Manuka honey as a non-antibiotic alternative against Staphylococcus spp. and their small colony variant (SCVs) phenotypes

The antibiotic resistance (ABR) crisis is an urgent global health priority. Staphylococci are among the problematic bacteria contributing to this emergency owing to their recalcitrance to many clinically important antibiotics. Staphylococcal pathogenesis is further complicated by the presence of small colony variants (SCVs), a bacterial subpopulation displaying atypical characteristics including retarded growth, prolific biofilm formation, heightened antibiotic tolerance, and enhanced intracellular persistence. These capabilities severely impede current chemotherapeutics, resulting in chronic infections, poor patient outcomes, and significant economic burden. Tackling ABR requires alternative measures beyond the conventional options that have dominated treatment regimens over the past 8 decades. Non-antibiotic therapies are gaining interest in this arena, including the use of honey, which despite having ancient therapeutic roots has now been reimagined as an alternative treatment beyond just traditional topical use, to include the treatment of an array of difficult-to-treat staphylococcal infections. This literature review focused on Manuka honey (MH) and its efficacy as an anti-staphylococcal treatment. We summarized the studies that have used this product and the technologies employed to study the antibacterial mechanisms that render MH a suitable agent for the management of problematic staphylococcal infections, including those involving staphylococcal SCVs. We also discussed the status of staphylococcal resistance development to MH and other factors that may impact its efficacy as an alternative therapy to help combat ABR.

Studies on bioactivities of Manuka and regional varieties of honey for their potential use as natural antibiotic agents for infection control related to wound healing and in pharmaceutical formulations

Presently, most of the reported infections are of a bacterial origin; however, this leads to a limit within the literature and research around infections caused by fungal pathogens, which are now developing resistance to antibiotic medicines. Of the natural antimicrobial agents, honey has been observed with demonstrable and highly exploitable antimicrobial and infection control related to wound healing properties; therefore, it has been incorporated into many standard pharmaceutical formulations. Generally, these products utilize a pure sample of honey as a bioactive ingredient in a product which has been purposely designed for the convenience of application. This article aims to review information available from published reports on various bioactivities of a variety of medical-grade honey products, including manuka and other conventional non-manuka types sourced from different floral types and geographical regions. Additionally, this review highlights the antibiotic activities of various types of honey products tested against pathogenic strains of bacteria, yeast and fungi, and their applications in the formulation of healthcare products.

Cadaver preservative properties of a solution composed of honey, ethyl alcohol, liquid paraffin, distilled water and citric acid: Experiments on rabbit cadavers

The objective of this study is to assess the efficacy of a solution including honey, ethyl alcohol, liquid paraffin, distilled water and citric acid (HEFS) as a preservative for rabbit cadavers, serving as a potential substitute for formaldehyde. The cadavers underwent preservation using three distinct solutions: 10% formalin, 35% alcohol and HEFS. The cadavers were subjected to a total of four sampling events, occurring at 4-month intervals, in order to collect specimens for microanatomical, histological, microbiological, mycological, colourimetric, texture and odour analysis. In terms of hardness, suitability for dissection and joint mobility metrics, the cadavers fixed with HEFS had superior qualities to those fixed with formalin. The fixation quality of HEFS for histological analyses was deemed acceptable, except kidney and intestinal tissues. In texture analysis, differences only in the elasticity parameter (p < 0.05) in the same sampling period. A total of 10 (13.9) bacteria isolates were identified among which, Metasolibacillus meyeri 3 (30%) was predominantly followed by Staphylococcus aureus 2 (20%), Bacillus siamensis, Bacillus subtilis, Pseudarthrobacter oxydans, Bacillus licheniformis, Bacillus subtilis subsp. subtilis with a proportion of 1 (10%), respectively, by both microbiological and molecular analysis. However, no anaerobic bacteria and fungi were isolated. A considerable percentage of the students had the perception that HEFS was appropriate for utilization in laboratory settings due to its absence of unpleasant odours and detrimental impact on ocular and respiratory functions. In conclusion, we consider that HEFS may serve as a viable substitute for formalin solution in the preservation of rabbit cadavers.

The Antimicrobial and Antibiofilm Abilities of Fish Oil Derived Polyunsaturated Fatty Acids and Manuka Honey

Both honey and fish oil have been historically used in medicine and identified as having antimicrobial properties. Although analyses of the substances have identified different components within them, it is not fully understood how these components interact and contribute to the observed effect. With the increase in multi-drug resistant strains of bacteria found in infections, new treatment options are needed. This study aimed to assess the antimicrobial abilities of fish oil components, including docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and derived resolvins (RvE1, RvD2, and RvD3), as well as two varieties of manuka honey, against a panel of medically relevant microorganisms and antimicrobial resistant organisms, such as Methicillin Resistant Staphylococcus aureus (MRSA) and carbapenem-resistant Escherichia coli. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were identified; further minimum biofilm eradication concentrations (MBEC) were investigated for responsive organisms, including S. aureus, E. coli, Staphylococcus epidermidis, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Concurrent with the existing literature, manuka honey was found to be a broad-spectrum antimicrobial with varied potency according to methylglyoxal content. DHA and EPA were both effective against Gram-positive and negative bacteria, but some drug-resistant strains or pathogens were not protected by a capsule. Only E. coli was inhibited by the resolvins.

Anti-bacterial, anti-biofilm and anti-quorum sensing activities of honey: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Man has used honey to treat diseases since ancient times, perhaps even before the history of medicine itself. Several civilizations have utilized natural honey as a functional and therapeutic food to ward off infections. Recently, researchers worldwide have been focusing on the antibacterial effects of natural honey against antibiotic-resistant bacteria.

AIM OF THE STUDY

This review aims to summarize research on the use of honey properties and constituents with their anti-bacterial, anti-biofilm, and anti-quorum sensing mechanisms of action. Further, honey's bacterial products, including probiotic organisms and antibacterial agents which are produced to curb the growth of other competitor microorganisms is addressed.

MATERIALS AND METHODS

In this review, we have provided a comprehensive overview of the antibacterial, anti-biofilm, and anti-quorum sensing activities of honey and their mechanisms of action. Furthermore, the review addressed the effects of antibacterial agents of honey from bacterial origin. Relevant information on the antibacterial activity of honey was obtained from scientific online databases such as Web of Science, Google Scholar, ScienceDirect, and PubMed.

RESULTS

Honey's antibacterial, anti-biofilm, and anti-quorum sensing activities are mostly attributed to four key components: hydrogen peroxide, methylglyoxal, bee defensin-1, and phenolic compounds. The performance of bacteria can be altered by honey components, which impact their cell cycle and cell morphology. To the best of our knowledge, this is the first review that specifically summarizes every phenolic compound identified in honey along with their potential antibacterial mechanisms of action. Furthermore, certain strains of beneficial lactic acid bacteria such as Bifidobacterium, Fructobacillus, and Lactobacillaceae, as well as Bacillus species can survive and even grow in honey, making it a potential delivery system for these agents.

CONCLUSION

Honey could be regarded as one of the best complementary and alternative medicines. The data presented in this review will enhance our knowledge of some of honey's therapeutic properties as well as its antibacterial activities.

Combinatorial efficacy of Manuka honey and antibiotics in the in vitro control of staphylococci and their small colony variants

Introduction

Staphylococci are among the list of problematic bacteria contributing to the global antibiotic resistance (ABR) crisis. Their ability to adopt the small colony variant (SCV) phenotype, induced by prolonged antibiotic chemotherapy, complicates staphylococcal infection control options. Novel and alternative approaches are needed to tackle staphylococcal infections and curb ABR. Manuka honey (MH), a non-antibiotic alternative is recognized for its unique antibacterial activity based on its methylglyoxal (MGO) component.

Methods

In this study, MH (MGO 830+) was tested in combination with gentamicin (GEN), rifampicin (RIF), or vancomycin (VA) against staphylococcal wildtype (WT) and SCVs. To our knowledge, there are no current studies in the literature documenting the effects of MH on staphylococcal SCVs. While Staphylococcus aureus is well-studied for its international ABR burden, limited data exists demonstrating the effects of MH on S. epidermidis and S. lugdunensis whose pathogenic relevance and contribution to ABR is also rising.

