Manuka-type honeys can eradicate biofilms produced by
Staphylococcus aureus strains with different biofilm-forming abilities
PeerJ 2014 Mar 25;2:e326
Chronic wounds are a major global health problem. Their
management is difficult and costly, and the development of antibiotic
resistance by both planktonic and biofilm-associated bacteria necessitates the
use of alternative wound treatments. Honey is now being revisited as an
alternative treatment due to its broad-spectrum antibacterial activity and the
inability of bacteria to develop resistance to it. Many previous antibacterial
studies have used honeys that are not well characterized, even in terms of
quantifying the levels of the major antibacterial components present, making it
difficult to build an evidence base for the efficacy of honey as an antibiofilm
agent in chronic wound treatment. Here we show that a range of
well-characterized New Zealand manuka-type honeys, in which two principle
antibacterial components, methylglyoxal and hydrogen peroxide, were quantified,
can eradicate biofilms of a range of Staphylococcus aureus strains that differ
widely in their biofilm-forming abilities. Using crystal violet and viability
assays, along with confocal laser scanning imaging, we demonstrate that in all
S. aureus strains, including methicillin-resistant strains, the manuka-type
honeys showed significantly higher anti-biofilm activity than clover honey and
an isotonic sugar solution.
We observed higher anti-biofilm activity as the
proportion of manuka-derived honey, and thus methylglyoxal, in a honey blend
increased. However, methylglyoxal on its own, or with sugar, was not able to
effectively eradicate S. aureus biofilms. We also demonstrate that honey was
able to penetrate through the biofilm matrix and kill the embedded cells in
some cases. As has been reported for antibiotics, sub-inhibitory concentrations
of honey improved biofilm formation by some S. aureus strains, however, biofilm
cell suspensions recovered after honey treatment did not develop resistance
towards manuka-type honeys. New Zealand manuka-type honeys, at the
concentrations they can be applied in wound dressings are highly active in both
preventing S. aureus biofilm formation and in their eradication, and do not
result in bacteria becoming resistant. Methylglyoxal requires other components
in manuka-type honeys for this anti-biofilm activity.
Our findings support the
use of well-defined manuka-type honeys as a topical anti-biofilm treatment for
the effective management of wound healing.
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