Antimicrobial activity of organic honeys against food pathogenic bacterium Clostridium perfringens

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.

ε-Polylysine Derived from Marine Bacteria-A Possible Natural Preservative for Raw Milk Storage

Despite the fact that researchers have been working on the preservation of raw milk at room temperature for several decades, most of the processes are limited to the use of chemical preservatives. One of the major problems of raw milk self-life is its spoilage at ambient temperature during the summer season. Therefore, in the present study, research has been conducted to control raw milk spoilage at 4 °C and 35 °C (considered in different regions’ ambient temperatures). ε-Polylysine, a natural preservative approved for food use, was isolated from the fermentation broth of Bacillus licheniformis PL26 grown in an M3G medium, and its antimicrobial preservation properties for milk applications were tested. The raw milk samples containing 0.02% w/v ε-polylysine could be stored at 4 °C for up to 16 days without spoilage, however, raw milk samples without ε-polylysine as preservative spoiled on the 8th day even at 4 °C refrigeration conditions. Raw milk containing 0.02% ε-polylysine in combination with 0.2% sodium bicarbonate (added to avoid acidification) could be stored at ambient temperature (35 °C) for up to 48 h. The changes in milk composition, especially of the casein, lactose, and fat stability, during storage under different conditions with/without ε-polylysine, were studied as well. The present study proves that ε-polylysine can be successfully used as a new biopreservative. Therefore, for the dairy industry, a natural preservative to store milk at room temperature during the summer season, replacing synthetic preservatives derived from renewable sources, can be proposed. Once again, marine bacteria seem to be one of the promising sustainable and renewable sources of biologically active compounds such as new food biopreservatives

Diversity and biopotential of Bacillus velezensis strains A6 and P42 against rice blast and bacterial blight of pomegranate

Bacillus velezensis is widely known for its inherent biosynthetic potential to produce a wide range of bio-macromolecules and secondary metabolites, including polyketides (PKs) and siderophores, as well as ribosomally and non-ribosomally synthesized peptides. In the present study, we aimed to investigate the bio-macromolecules, such as proteins and peptides of Bacillus velezensis strains, namely A6 and P42 by whole-cell sequencing and highlighted the potential application in controlling phytopathogens. The bioactive compounds, specifically secondary metabolites, were characterized by whole-cell protein profiling, Thin-Layer Chromatography, Infra-Red Spectroscopy, Nuclear Magnetic Resonance, Gas Chromatograph and Electro Spray Liquid Chromatography. Gas Chromatography analysis revealed that the A6 and P42 strains exert different functional groups of compounds, such as aromatic ring, aliphatic, alkene, ketone, amine groups and carboxylic acid. Whole-cell protein profiling of A6 and P42 strains of B. velezensis by nano-ESI LC-MS/MS revealed the presence of 945 and 5303 proteins, respectively. The in vitro evaluation of crude extracts (10%) of A6 and P42 significantly inhibited the rice pathogen, Magnaporthe oryzae (MG01), whereas the cell-free culture filtrate (75%) of strain P42 showed 58.97% inhibition. Similarly, in vitro evaluation of crude extract (10%) of P42 strain inhibited bacterial blight of pomegranate pathogen, Xanthomonas axonopodis pv. punicae, which eventually resulted in a higher inhibition zone of 3 cm, whereas the cell-free extract (75%) of the same strain significantly suppressed the growth of the pathogen with an inhibition zone of 1.48 cm. From the results obtained, the crude secondary metabolites and cell-free filtrates (containing bio-macromolecules) of the strains A6 and P42 of B. velezensis can be employed for controlling the bacterial and fungal pathogens of crop plants.

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.

Synergistic Antimicrobial Interaction between Honey and Phage against Escherichia coli Biofilms

Chronic wounds afford a hostile environment of damaged tissues that allow bacterial proliferation and further wound colonization. Escherichia coli is among the most common colonizers of infected wounds and it is a prolific biofilm former. Living in biofilm communities, cells are protected, become more difficult to control and eradicate, and less susceptible to antibiotic therapy. This work presents insights into the proceedings triggering E. coli biofilm control with phage, honey, and their combination, achieved through standard antimicrobial activity assays, zeta potential and flow cytometry studies and further visual insights sought by scanning electron microscopy and transmission electron microscopy. Two Portuguese honeys (PF2 and U3) with different floral origin and an E. coli-specific phage (EC3a), possessing depolymerase activity, were tested against 24- and 48-h-old biofilms. Synergic and additive effects were perceived in some phage-honey experiments. Combined therapy prompted similar phenomena in biofilm cells, visualized by electron microscopy, as the individual treatments. Honey caused minor membrane perturbations to complete collapse and consequent discharge of cytoplasmic content, and phage completely destroyed cells leaving only vesicle-like structures and debris. Our experiments show that the addition of phage to low honey concentrations is advantageous, and that even fourfold diluted honey combined with phage, presents no loss of antibacterial activity toward E. coli. Portuguese honeys possess excellent antibiofilm activity and may be potential alternative therapeutic agents in biofilm-related wound infection. Furthermore, to our knowledge this is the first study that assessed the impacts of phage-honey combinations in bacterial cells. The synergistic effect obtained was shown to be promising, since the antiviral effect of honey limits the emergence of phage resistant phenotypes.

Screening bioactivity and bioactive constituents of Nordic unifloral honeys

The objective of this study was to screen the antibacterial and antioxidant activity of thirty nine honey samples from Finland, Sweden, Norway and Denmark. Their physicochemical properties were analysed, antioxidant activity was evaluated by DPPH assay and antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus was assessed by microdilution assay. The honey samples obtained were buckwheat, caraway, clover, dandelion, fireweed, heather, lime tree, lingonberry, rape, raspberry, sweet clover, willow, mire, honeydew and polyfloral. Eleven honey samples showed high antioxidant activity. With 15% honey dilution, three unifloral honeys had over 85% inhibition against growth of P. aeruginosa and ten honey samples against S. aureus. The buckwheat, raspberry and honeydew honeys showed the highest antibacterial and antioxidant activity. An unexpectedly high amount of methylglyoxal was found in mire and forest honeys. Some phenolic compounds are shown to be plant species-specific floral markers due to their appearance in specific unifloral honey samples.