Results & discussion

The three staphylococci were most susceptible to RIF (0.06-0.24 μg/ml), then GEN (0.12-0.49 μg/ml), and lastly VA (0.49-0.96 μg/ml). The MICs of MH were 7%, 7-8%, and 6-7% (w/v), respectively. Fractional inhibitory concentration (FIC) evaluations showed that the combined MH + antibiotic effect was either additive (FICI 1-2), or partially synergistic (FICI >0.5-1). While all three antibiotics induced SCVs in vitro, stable SCVs were observed in GEN treatments only. The addition of MH to these GEN-SCV-induction analyses resulted in complete suppression of SCVs (p<0.001) in all three staphylococci, suggesting that MH's antibacterial properties interfered with GEN's SCV induction mechanisms. Moreover, the addition of MH to growth cultures of recovered stable SCVs resulted in the inhibition of SCV growth by at least 99%, indicating MH's ability to prevent subsequent SCV growth. These in vitro analyses demonstrated MH's broad-spectrum capabilities not only in improving WT staphylococci susceptibility to the three antibiotics, but also mitigated the development and subsequent growth of their SCV phenotypes. MH in combination with antibiotics has the potential to not only resensitize staphylococci to antibiotics and consequently require less antibiotic usage, but in instances where prolonged chemotherapy is employed, the development and growth of SCVs would be hampered, providing a better clinical outcome, all of which mitigate ABR.

Evaluation of the polyphenolic profile of native Ecuadorian stingless bee honeys (Tribe: Meliponini) and their antibiofilm activity on susceptible and multidrug-resistant pathogens: An exploratory analysis

Biofilms are associated with infections that are resistant to conventional therapies, contributing to the antimicrobial resistance crisis. The need for alternative approaches against biofilms is well-known. Although natural products like stingless bee honeys (tribe: Meliponini) constitute an alternative treatment, much is still unknown. Our main goal was to evaluate the antibiofilm activity of stingless bee honey samples against multidrug-resistant (MDR) pathogens through biomass assays, fluorescence (cell count and viability), and scanning electron (structural composition) microscopy. We analyzed thirty-five honey samples at 15% (v/v) produced by ten different stingless bee species (Cephalotrigona sp., Melipona sp., M. cramptoni, M. fuscopilosa, M. grandis, M. indecisa, M. mimetica, M. nigrifacies, Scaptotrigona problanca, and Tetragonisca angustula) from five provinces of Ecuador (Tungurahua, Pastaza, El Oro, Los Ríos, and Loja) against 24-h biofilms of Staphylococcus aureus, Klebsiella pneumoniae, Candida albicans, and Candida tropicalis. The present honey set belonged to our previous study, where the samples were collected in 2018-2019 and their physicochemical parameters, chemical composition, mineral elements, and minimal inhibitory concentration (MIC) were screened. However, the polyphenolic profile and their antibiofilm activity on susceptible and multidrug-resistant pathogens were still unknown. According to polyphenolic profile of the honey samples, significant differences were observed according to their geographical origin in terms of the qualitative profiles. The five best honey samples (OR24.1, LR34, LO40, LO48, and LO53) belonging to S. problanca, Melipona sp., and M. indecisa were selected for further analysis due to their high biomass reduction values, identification of the stingless bee specimens, and previously reported physicochemical parameters. This subset of honey samples showed a range of 63-80% biofilm inhibition through biomass assays. Fluorescence microscopy (FM) analysis evidenced statistical log reduction in the cell count of honey-treated samples in all pathogens (P <0.05), except for S. aureus ATCC 25923. Concerning cell viability, C. tropicalis, K. pneumoniae ATCC 33495, and K. pneumoniae KPC significantly decreased (P <0.01) by 21.67, 25.69, and 45.62%, respectively. Finally, scanning electron microscopy (SEM) analysis demonstrated structural biofilm disruption through cell morphological parameters (such as area, size, and form). In relation to their polyphenolic profile, medioresinol was only found in the honey of Loja, while scopoletin, kaempferol, and quercetin were only identified in honey of Los Rios, and dihydrocaffeic and dihydroxyphenylacetic acids were only detected in honey of El Oro. All the five honey samples showed dihydrocoumaroylhexose, luteolin, and kaempferol rutinoside. To the authors' best knowledge, this is the first study to analyze stingless bees honey-treated biofilms of susceptible and/or MDR strains of S. aureus, K. pneumoniae, and Candida species.

Evidence for Natural Products as Alternative Wound-Healing Therapies

Chronic, non-healing wounds represent a significant area of unmet medical need and are a growing problem for healthcare systems around the world. They affect the quality of life for patients and are an economic burden, being difficult and time consuming to treat. They are an escalating problem across the developed world due to the increasing incidence of diabetes and the higher prevalence of ageing populations. Effective treatment options are currently lacking, and in some cases chronic wounds can persist for years. Some traditional medicines are believed to contain bioactive small molecules that induce the healing of chronic wounds by reducing excessive inflammation, thereby allowing re-epithelisation to occur. Furthermore, many small molecules found in plants are known to have antibacterial properties and, although they lack the therapeutic selectivity of antibiotics, they are certainly capable of acting as topical antiseptics when applied to infected wounds. As these molecules act through mechanisms of action distinct from those of clinically used antibiotics, they are often active against antibiotic resistant bacteria. Although there are numerous studies highlighting the effects of naturally occurring small molecules in wound-healing assays in vitro, only evidence from well conducted clinical trials can allow these molecules or the remedies that contain them to progress to the clinic. With this in mind, we review wound-healing natural remedies that have entered clinical trials over a twenty-year period to the present. We examine the bioactive small molecules likely to be in involved and, where possible, their mechanisms of action.

Synergic Effect of Honey with Other Natural Agents in Developing Efficient Wound Dressings

Honey has been used for therapeutic and nutritional purposes since ancient times. It was considered one of the essential medical assets in wound healing. According to research, honeybees have significant antibacterial, antioxidant, anti-inflammatory, antitumor, and wound-healing properties. Lately, scientific researchers have focused on apitherapy, using bee products to protect and strengthen the immune system. Since honey is the most important natural product rich in minerals, proteins, and vitamins, it has been intensively used in such therapies. Honey has gained significant consideration because of the beneficial role of its antioxidant compounds, such as enzymes, proteins, amino and organic acids, polyphenols, and carotenoids, but mainly due to flavonoids and phenolic acids. It has been proven that phenolic compounds are responsible for honey's biological activity and that its physicochemical properties, antioxidants, and antimicrobial potential are significant for human health. The review also presents some mechanisms of action and the medical applications of honey, such as wound healing dressings, skin grafts, honey-based nanofibers, and cochlear implants, as the most promising wound healing tools. This extensive review has been written to highlight honey's applications in medicine; its composition with the most important bioactive compounds also illustrates its synergistic effect with other natural products having remarkable therapeutic properties in wound healing.

Antimicrobial Evaluation of Various Honey Types against Carbapenemase-Producing Gram-Negative Clinical Isolates

The development of antibiotic resistance is a major public health issue, as infections are increasingly unresponsive to antibiotics. Emerging antimicrobial resistance has raised researchers’ interest in the development of alternative strategies using natural compounds with antibacterial activity, like honey, which has emerged as an agent to treat several infections and wound injuries. Nevertheless, the antibacterial effect of honey was mostly evaluated against Gram-positive bacteria. Hence, the objective of our study was to evaluate the antibacterial activity, as well as the physicochemical parameters, of genuine Greek honeys against multidrug-resistant Gram-negative pathogenic bacteria. In this vein, we aimed to study the in vitro antibacterial potential of rare Greek honeys against Verona integron-encoded metallo-β-lactamase (VIM)- or Klebsiella pneumoniae carbapenemase-producing multidrug-resistant Gram-negative pathogens. Physicochemical parameters such as pH, hydrogen peroxide, free acidity, lactonic acid, total phenols total flavonoids, free radical scavenging activities, tyrosinase enzyme inhibitory activity and kojic acid were examined. Moreover, the antimicrobial activity of 10 different honey types was evaluated in five consecutive dilutions (75%, 50%, 25%, 12.5% and 6.25%) against the clinical isolates by the well diffusion method, as well as by the determination of the minimum inhibition concentration after the addition of catalase and protease. Almost all the physicochemical parameters varied significantly among the different honeys. Fir and manuka honey showed the highest values in pH and H₂O₂, while the free acidity and lactonic acid levels were higher in chestnut honey. Total phenols, total flavonoids and free radical scavenging activities were found higher in cotton, arbutus and manuka honey, and finally, manuka and oregano honeys showed higher tyrosinase inhibition activity and kojic acid levels. The antimicrobial susceptibility depended on the type of honey, on its dilution, on the treatment methodology and on the microorganism. Arbutus honey was the most potent against VIM-producing Enterobacter cloacae subsp. dissolvens in 75% concentration, while fir honey was more lethal for the same microorganism in the 25% concentration. Many honeys outperformed manuka honey in their antibacterial potency. It is of interest that, for any given concentration in the well diffusion method and for any given type of honey, significant differences were not detected among the four multidrug-resistant pathogens, which explains that the damaging effect to the bacterial cells was the same regardless of the bacterial species or strain. Although the antimicrobial potency of different honey varieties dependents on their geographical origin and on their compositional differences, the exact underlying mechanism remains yet unclear.

