Effect of innate honey components on microbial stress. Understanding the mechanism of honey antibacterial action against anaerobe bacteria associated

Lead Research Organisation: University of Birmingham
Department Name: Sch of Biosciences

Abstract

Honey has a long history in wound treatment, proved to have therapeutic properties mainly attributed to the enzymatic production of hydrogen peroxide (H2O2), high osmolality, low pH (3.2-4.5) and also the contribution of other innate antibacterial compounds. After the availability of medical grade honeys (Manuka, Medihoney, Surgihoney, Remavil) on the market, honey garnered renewed interest in its clinical potential as it was reported to have antibacterial/ bactericidal activity against a wide range of clinical important pathogens. The investigation of the underlying antimicrobial mechanism of honey, being still obscure, constitutes the aim of this study. A model- honey, which performs high antibacterial activity, will be developed and optimized, so as to be characterized the antibacterial mechanism against E.coli strains associated with vaginal infection. Further hypothesis concern the potential synergistic effect of honey and Lactobacilli, which produce H2O2, inhibiting the colonization of anaerobes (and facultative anaerobes) in the vagina. The effect of individual and synergistic stress (pH, osmolality, H2O2) on bacteria responses will be investigated with applied microbiology and molecular biology. Microscopy techniques will elucidate the effect of multiple stresses on bacteria phenotype changes. Mathematical models will support the prediction of bacterial responses. Ultimately, the systematic understanding of honey antibacterial action and the underlying molecular mechanism on bacterial stress responses is pivotal for the development of an innovative pharmaceutical application. This promising technology is based on the controlled release mechanism of honey antibacterial components intravaginally, eliminating pathogens' colonization and maintaining the microflora in desirable levels.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
BB/M01116X/1 01/10/2015 30/09/2023
1644039 Studentship BB/M01116X/1 05/10/2015 30/09/2019 Maria Masoura
 
Description The aim of this study is to investigate the antibacterial mechanism of honey. Based on previous findings the antibacterial activity of honey is varied a lot between honey types and their capacity to produce hydrogen peroxide upon its dilution. The enzymatic bio-products from this reaction; hydrogen peroxide and gluconic acid, are thought to be in the first line of this activity but the underlying antibacterial mechanism has not been yet investigated. The novelty of our approach was to explain the antibacterial mechanism of honey using a model system that selectively combines some of those components in couples or all together. One of the main outcomes though this investigation is that the synergism of those components found in model closely simulates the killing effect of real honey against bacteria tested. Moreover, the presence of sugars in the system could contribute synergistically causing an osmotic effect and their absence accelerates the killing effect in a way that does not follow this of real honey. The contribution of hydrogen peroxide was verified by testing the sensitivity of E. coli strains with limited defence to oxidative stress against the wild type. Those results show a strong dependence of honey's effect from hydrogen peroxide. A molecular approach on bacterial responses to the model and real honey is to further elucidate the underlying mechanism.
Moreover, Transposon Insertion Sequence (TraDIS) method was used in order to identify the targets of honey in molecular level. This analysis (which is still under process) indicated a banch of genes associated to acid, oxidative stress, membrane function and metabolic activities being targetef from the modle honey we applied. This is yet to be confirmed by testing the susceptibility of the respective mutants to model honey or/ and individual compounds of the model compared to the WT.
Moreover, a vaginal model as was described elsewhere was infected by E.coli and C.albicans in order to represent a bacterial vaginosis. then the effect of model honey and real honey was tested against the infected model. The survival modes of each isolates was tested, while flow cytometry and fluorescence microscopy were used in order to see the effect of honey in single cell level and monitor the infection in days intervals respectively. E.coli found to be significantly susceptible to honey being in a mix infected system, than growing alone. In the opposite C.albicans found to be partially affected and then restoring its metabolic growth.
Exploitation Route The explanation of antibacterial mechanism in honey is to contribute a lot to the development of novel medical and cosmetic products. The limitation in the knowledge on the potential of honey as an antibiotic and the discovery of certain compounds that contribute more to its activity results in a saturated market of honey products oriented to a certain use. The characterization of antibacterial mechanism could enhance the massive production of certain types of honey or engineered honey formulations. Moreover, the extensive studies against multiresistant strains is to lead the way for honey as an alternative natural based antibiotic.
Sectors Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology