A Comparison Between Medical Grade Honey and Table Honeys in Relation to Antimicrobial Efficacy

Rose A. Cooper, PhD; Leighton Jenkins, BSc

Disclosures

Wounds. 2009;21(2) 

In This Article

Abstract and Introduction

Abstract

When antimicrobial agents are being evaluated prior to their introduction into clinical practice, advance publicity may interest potential users but access to that agent will normally be limited until licensed products are released and distributed. Honey is an ancient therapy that has recently been re-introduced into modern medicine. Medical grade honey (MGH) is being incorporated into sterile devices that are applied topically to wounds. Honey is universally recognized and it is readily accessible. Patients and practitioners may, therefore, consider using table honey from supermarkets as a cheap, readily available alternative to more expensive, regulated, honey-based wound care products. This study was designed to compare the antibacterial potency and microbial flora of 18 table honeys to a representative sample of Leptospermum honey (a MGH). Standardized tests of microbial content and in-vitro efficacy were conducted for each sample. Table honeys generally possessed lower antibacterial activity than the MGH and contained a wide range of microbial species, whereas MGH was sterile. The disadvantages of using non-sterile table honeys in medical practice were reviewed. Results suggest the need for randomized clinical trials verifying the efficacy and/or safety of any form of honey used in topical wound care.

Introduction

The development of a new antibiotic usually takes between 10 and 15 years and costs nearly $1 billion. During that time, a code number or trivial name that is meaningless to those not involved in its development identifies the agent. Although preliminary reports of its efficacy may excite potential patients, their access to the new treatment will be restricted until the launch and distribution of the fully developed and licensed product. Less expensive alternatives may not be available immediately since the bioactive component(s) may be patent protected.

Honey is a broad-spectrum antimicrobial agent that has been used in treating wounds for thousands of years. It has been shown to inhibit the growth of a wide range of bacteria, fungi, protozoa, and viruses.[1,2] Laboratory tests with medical grade honeys (MGH), particularly Leptospermum honeys such as manuka or jellybush, have demonstrated that antibiotic-sensitive bacteria and antibiotic-resistant bacteria are equally susceptible to dilute concentrations.[3,4,5,6] An increasing number of reports of the eradication of methicillin-resistant Staphylococcus aureus (MRSA) from wounds illustrate the clinical efficacy of such honeys.[7,8,9,10,11]

All honeys have a high sugar content, low water content, and acidity that prevents microbial growth. Most unprocessed honeys, when diluted slowly, generate hydrogen peroxide due to the activation of the enzyme glucose oxidase, which oxidizes glucose to gluconic acid and hydrogen peroxide.[12,13] Hydrogen peroxide has antibacterial properties, but not all honeys exhibit equal activity.[1]

In many honeys, heating at elevated temperatures destroys this peroxide activity and it is lost in the presence of catalase (an enzyme that degrades hydrogen peroxide and is present in wound fluid). However, Leptospermum honeys retain activity in the presence of catalase and are known as non-peroxide honeys.[1] Contributions to the non-peroxide activity of Leptospermum honey by several components have been identified,[14,15,16,17] but it is most likely that more have yet to be characterized.

An in-vitro bioassay using S aureus allows the estimation of the antibacterial potency of honeys in relation to a solution of phenol.[18] Total activity (peroxide and non-peroxide) is estimated by dilution of honey in water; non-peroxide activity is estimated by dilution in catalase.

Honey largely disappeared from conventional medical practice during the 1970s,[19] but was recently reintroduced into modern wound care through the development of sterile devices utilizing MGH. In Australia, the Therapeutic Goods Association licensed sterile MGH for wound care in 1999; the first MGH-impregnated dressing was licensed in the United Kingdom in 2004. A range of products is currently available throughout Europe and Australasia, and some are available in Canada and the United States. Medical journal studies reporting that difficult wounds treated successfully with prototype wound care products[7,8,20,21] generated significant media and public interest in honey as a wound therapy in the United Kingdom, which prompted prospective patients to apply non-sterile honeys obtained from supermarkets and health stores to their chronic wounds. To date, no adverse events are known to have resulted from this manner of use, however, the possible presence of clostridial spores in such products cannot be ignored.[22] While MGH is selected and processed to minimize adverse clinical events,[23] honey intended for culinary use is not. This study was, therefore, designed to investigate the antibacterial potency and microbial flora of a selection of table honeys and one MGH to explore their therapeutic potential and safety.

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