Treatment of Pasteurella multocida infection with dressings containing honey and antibacterials: a case report

Infections secondary to Pasteurella multocida frequently occur in patients who have been exposed to domestic pets. Human infections caused by Pasteurella multocida vary in severity, and clinical features include localised cellulitis, osteomyelitis, systemic bacteraemia, meningitis and pneumonia. No vaccine has been developed against Pasteurella multocida; it is treated with antibacterial agents and, in most cases, surgical intervention. This article discusses the authors' experience in treating a woman with severe cellulitis and osteomyelitis on her hand caused by Pasteurella multocida. She refused surgical intervention and was successfully treated with honey-containing dressings and antibiotics after failure to heal following conservative treatment using conventional wound dressings combined with antibiotics.

Honey as an Ecological Reservoir of Antibacterial Compounds Produced by Antagonistic Microbial Interactions in Plant Nectars, Honey and Honey Bee

The fundamental feature of "active honeys" is the presence and concentration of antibacterial compounds. Currently identified compounds and factors have been described in several review papers without broader interpretation or links to the processes for their formation. In this review, we indicate that the dynamic, antagonistic/competitive microbe-microbe and microbe-host interactions are the main source of antibacterial compounds in honey. The microbial colonization of nectar, bees and honey is at the center of these interactions that in consequence produce a range of defence molecules in each of these niches. The products of the microbial interference and exploitive competitions include antimicrobial peptides, antibiotics, surfactants, inhibitors of biofilm formation and quorum sensing. Their accumulation in honey by horizontal transfer might explain honey broad-spectrum, pleiotropic, antibacterial activity. We conclude that honey is an ecological reservoir of antibacterial compounds produced by antagonistic microbial interactions in plant nectars, honey and honey bee. Thus, refocusing research on secondary metabolites resulting from these microbial interactions might lead to discovery of new antibacterial compounds in honey that are target-specific, i.e., acting on specific cellular components or inhibiting the essential cellular function.

Antibacterial activity of honeys from Amazonian stingless bees of Melipona spp. and its effects on bacterial cell morphology

BACKGROUND

Stingless bee honey has great therapeutic potential, especially as an antimicrobial agent. In the present study, we evaluated the in vitro antibacterial potential of honey from Melipona spp. with occurrence in Rio Branco-AC and Xapuri-AC from the Amazonian region. Samples were collected from the species Melipona eburnea, Melipona grandis, Melipona flavolineata and Melipona seminigra. The antibacterial activity of the honey samples was tested against standard Gram-positive and Gram-negative bacteria and two strains isolated from bovine mastitis.

RESULTS

In the agar diffusion assay, we observed antibacterial activity for the four honeys against the tested strains. The honey from M. flavolineata showed a minimmum inhibitory concentration (MIC) lower than 3.12% (v/v). The minimum bactericidal concentration values were larger than the MIC for most of the microorganisms tested. Scanning electron microscopy (SEM) showed the damaging effect of the honey of M. flavolineata on Staphylococcus aureus cells, as well as its inhibitory effect on cell division.

CONCLUSION

The results of the present study demonstrate that the honey from stingless bees possesses in vitro antimicrobial activity against pathogenic bacteria. The effects observed by SEM show that honey from the Amazonian stingless bee M. flavolineata has promising therapeutic potential as a future antimicrobial agent. © 2020 Society of Chemical Industry.

The stingless bee honey protects against hydrogen peroxide-induced oxidative damage and lipopolysaccharide-induced inflammation in vitro

Oxidative stress, DNA damage, and unresolved inflammation are the predisposing factors of many chronic and degenerative diseases, including cancer. Stingless bee honey (SBH) is recognized to have high medicinal value by traditional medicine practitioners and has been used to treat various illnesses traditionally. This study aimed to determine the antioxidant, anti-inflammatory, and genoprotective effects of SBH by using in vitro cell culture models. The sugar content, total phenolic content, radical scavenging activity, and ferric reducing antioxidant power (FRAP) of SBH were determined in this study. Then, the protective effect of SBH against hydrogen peroxide (H₂O₂)-induced cell death and DNA damage was studied by using WIL2-NS human lymphoblastoid cell line, while the lipopolysaccharide (LPS)-induced RAW 264.7 murine macrophages cell line was used to study the anti-inflammatory effects of SBH. Results from this present study showed that the major sugar contents of SBH were fructose (19.39 + 0.01%) and glucose (14.03 ± 0.03%). Besides, the total phenolic content, the radical scavenging activity, and the FRAP value of SBH were 15.38 ± 0.02 mg GAE/100 g of honey, 34.04 ± 0.21%, and 206.77 + 1.76 μM AAE/100 g honey respectively. Pretreatment with SBH protected WIL2-NS cells from H₂O₂-induced cell death and DNA damage (p < 0.001). Moreover, SBH was also able to attenuate the production of nitric oxide by inhibiting the expression of inducible nitric oxide synthase in LPS-induced RAW 264.7 cells (p < 0.001). In conclusion, SBH is rich in total phenolic content and possesses strong antioxidant, anti-inflammatory, and genoprotective properties. Our current findings suggest that SBH might be useful in the prevention and treatment of many diseases caused by oxidative stress and inflammation assuming the observed effects are also achievable in vivo.

Randomised assessormasked trial evaluating topical manuka honey (Optimel) in treatment of meibomian gland dysfunction

PURPOSE

To evaluate the effects of manuka honey eye-drops in the treatment of meibomian gland dysfunction.

METHODS

This is an assessor-masked (single-blind), randomised controlled trial comparing conventional treatment group with interventional group using Optimel 16% manuka honey topical eye-drops. 59 patients were recruited to the study and randomised into two groups: one given regular lubricants and the other given Optimel 16% manuka honey eye-drops. The Standard Patient Evaluation of Eye Dryness (SPEED) score was measured at baseline and on follow-up. 4 patients were lost to follow-up. Multiple ocular surface parameters were graded from slit lamp examination by a masked assessor. Results were compared from baseline to follow-up date 3 weeks later.

RESULTS

Patients in the conventional treatment group demonstrated minimal difference in SPEED score at 3-week follow-up (mean difference 1.087, p=0.183), which was not statistically significant. However, measurements of tear film break-up time, corneal surface stain (Oxford), lid margin, conjunctival redness, as well as meibum quality and expressibility showed significant improvements at 3 weeks (p<0.01). Patients in the manuka honey eye-drops group showed significant difference after 3 weeks in SPEED score (mean difference 2.53, p=0.006), as well as in lid margin redness, conjunctival redness, corneal surface stain (Oxford), and meibum quality and expressibility (p=0.000).

CONCLUSIONS

Optimel 16% manuka honey eye-drops showed significant improvement in symptoms and objective signs in meibomian gland dysfunction and are an effective alternative treatment for meibomian gland dysfunction.

TRIAL REGISTRATION NUMBER

NCT04457648.

Antibacterial Activity of Honey against Methicillin-Resistant and Sensitive Staphylococcus Aureus Isolated from Patients with Diabetic Foot Ulcer

Introduction:

Staphylococcus aureus is the most important causative agent of wound infections, including diabetic foot ulcers. Honey is a very useful nutrient with antimicrobial properties and other biological properties such as antitumor, anti-inflammatory, antioxidant and antiviral properties. The aim was to examine the antibacterial activity of honey against methicillin-resistant and sensitive S. aureus (MRSA and MSSA) isolated from patients with diabetic foot ulcers.

