the Danish honey (< 2 μg/mL) and significantly (p<0.05) higher in both the raw and the medical grade Manuka (L. scoparium) honey, where the concentrations were, respectively, 6.29 μg/mL and 54.33 μg/mL. The antibacterial effect of Danish honeys was mostly due to hydrogen peroxide. We conclude that honeys derived from Danish flora possess antibacterial effect, probably by a hurdle effect of viscosity, osmolality, acidity, bioactive peptides, and most importantly the content of hydrogen peroxide. These findings indicate that honeys of various Danish floral sources may have clinical potential, although further studies are necessary to elucidate this in order to determine whether the results of our in vitro experiments also apply to a clinical setting.

Honey, Wound Repair and Regenerative Medicine

Honey possesses anti-bacterial, anti-inflammatory and other properties that are useful for wound healing and tissue regeneration. Furthermore, honey has been used for millennia in folk medicine. The misuse of antibiotics has again boosted the use of honey in regenerative medicine. The multifaceted properties of honey could possibly be exploited for scaffold applications in tissue healing.