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

Discussion

Ancient physicians were selective in which honeys they included in their remedies. Variations in samples intended for wound care have been discussed,[24] but comparative clinical studies to investigate differential healing characteristics have yet to be attempted. The data generated in this study clearly demonstrates the range of antibacterial activity associated with different honeys and illustrates the importance of selecting honey of high potency when the causative agents of wound infection are to be inhibited. Ten of the honey samples failed to demonstrate antibacterial activity in the bioassay, and of the 9 active honeys, the MGH tested here was a non-peroxide honey with the highest level of antibacterial activity. Peroxide generating honeys are likely to be inactivated in vivo since human cells and erythrocytes contain catalase, but Leptospermum honeys would not be inactivated because their non-peroxide antibacterial activity depends on a mixture of components other than hydrogen peroxide.

Jars of Leptospermum honey labeled with inflated antibacterial potency and marketed to the public is an emerging problem in the United Kingdom. The purchase price of such honeys (manuka from New Zealand and jellybush from Australia) depends on non-peroxide antibacterial activity, which is normally tested in registered laboratories before being exported. Some traders seem to have misled the public. Honeys with proven antibacterial potency (10+) have been recommended for wound care preferentially over honeys of low or unknown potency.[25] The quality of components used in the manufacture of licensed wound care products is assured by validated tests and regulated by authoritative bodies. This ensures the batch-to-batch consistency expected of medical products. Supermarket honey, however, does not undergo such rigorous controls. The therapeutic benefits of honey have been identified as the ability to stimulate rapid wound healing and the inhibition of wound pathogens.[25,26] It seems logical to select honeys with high antibacterial potency for topical application to wounds rather than those at low or undetectable levels. Of the honeys tested here, the MGH was found to possess the greatest bactericidal activity. Clinical trials designed to evaluate the relative antimicrobial efficacy of different MGHs have not yet been executed.

The presence of microorganisms in raw honeys is not unexpected and routes for the contamination of honeys are understood.[26] The sample with the highest count of mesophilic aerobic bacilli was sample 15, otherwise counts did not exceeded 1000 cfu/g. None of the honeys tested contained coliforms or salmonellae and Clostridium botulinum was not detected. The cohort of honeys tested here was small and most likely explains why Cl botulinum was not isolated. Prevalence of spores of Cl botulinum ranges between 2% and 24% of honeys[22] and is the reason that honey is not fed to infants younger than 12 months. Wound botulism is rare and usually arises from the use of recreational drugs, but the possibility of acquiring this infection by the topical use of unsterile honey should not be dismissed.

The aerobic spore-bearing bacterial species characterized were not overt pathogens, but some (Bacillus brevis, Bacillus coagulans, Bacillus licheniformis, Bacillus pumilus, and Bacillus subtilis) have been isolated on infrequent occasions from debilitated patients. One (Bacillus cereus) has been associated rather more frequently with infections such as abscesses, bacteremia, septicemia, burn cellulitis, osteomyelitis, and postoperative infections.[28] Bacillus capillosus has been isolated from the intestinal contents of animals and birds.[29]

Honey is not normally collected from infected hives, but the isolation of Paenibacillus alvei from 4 samples (8, 9, 10, and 15) suggests that honey had been collected from unhealthy hives because this bacterium is often recovered from diseased honeybee larvae obtained from colonies infected with European foulbrood disease (EFB).[30] One consequence of beehive infection is treatment with antibiotics and the contamination of honey collected from such treated hives. MGHs should therefore be screened to assure the absence of contaminating antibiotics.[23]

The presence of Paenibacillus alvei on plates caused some difficulties in the laboratory during the isolation of bacteria from honey samples as it swarmed across agar plates sometimes contaminating single colonies before they were subcultured to fresh plates. It is possible that species have not been successfully isolated because of this issue.

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