Methods:

This cross-sectional study was performed from January 2019 to December 2019. Twenty S. aureus isolates were collected from patients with diabetic foot ulcers. Different concentrations (100%, 70%, 50%, 25% vol/vol) of honey were studied. Dilutions of honey solutions were examined to determine the minimum inhibitory concentration (MIC) against S. aureus. MICs were determined by spectrophotometric assay at 620 nm.

Results:

All strains showed sensitivity to honey with MIC equal to 25% (vol/vol). The MIC (%) values of honey for all studied S. aureus (MRSA and MSSA) isolates ranged between 18-100% (v/v).

Conclusion:

Honey with confirmed, antibacterial activity has the potential to be an efficient treatment complementary for diabetic foot ulcers infected or at risk of infection with S. aureus.

Honey: Another Alternative in the Fight against Antibiotic-Resistant Bacteria?

Antibacterial resistance has become a challenging situation worldwide. The increasing emergence of multidrug-resistant pathogens stresses the need for developing alternative or complementary antimicrobial strategies, which has led the scientific community to study substances, formulas or active ingredients used before the antibiotic era. Honey has been traditionally used not only as a food, but also with therapeutic purposes, especially for the topical treatment of chronic-infected wounds. The intrinsic characteristics and the complex composition of honey, in which different substances with antimicrobial properties are included, make it an antimicrobial agent with multiple and different target sites in the fight against bacteria. This, together with the difficulty to develop honey-resistance, indicates that it could become an effective alternative in the treatment of antibiotic-resistant bacteria, against which honey has already shown to be effective. Despite all of these assets, honey possesses some limitations, and has to fulfill a number of requirements in order to be used for medical purposes.

Use of a model to understand the synergies underlying the antibacterial mechanism of H2O2-producing honeys

Honey has been valued as a powerful antimicrobial since ancient times. However, the understanding of the underlying antibacterial mechanism is incomplete. The complexity and variability of honey composition represent a challenge to this scope. In this study, a simple model system was used to investigate the antibacterial effect of, and possible synergies between, the three main stressors present in honey: sugars, gluconic acid, and hydrogen peroxide (H₂O₂), which result from the enzymatic conversion of glucose on honey dilution. Our results demonstrated that the synergy of H₂O₂ and gluconic acid is essential for the antibacterial activity of honey. This synergy caused membrane depolarization, destruction of the cell wall, and eventually growth inhibition of E. coli K-12. The presence of H₂O₂ stimulated the generation of other long-lived ROS in a dose-dependent manner. Sugars caused osmosis-related morphological changes, however, decreased the toxicity of the H₂O₂/gluconic acid. The susceptibility of catalase and general stress response sigma factor mutants confirmed the synergy of the three stressors, which is enhanced at higher H₂O₂ concentrations. By monitoring cellular phenotypic changes caused by model honey, we explained how this can be bactericidal even though the antimicrobial compounds which it contains are at non-inhibitory concentrations.

Inhibition of Staphylococcus aureus LC554891 by Moringa oleifera Seed Extract either Singly or in Combination with Antibiotics

Bacterial outbreaks caused by Staphylococcus aureus (S. aureus) are interesting due to the existence of multidrug resistant (MDR) isolates. Therefore, there is a need to develop novel ways to control such MDR S. aureus. In this study, some natural agents such as honey bee (HB), extracts of either Moringa oleifera seeds (MSE), or leaves (MLE) and essential oils of garlic, clove, and moringa were studied for their inhibitory activity against this S. aureus pathogen. About 100 food samples including beef luncheon (n = 25), potato chips (n = 50), and corn flakes (n = 25) were investigated for possible pollution with the S. aureus bacteria. The isolated bacteria suspected to belong S. aureus that grew well onto Baird-Parker agar (Oxoid) and shiny halo zones and positive coagulase reaction were selected and identified by API-Kits; all of them that were approved belong to S. aureus (18 strains). The sensitivity of the obtained 18 S. aureus bacterial strains to 12 antibiotics were evaluated; all of them were resistant to ofloxacin; however, other antibiotics tested showed variable results. Interestingly, the S. aureus No. B3 isolated from beef luncheon was resistant to10 antibiotics out of 12 ones tested. Multiple antibiotic resistance index (MAR) of this S. aureus strain was about 83.3%. Therefore, its identification was confirmed by sequencing of a 16S rRNA gene which approved a successful biochemical identification carried out by API Kits and such strain was designated S. aureus LC 554891. The genome of such strain appeared to contain mecA gene encoding methicillin resistance; it was found to contain hla, hlb, tsst-1, and finbA that encode α-blood hemolysis, β-blood hemolysis, toxic shock syndrome gene, and fibrinogen-binding protein gene, respectively. In addition, the virulence factors viz. sea; seb; sec encoding enterotoxins were detected in the DNA extracted from S. aureus B3 strain. Aqueous extract of Moringa oleifera seeds (MSE) showed inhibitory activity against S. aureus LC 554891 better than that obtained by tetracycline, essential oils or HB. Minimum inhibitory concentration (MIC) of MSE was 20µg/mL. Instrumental analysis of MSE showed 14 bioactive chemical compounds. Combinations of both MSE and tetracycline showed distinctive inhibitory activity against S. aureus LC 554891 than that obtained by either tetracycline or MSE singly.

Antibacterial and Antivirulence Activity of Manuka Honey against Genetically Diverse Staphylococcus pseudintermedius Strains

Staphylococcus pseudintermedius is an important member of the skin microbial community in animals and can cause opportunistic infections in both pets and their owners. The high incidence of antimicrobial resistance in S. pseudintermedius highlights that this opportunistic zoonotic pathogen can cause infections which require prolonged and intensive treatment to resolve. Manuka honey has proven efficacy against many bacterial pathogens and is an accepted topical treatment for infections in both veterinary and clinical practice, and so it is a particularly appropriate antimicrobial for use with zoonotic pathogens such as S. pseudintermedius. Here, we demonstrate that not only is manuka honey highly potent against novel multidrug-resistant S. pseudintermedius isolates, it also acts synergistically with clinically relevant antibiotics. In addition, manuka honey modulates S. pseudintermedius virulence activity, even at subinhibitory concentrations. In a clinical setting, these attributes may assist in controlling infection, allowing a more rapid resolution and reducing antibiotic use.

Staphylococcus pseudintermedius causes opportunistic infections in dogs. It also has significant zoonotic potential, with the emergence of multidrug resistance leading to difficulty treating both animal and human infections. Manuka honey has previously been reported to inhibit many bacterial pathogens, including methicillin-resistant Staphylococcus aureus, and is successfully utilized in both clinical and veterinary practice. Here, we evaluated the ability of manuka honey to inhibit strains of S. pseudintermedius grown alone and in combination with antibiotics, as well as its capacity to modulate virulence within multiple S. pseudintermedius isolates. All 18 of the genetically diverse S. pseudintermedius strains sequenced and tested were inhibited by ≤12% (wt/vol) medical-grade manuka honey, although tolerance to five clinically relevant antibiotics was observed. The susceptibility of the isolates to four of these antibiotics was significantly increased (P ≤ 0.05) when combined with sublethal concentrations of honey, although sensitivity to oxacillin was decreased. Virulence factor (DNase, protease, and hemolysin) activity was also significantly reduced (P ≤ 0.05) in over half of isolates when cultured with sublethal concentrations of honey (13, 9, and 10 isolates, respectively). These findings highlight the potential for manuka honey to be utilized against S. pseudintermedius infections.

IMPORTANCEStaphylococcus pseudintermedius is an important member of the skin microbial community in animals and can cause opportunistic infections in both pets and their owners. The high incidence of antimicrobial resistance in S. pseudintermedius highlights that this opportunistic zoonotic pathogen can cause infections which require prolonged and intensive treatment to resolve. Manuka honey has proven efficacy against many bacterial pathogens and is an accepted topical treatment for infections in both veterinary and clinical practice, and so it is a particularly appropriate antimicrobial for use with zoonotic pathogens such as S. pseudintermedius. Here, we demonstrate that not only is manuka honey highly potent against novel multidrug-resistant S. pseudintermedius isolates, it also acts synergistically with clinically relevant antibiotics. In addition, manuka honey modulates S. pseudintermedius virulence activity, even at subinhibitory concentrations. In a clinical setting, these attributes may assist in controlling infection, allowing a more rapid resolution and reducing antibiotic use.

Effect of manuka honey on biofilm-associated genes expression during methicillin-resistant Staphylococcus aureus biofilm formation

Methicillin-resistant Staphylococcus aureus (MRSA) are among the most important biofilm-forming pathogens responsible for hard-to-treat infections. Looking for alternatives to antibiotics that prevent biofilm formation, we investigated the effects of manuka honey on the transcriptional profile of genes essential for staphylococcal biofilm formation using qRT-PCR. mRNA from two hospital MRSA strains (strong and weak biofilm producer) were isolated after 4, 8, 12 and 24 h from cells grown in biofilm. Manuka honey at 1/2 minimum biofilm inhibition concentration (MBIC) significantly reduced MRSA cell viability in biofilm. Manuka honey downregulated the genes encoding laminin- (eno), elastin- (ebps) and fibrinogen binding protein (fib), and icaA and icaD involved in biosynthesis of polysaccharide intercellular adhesin in both weakly and strongly adhering strain compared to the control (untreated biofilm). Expression levels of cna (collagen binding protein) and map/eap (extracellular adherence protein—Eap) were reduced in weakly adhering strain. The lowest expression of investigated genes was observed after 12 h of manuka honey treatment at 1/2 MBIC. This study showed that the previously unknown mechanism of manuka honey action involved inhibition of S. aureus adhesion due to reduction in expression of crucial genes associated with staphylococcal biofilm.

Manuka honey microneedles for enhanced wound healing and the prevention and/or treatment of Methicillin-resistant Staphylococcus aureus (MRSA) surgical site infection

Manuka honey (MH) is currently used as a wound treatment and suggested to be effective in Methicillin-resistant Staphylococcus aureus (MRSA) elimination. We sought to optimize the synthesis of MH microneedles (MHMs) while maintaining the MH therapeutic effects. MHMs were synthesized using multiple methods and evaluated with in vitro assays. MHMs demonstrated excellent bactericidal activity against MRSA at concentrations ≥ 10% of honey, with vacuum-prepared honey appearing to be the most bactericidal, killing bacterial concentrations as high as 8 × 10⁷ CFU/mL. The wound-healing assay demonstrated that, at concentrations of 0.1%, while the cooked honey had incomplete wound closure, the vacuum-treated honey trended towards faster wound closure. In this study, we demonstrate that the method of MHM synthesis is crucial to maintaining MH properties. We optimized the synthesis of MHMs and demonstrated their potential utility in the treatment of MRSA infections as well as in wound healing. This is the first report of using MH as a substrate for the formation of dissolvable microneedles. This data supports the need for further exploration of this new approach in a wound-healing model and opens the door for the future use of MH as a component of microneedle scaffolds.

Manuka honey modulates the release profile of a dHL-60 neutrophil model under anti-inflammatory stimulation

Manuka honey, a wound treatment used to eradicate bacteria, resolve inflammation, and promote wound healing, is a current focus in the tissue engineering community as a tissue template additive. However, Manuka honey's effect on neutrophils during the inflammation-resolving phase has yet to be examined. This study investigates the effect of 0.5% and 3% Manuka honey on the release of cytokines, chemokines, and matrix-degrading enzymes from a dHL-60 neutrophil model in the presence of anti-inflammatory stimuli (TGF-β, IL-4, IL-4 +IL-13). We hypothesized that Manuka honey would reduce the output of pro-inflammatory signals and increase the release of anti-inflammatory signals. The results of this study indicate that 0.5% honey significantly increases the release of CXCL8/IL-8, CCL2/MCP-1, CCL4/MIP-1β, CCL20/MIP-3α, IL-4, IL-1ra, and FGF-13 while reducing Proteinase 3 release in the anti-inflammatory-stimulated models. However, 3% honey significantly increased the release of TNF-α and CXCL8/IL-8 while reducing the release of all other analytes. We replicated a subset of the most notable findings in primary human neutrophils, and the consistent results indicate that the HL-60 data are relevant to the performance of primary cells. These findings demonstrate the variable effects of Manuka honey on the release of cytokines, chemokines, and matrix-degrading enzymes of this model of neutrophil anti-inflammatory activity. This study reinforces the importance of tailoring the concentration of Manuka honey in a wound or tissue template to elicit the desired effects during the inflammation-resolving phase of wound healing. Future in vivo investigation should be undertaken to translate these results to a physiologically-relevant wound environment.

Estevinho L, Teixeira-Santos R, G. Rodrigues A, Pina-Vaz C, Fresno JM, Tornadijo ME. Antibacterial Action Mechanisms of Honey: Physiological Effects of Avocado, Chestnut, and Polyfloral Honey upon Staphylococcus aureus and Escherichia coli

Numerous studies have explored the antibacterial properties of different types of honey from all around the world. However, the data available describing how honey acts against bacteria are few. The aim of this study was to apply a flow cytometry (FC) protocol to examine and characterize the primary effects of three varieties of honey (avocado, chestnut and polyfloral) upon physiological status of Staphylococcus aureus and Escherichia coli cells to reveal their antibacterial action mechanisms. The effects of honey samples on membrane potential, membrane integrity, and metabolic activity were assessed using different fluorochromes, in a 180 min time course assay. Time-kill experiments were also carried out under similar conditions. Exposure of S. aureus and E. coli to the distinct honey samples resulted in physiological changes related to membrane polarization and membrane integrity. Moreover, honey induced a remarkable metabolic disruption as primary physiological effect upon S. aureus. The different honey samples induced quite similar effects on both bacteria. However, the depth of bacteria response throughout the treatment varied depending on the concentration tested and among honey varieties, probably due to compositional differences in the honey.

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.

Antibacterial activity of varying UMF-graded Manuka honeys

Honey has been used as a traditional remedy for skin and soft tissue infections due to its ability to promote wound healing. Manuka honey is recognized for its unusually abundant content of the antibacterial compound, methylglyoxal (MGO). The Unique Manuka Factor (UMF) grading system reflects the MGO concentration in Manuka honey sold commercially. Our objective was to observe if UMF values correlated with the antibacterial activity of Manuka honey against a variety of pathogens purchased over the counter. The antibacterial effect of Manuka honey with UMF values of 5+, 10+, and 15+ from the same manufacturer was assessed by the broth microdilution method. Minimum inhibitory concentration (MIC) values were determined against 128 isolates from wound cultures representing gram-positive, gram-negative, drug-susceptible, and multi-drug resistant (MDR) organisms. Lower MICs were observed with UMF 5+ honey for staphylococci (n = 73, including 25 methicillin-resistant S. aureus) and Pseudomonas aeruginosa (n = 22, including 10 MDR) compared to UMF 10+ honey (p<0.05) and with UMF 10+ compared to UMF 15+ (p = 0.01). For Enterobacteriaceae (n = 33, including 14 MDR), MIC values were significantly lower for UMF 5+ or UMF 10+ compared to UMF 15+ honey (p<0.01). MIC₅₀ for UMF 5+, UMF 10+, and UMF 15+ honey against staphylococci was 6%, 7%, and 15%, and for Enterobacteriaceae was 21%, 21%, and 27%, respectively. For Pseudomonas aeruginosa MIC₅₀ was 21% and MIC₉₀ was 21–27% for all UMFs. Manuka honey exhibited antimicrobial activity against a spectrum of organisms including those with multi-drug resistance, with more potent activity overall against gram-positive than gram-negative bacteria. Manuka honey with lower UMF values, in our limited sampling, paradoxically demonstrated increased antimicrobial activity among the limited samples tested, presumably due to changes in MGO content of honey over time. The UMF value by itself may not be a reliable indicator of antibacterial effect.

Evaluation of Physiological Effects Induced by Manuka Honey Upon Staphylococcus aureus and Escherichia coli

Several studies have explored the antimicrobial properties of manuka honey (MkH). However, the data available regarding antibacterial action mechanisms are scarcer. The aim of this study was to scrutinize and characterize primary effects of manuka honey (MkH) upon the physiological status of Staphylococcus aureus and Escherichia coli (as Gram-positive and Gram-negative bacteria models, respectively), using flow cytometry (FC) to reveal its antibacterial action mechanisms. Effects of MkH on membrane potential, membrane integrity and metabolic activity were assessed using different fluorochromes in a 180 min time course assay. Time-kill experiments were carried out under the same conditions. Additionally, MkH effect on efflux pumps was also studied in an E. coli strain with an over-expression of several efflux pumps. Exposure of bacteria to MkH resulted in physiological changes related to membrane potential and membrane integrity; these effects displayed slight differences among bacteria. MkH induced a remarkable metabolic disruption as primary physiological effect upon S. aureus and was able to block efflux pump activity in a dose-dependent fashion in the E. coli strain.

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.

Anti-pseudomonad Activity of Manuka Honey and Antibiotics in a Specialized ex vivo Model Simulating Cystic Fibrosis Lung Infection

Pseudomonas aeruginosa causes problematic chronic lung infections in those suffering from cystic fibrosis. This is due to its antimicrobial resistance mechanisms and its ability to form robust biofilm communities with increased antimicrobial tolerances. Using novel antimicrobials or repurposing current ones is required in order to overcome these problems. Manuka honey is a natural antimicrobial agent that has been used for many decades in the treatment of chronic surface wounds with great success, particularly those infected with P. aeruginosa. Here we aim to determine whether the antimicrobial activity of manuka honey could potentially be repurposed to inhibit pulmonary P. aeruginosa infections using two ex vivo models. P. aeruginosa isolates (n = 28) from an international panel were tested for their susceptibility to manuka honey and clinically relevant antibiotics (ciprofloxacin, ceftazidime, and tobramycin), alone and in combination, using conventional antimicrobial susceptibility testing (AST). To increase clinical applicability, two ex vivo porcine lung (EVPL) models (using alveolar and bronchiolar tissue) were used to determine the anti-biofilm effects of manuka honey alone and in combination with antibiotics. All P. aeruginosa isolates were susceptible to manuka honey, however, varying incidences of resistance were seen against antibiotics. The combination of sub-inhibitory manuka honey and antibiotics using conventional AST had no effect on activity against the majority of isolates tested. Using the two ex vivo models, 64% (w/v) manuka honey inhibited many of the isolates where abnormally high concentrations of antibiotics could not. Typically, combinations of both manuka honey and antibiotics had increased antimicrobial activity. These results highlight the potential of manuka honey as a future antimicrobial for the treatment of pulmonary P. aeruginosa isolates, clearing potential infection reservoirs within the upper airway.

Comparison of Effectiveness of Germania Honey Compared to Manuka Honey in Methicillin-Resistant Staphylococcus aureus (MRSA) Killing

Purpose:

Manuka honey is currently used in medical-grade sterile wound treatment products and has been shown to be effective in methicillin-resistant Staphylococcus aureus (MRSA) killing in vitro and in wound healing in a number of case studies and series. Locally produced honey in Pakistan and Chile have been proposed to be as effective as Manuka honey in bacterial killing in vitro, presenting potentially more accessible and affordable alternatives. In this study, we compared the effectiveness of a local Germania honey from Saudi Arabia to Manuka honey MGO 550 for in vitro killing of MRSA.

Methodology:

Overnight Muller Hinton broth cultures of 50 wound culture isolates of MRSA from 50 patients were incubated with a series of dilutions of Manuka honey MGO 550 and corresponding Germania honey dilutions for 24 h. Turbidity was assessed to determine whether bacterial growth had occurred, and no growth was confirmed by a further 24 h sub-culture on blood agar.

Results/Key findings:

Manuka honey MGO 550 was significantly more effective than Germania honey at MRSA killing at 100% v/v, 50% v/v and 25% v/v (p=0.025, 0.000265, and 0.000112 respectively)

Conclusion:

Manuka honey MGO 550 is significantly more effective in killing MRSA in vitro than Germania honey. Germania honey does not appear to be a promising locally produced alternative to Manuka honey for the development of honey-based wound dressings. Further experiments could determine if Germania honey is effective against other bacterial species.

Antistaphylococcal and Antibiotic Resistance Modulatory Activities of Thirteen Cameroonian Edible Plants against Resistant Phenotypes

Background

In this study, 18 methanol extracts from Cameroonian edible plants were tested for their antibacterial activities against 26 strains of S. aureus; the role of efflux pumps in the resistance of tested bacteria and the antibiotic resistance-modulating activities against selected multidrug-resistant (MDR) phenotypes were also investigated.

Methods

Broth microdilution assay was used to evaluate the antibacterial activity, the role of efflux pumps, and the antibiotic resistance-modulating effects of plant extracts.

Results

Extracts from Dacryodes edulis seeds (DES) and Dacryodes edulis bark (DEB) were active against all 26 tested bacterial strains, within the minimal inhibitory concentration (MIC) range of 256–1024 µg/mL. MIC values varied from 64 to 1024 µg/mL against 96.2% of the 26 tested bacteria for Phaseolus vulgaris leaves (PVL), 92.3% for Azadirachta indica bark (AIB), Dacryodes edulis leaves (DEL), and Ricinodendron heudelotii leaves (RHL). The lowest MIC value of 64 µg/mL was obtained with the extract from Cucurbita maxima beans (CMB) against MRSA4 strain and from Uapaca guineensis bark (UGB) against MRSA9 strain. Bacterial efflux pump inhibitor (EPI), carbonyl cyanide m-chlorophenyl hydrazone (CCCP), improved the activity of DES and UGB as well as that of extracts from Hibiscus esculentus leaves (HEL) and Uapaca guineensis leaves (UGL) against resistant S. aureus strains. Antibiotic-modulating effects against more than 70% of the S. aureus strains tested were obtained when RHL (at MIC/2) was combined with CIP, ERY, and KAN (88.89%), CHL (88.89%), TET (77.78%), and STR (88.89%).

Conclusion

The present study demonstrated that the 13 tested plants had antistaphylococcal effects and that DES, HEL, UGL, and UGB could be used in combination with EPI to combat resistance to Staphylococcus aureus. Also, it demonstrated that some studied extracts and mostly RHL could be used as antibiotic resistance modulators to fight against resistant strains of S. aureus.

Comparison of the Antimicrobial Activities of Four Honeys From Three Countries (New Zealand, Cuba, and Kenya)

Skin and chronic wound infections are an increasing and urgent health problem worldwide. Their management is difficult and the development of antibiotic resistance by both planktonic and biofilm-associated bacteria necessitates the use of alternative treatments. The purpose of this study was to compare the antimicrobial activity of four honeys from different floral and geographical origins: Melipona beecheii honey (Cuba) and three Apis mellifera honeys [Manuka honey (New Zealand), A. mellifera honey (Cuba), and African honey (Kenya)]. The physicochemical parameters were within the ranges reported for these honeys and M. beecheii honey stood out due to its acidic character. An agar incorporation technique was used to determine the minimum active dilution of each honey against 52 clinical isolates (34 Gram-positive, 17 Gram-negative, and 1 Candida albicans). The antibiofilm activity of honeys was tested by assessing their ability to inhibit biofilm formation and to disrupt preformed biofilms. Overall, M. beecheii honey had the highest antimicrobial and antibiofilm activity, although a marked disruption in preformed biofilms was shared by all tested honeys. Structural changes induced by M. beecheii honey on Staphylococcus aureus and Pseudomonas aeruginosa cells were observed by transmission electron microscopy suggesting that this honey has a potent antimicrobial action and may be an excellent candidate for the development of topical preparations for the treatment of infected wounds.

Evaluation of the Antioxidant Capacity, Antimicrobial and Antiproliferative Potential of Fir (Abies alba Mill.) Honeydew Honey Collected from Gorski kotar (Croatia)

The paper examines the antiproliferative, antimicrobial and antioxidative effects of fir (Abies alba Mill.) honeydew honey from mountain region of Croatia (Gorski kotar) as a potential replacement for standard antibiotics and chemotherapeutic agents. Cell viability, annexin V assay and flow cytometry analysis served to analyse the antiproliferative effect on, apoptosis induction in and cell death of cancer cell lines: HeLa, MCF-7, SW620, CFPAC-1, MIA PaCa-2 and normal diploid human fibroblasts (BJ). Antimicrobial activity was tested against Staphylococcus and Acinetobacter strains by agar well diffusion and microdilution assays. The DPPH˙ assay determined the radical scavenging activity, while mathematical models helped to evaluate the kinetic data of DPPH˙ inhibition. Antiproliferative effect on all tested cell lines and the prominent effect on normal diploid human fibroblasts (BJ), colorectal adenocarcinoma (SW620, metastatic) and breast epithelial adenocarcinoma (MCF-7, metastatic) was observable. The mechanisms of antiproliferative effect included accumulation of cells in the sub-G1 phase in all tested cells and induction of apoptosis in SW620 and MCF-7 cells predominantly. The antibacterial assays showed that antibiotic-resistant strains of both bacteria, including multi-resistant strain A. baumannii ATCC® BAA-1605™, were sensitive to all tested honey samples. Radical scavenging assay suggests that antioxidants present in the honey possess different radical suppressing abilities and that they react at different rates with radicals, thereby causing two steps of reaction. The results of the study indicate that Croatian fir honeydew honey has a therapeutic potential due to the strong biological activity and can serve to protect human health.

Antimicrobial effect of different types of honey on Staphylococcus aureus

Honey exhibits antimicrobial activities against a wide range of bacteria in different milieu. This study aims to compare the effects of five types of honey (both imported and local Saudi honey) against Staphylococcus aureus. The five types of honey (Manuka Honey UMF +20, Manuka Honey UMF +16, Active +10 Manuka Honey, Sidr honey and Nigella sativa honey) were evaluated for their bactericidal/bacteriostatic activities against both methicillin resistant and sensitive S. aureus. The inhibitory effect of honey on bacterial growth was evident at concentrations of 20% and 10% (v/v). Manuka Honey showed the best results. Manuka Honey UMF +20 had a bactericidal effect on both methicillin resistant and sensitive S. aureus. However, Sidr and N. sativa honey exerted only a bacteriostatic effect. The efficacy of different types of honey against S. aureus was dependent on the type of honey and the concentration at which it was administered. Manuka Honey had the best bactericidal activity. Future experiments should be conducted to evaluate the effects of honey on bacterial resistance.

A Comprehensive Review of Topical Odor-Controlling Treatment Options for Chronic Wounds

The process of wound healing is often accompanied by bacterial infection or critical colonization, resulting in protracted inflammation, delayed reepithelization, and production of pungent odors. The malodor produced by these wounds may lower health-related quality of life and produce psychological discomfort and social isolation. Current management focuses on reducing bacterial activity within the wound site and absorbing malodorous gases. For example, charcoal-based materials have been incorporated into dressing for direct adsorption of the responsible gases. In addition, multiple topical agents, including silver, iodine, honey, sugar, and essential oils, have been suggested for incorporation into dressings in an attempt to control the underlying bacterial infection. This review describes options for controlling malodor in chronic wounds, the benefits and drawbacks of each topical agent, and their mode of action. We also discuss the use of subjective odor evaluation techniques to assess the efficacy of odor-controlling therapies. The perspectives of employing novel biomaterials and technologies for wound odor management are also presented.

Role of Honey in Topical and Systemic Bacterial Infections

BACKGROUND

The development of bacterial resistance to antibiotics has made it more difficult and expensive to treat infections. Honey is getting worldwide attention as a topical therapeutic agent for wound infections and potential future candidate for systemic infections.

OBJECTIVES

The purpose of this review was to summarise different antibacterial bio-active compounds in honey, their synergistic interaction and their clinical implications in topical and systemic infections. In addition, contemporary testing methods for evaluating peroxide and non-peroxide antibacterial activity of honey were also critically appraised.

DESIGN

MEDLINE, EMBASE, Cochrane Library, Pub Med, reference lists and databases were used to review the literature.

RESULTS

Honey contains several unique antibacterial components. These components are believed to act on diverse bacterial targets, are broad spectrum, operate synergistically, prevent biofilm formation, and decrease production of virulence factors. Moreover, honey has the ability to block bacterial communication (quorum sensing), and therefore, it is unlikely that bacteria develop resistance against honey. Bacterial resistance against honey has not been documented so far. Unlike conventional antibiotics, honey only targets pathogenic bacteria without disturbing the growth of normal gastrointestinal flora when taken orally. It also contains prebiotics, probiotics, and zinc and enhances the growth of beneficial gut flora. The presence of such plethora of antibacterial properties in one product makes it a promising candidate not only in wound infections but also in systemic and particularly for gastrointestinal infections. Agar diffusion assay, being used for evaluating antibacterial activity of honey, is not the most appropriate and sensitive assay as it only detects non-peroxide activity when present at a higher level. Therefore, there is a need to develop more sensitive techniques that may be capable of detecting and evaluating different important components in honey as well as their synergistic interaction.

CONCLUSIONS

Keeping in view the current guidelines for treatment of diarrhea, honey is considered one of the potential candidates for treatment of diarrhea because it contains a natural combination of probiotics, prebiotics, and zinc. Therefore, it would be worthwhile if such a combination is tested in RCTs for treatment of diarrhea.

Antibacterial Properties of Nonwoven Wound Dressings Coated with Manuka Honey or Methylglyoxal

Manuka honey (MH) is used as an antibacterial agent in bioactive wound dressings via direct impregnation onto a suitable substrate. MH provides unique antibacterial activity when compared with conventional honeys, owing partly to one of its constituents, methylglyoxal (MGO). Aiming to investigate an antibiotic-free antimicrobial strategy, we studied the antibacterial activity of both MH and MGO (at equivalent MGO concentrations) when applied as a physical coating to a nonwoven fabric wound dressing. When physically coated on to a cellulosic hydroentangled nonwoven fabric, it was found that concentrations of 0.0054 mg cm-2 of MGO in the form of MH and MGO were sufficient to achieve a 100 colony forming unit % bacteria reduction against gram-positive Staphylococcus aureus and gram-negative Klebsiella pneumoniae, based on BS EN ISO 20743:2007. A 3- to 20-fold increase in MGO concentration (0.0170-0.1 mg cm-2) was required to facilitate a good antibacterial effect (based on BS EN ISO 20645:2004) in terms of zone of inhibition and lack of growth under the sample. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) was also assessed for MGO in liquid form against three prevalent wound and healthcare-associated pathogens, i.e., Staphylococcus aureus, gram-negative Pseudomonas aeruginosa and gram-positive Enterococcus faecalis. Other than the case of MGO-containing fabrics, solutions with much higher MGO concentrations (128 mg L-1-1024 mg L-1) were required to provide either a bacteriostatic or bactericidal effect. The results presented in this study therefore demonstrate the relevance of an MGO-based coating as an environmentally friendly strategy for the design of functional dressings with antibiotic-free antimicrobial chemistries.

Preclinical development of MGO Manuka Honey microemulsion for blepharitis management

Objective

To evaluate the in vitro antimicrobial effects of cyclodextrin-complexed and uncomplexed Manuka honey on bacteria commonly associated with blepharitis, and in vivo rabbit eye tolerability of a cyclodextrin-complexed methylglyoxal (MGO) Manuka Honey microemulsion (MHME).

Methods and analysis

In vitro phase: Bacterial growth inhibition was assessed by area under the growth curve (AUC) for Staphylococcus aureus, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for S. aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa with cyclodextrin-complexed and uncomplexed Manuka honey were determined.

In vivo phase: Six rabbits were administered 20 µL of MHME (at 1:10 dilution) to the right eye (treated) and 20 µL of saline to the left eye (control) daily, for 5 days. Tear evaporation, production, osmolarity, lipid layer, conjunctival hyperaemia and fluorescein staining were assessed daily, before and 15 min after instillation.

Results

In vitro phase: The relative AUC for cyclodextrin-complexed Manuka honey was lower than that of uncomplexed honey at both 250 and 550 mg/kg of MGO (both p <0.05). Cyclodextrin-complexed honey had lower MIC and MBC than uncomplexed honey for both S. aureus and S. epidermidis, but not P. aeruginosa.

In vivo phase: No significant changes were observed in the parameters assessed in either treated or control eyes (all p >0.05).

Conclusion

Overall, antimicrobial potency of cyclodextrin-complexed Manuka honey was greater than uncomplexed honey. No significant immediate or cumulative adverse effects were observed with MHME application on rabbit eyes, supporting future conduct of clinical safety and tolerability trials in human subjects.

Antimicrobial ceragenins inhibit biofilms and affect mammalian cell viability and migration in vitro

The healing of burn wounds is often hampered by bacterial infection and the formation of biofilms. Antimicrobial peptides (AMPs) are effective in promoting wound healing, but are susceptible to degradation. We have tested the ability of ceragenins (CSAs), mimics of antimicrobial peptides, to mitigate preformed biofilms and stimulate wound healing in vitro. Potent CSAs (MICs < 10 μg·mL⁻¹) were tested against biofilms formed from a mixture of Pseudomonas aeruginosa and Staphylococcus aureus grown for 22 h and subjected to 20 h treatment. Many CSAs showed more potent anti‐biofilm activity than the endogenous AMP LL‐37, and CSA‐13 and CSA‐90 decreased the amount of biofilm matrix substances detected by SYPRO Ruby stain. Effects on mammalian cells were measured by viability, migration, and tube formation assays in vitro. Although CSAs were toxic to immortalized human keratinocytes (HaCaTs) at higher concentrations (>10 μg·mL⁻¹), lower concentrations of CSA‐13 and CSA‐192 stimulated cell migration. CSA‐13, CSA‐90, and CSA‐142 also stimulated tube formation in an in vitro angiogenesis model. An inhibitor of vascular endothelial growth factor receptor 2 (VEGFR2) blocked tube formation stimulated by CSA‐13, suggesting that CSA‐13 signals through this receptor. Ceragenins display anti‐biofilm activity and stimulate migration and tube formation in vitro. This work suggests that ceragenins have the potential to be both topical antimicrobials and wound‐healing adjunct therapeutics.

In Vitro Evaluations and In Vivo Toxicity and Efficacy Studies of MFM501 against MRSA

Previously we have discovered a synthetically derived pyrrolidone alkaloid, MFM501, exhibiting good inhibitory activity against 53 MRSA and MSSA isolates with low cytotoxicity against three normal cell-lines with IC₅₀ values at >625 µg/ml. Time-kill assay, scanning electron microscopy (SEM) analysis, in vivo oral acute toxicity test, and mice peritonitis model were carried out in this study. In the time-kill study, MFM501 showed a less than 3 log₁₀ decrease in bacterial colony concentration value (CFU/ml) which represented a bacteriostatic action while displaying a time-dependent inhibitory mechanism. Following that, SEM analysis suggested that MFM501 may exert its inhibitory activity via cytoplasmic membrane disruption. Moreover, MFM501 showed no toxicity effect on treated mice at an estimated median acute lethal dose (LD₅₀) value of more than 300 mg/kg and less than 2000 mg/kg. For the efficacy test, a mean effective dose (ED₅₀) of 87.16 mg/kg was obtained via a single dose oral administration. Our data demonstrated that MFM501 has the potential to be developed further as a new, safe, and effective oral-delivered antibacterial agent against MRSA isolates.

In-vitro susceptibility of methicillin-resistant Stayphylococcus aureus to honey

Wound infections caused by methicillin-resistant Staphylococcus aureus (MRSA) is becoming much complicated and costly to treat as antimicrobial resistance is quite common. Twenty five MRSA strains isolated from infected wounds and three ATCC reference strains were evaluated for their susceptibility to locally produced black seed (Nigella sativa), beri (ZiziphusJujuba) and shain honey (Plectranthus rugosus wall) by agar incorporation assay. Medically graded manuka honey (UMF 21⁺) was included as control. Locally produced black seed honey inhibited all clinical isolates at mean MIC of 5.5% (v/v), whereas manuka honey at mean MIC of 4.4% (v/v). The other two locally produced honey; beri and shain honey inhibited these isolates at 6.4% and 10.4% (v/v) respectively. The result of the study has demonstrated that indigenous black seed honey has comparable antibacterial activity to manuka honey and thus offers a good new addition to the existing honey resource for the treatment of wound infections.

Honey is potentially effective in the treatment of atopic dermatitis: Clinical and mechanistic studies

Introduction

As manuka honey (MH) exhibits immunoregulatory and anti‐staphylococcal activities, we aimed to investigate if it could be effective in the treatment of atopic dermatitis (AD).

Methods

Adult volunteers with bilateral AD lesions were asked to apply MH on one site overnight for seven consecutive days and leave the contralateral site untreated as possible. Three Item Severity score was used to evaluate the response. Skin swabs were obtained from both sites before and after treatment to investigate the presence of staphylococci and enterotoxin production. In addition, the ability of MH and its methanolic and hexane extracts to down regulate IL4‐induced CCL26 protein release from HaCaT cells was evaluated by enzyme linked immunosorbent assay. Also, the ability of MH to modulate calcium ionophore‐induced mast cell degranulation was assessed by enzyme immunoassay.

Results

In 14 patients, AD lesions significantly improved post MH treatment versus pre‐treatment as compared to control lesions. No significant changes in the skin staphylococci were observed after day 7, irrespective of honey treatment. Consistent with the clinical observation, MH significantly down regulated IL4‐induced CCL26 release from HaCaT cells in a dose‐dependent manner. This effect was partially lost, though remained significant, when methanolic and hexane extracts of MH were utilized. In addition, mast cell degranulation was significantly inhibited following treatment with MH.

Conclusions

MH is potentially effective in the treatment of AD lesions based on both clinical and cellular studies through different mechanisms. This needs to be confirmed by randomized and controlled clinical trials.

A Comparison of Tissue Engineering Scaffolds Incorporated with Manuka Honey of Varying UMF

Purpose. Manuka honey (MH) is an antibacterial agent specific to the islands of New Zealand containing both hydrogen peroxide and a Unique Manuka Factor (UMF). Although the antibacterial properties of MH have been studied, the effect of varying UMF of MH incorporated into tissue engineered scaffolds have not. Therefore, this study was designed to compare silk fibroin cryogels and electrospun scaffolds incorporated with a 5% MH concentration of various UMF. Methods. Characteristics such as porosity, bacterial clearance and adhesion, and cytotoxicity were compared. Results. Pore diameters for all cryogels were between 51 and 60 µm, while electrospun scaffolds were 10 µm. Cryogels of varying UMF displayed clearance of approximately 0.16 cm for E. coli and S. aureus. In comparison, the electrospun scaffolds clearance ranged between 0.5 and 1 cm. A glucose release of 0.5 mg/mL was observed for the first 24 hours by all scaffolds, regardless of UMF. With respect to cytotoxicity, neither scaffold caused the cell number to drop below 20,000. Conclusions. Overall, when comparing the effects of the various UMF within the two scaffolds, no significant differences were observed. This suggests that the fabricated scaffolds in this study displayed similar bacterial effects regardless of the UMF value.

Novel assay of antibacterial components in manuka honey using lucigenin-chemiluminescence-HPLC

Five components (hydrogen peroxide, methylglyoxal, dihydroxyacetone, fructose and glucose) of New Zealand manuka honey (Leptospermum scoparium) were analyzed using lucigenin chemiluminescence high-performance liquid chromatography (lucigenin-CL-HPLC). We focused on active oxygen species produced from the components in order to easily detect these five components contained in manuka honey. H₂O₂ and O₂^- generated from these components were identified by lucigenin-CL and electron spin resonance (ESR), and the bactericidal effect of ROS was confirmed using E. coli. The previously reported assays for Manuka honey components have low specificities and require complicated preprocessing methods. As our results, the detection and identification of these components were possible within 30 min in lucigenin-CL-HPLC system, without any special treatment. It is considered that lucigenin-CL-HPLC is useful for the quality control and the analysis of various honey.

Effect of United States buckwheat honey on antibiotic-resistant hospital acquired pathogens

INTRODUCTION

Due to an upsurge in antibiotic-resistant infections and lack of therapeutic options, new approaches are needed for treatment. Honey may be one such potential therapeutic option. We investigated the susceptibility of hospital acquired pathogens to four honeys from Wisconsin, United States, and then determined if the antibacterial effect of each honey against these pathogens is primarily due to the high sugar content.

METHODS

Thirteen pathogens including: four Clostridium difficile, two Methicillin-resistant Staphylococcus aureus, two Pseudomonas aeruginosa, one Methicillin-Susceptible Staphylococcus aureus, two Vancomycin-resistance Enterococcus, one Enterococcus faecalis and one Klebsiella pneumoniae were exposed to 1-50% (w/v) four Wisconsin honeys and Artificial honey to determine their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using the broth dilution method.

RESULTS

Buckwheat honey predominantly exhibited a bactericidal mode of action against the tested pathogens, and this varied with each pathogen. C. difficile isolates were more sensitive to the Wisconsin buckwheat honey as compared to the other pathogens. Artificial honey at 50% (w/v) failed to kill any of the pathogens. The high sugar content of Wisconsin buckwheat honey is not the only factor responsible for its bactericidal activity.

CONCLUSION

Wisconsin buckwheat honey has the potential to be an important addition to therapeutic armamentarium against resistant pathogens and should be investigated further.