The honeybee (Apis mellifera) produces honey by collecting and modifying nectar from local flowers [2]. It is inexpensive and simple to obtain, but various types are available, depending on the plant source (i.e., Manuka, Kanuka, Sidr, clover). The full therapeutic effect of medicinal honeys has not been fully elucidated; however, many properties have been identified that are potentially antibacterial in effect. Honey is a supersaturated sugar solution, with a high osmolarity and a low pH, and can create hydrogen peroxide via endogenous glucose oxidase activity [3]. Manuka honey is produced in New Zealand and is derived from the Manuka plant (Leptospermum scoparium). The phenol compound methylglyoxal (MGO) has been implicated as a major bactericidal compound in Manuka honey. MGO is cytotoxic and is produced chiefly in glycolysis. These qualities provide an adverse environment for bacterial growth [3]. Manuka honey has been shown to prevent and disrupt preexistent biofilms and is effective against planktonic bacteria and yeast. Honey has also been shown to stimulate the immune system as well as promote wound healing [3]. Lu et al. evaluated the effect of Manuka, Kanuka, and clover honeys against four strains of bacteria, including S. aureus and P. aeruginosa. Manuka honey, with the highest concentration of endogenous MGO, was the most effective strain in slowing bacterial growth. When catalase was added to the honeys, rendering the hydrogen peroxide inactive, Manuka honey (with its high concentration of MGO) still resulted in the greatest inhibition of bacterial growth. Even if hydrogen peroxide and MGO were neutralized, the honeys still maintained their growth inhibitory effect, suggesting the presence of other antibacterial compounds besides hydrogen peroxide and MGO [3].

Jervis-Bardy et al. evaluated the effect of the MGO present in Manuka honey in an in vitro system. They found that honey with endogenous MGO was bactericidal to four strains of S. aureus biofilms and honey without endogenous MGO was not. Exogenous MGO alone or in combination with a non-MGO honey reinstituted bactericidal activity [4]. This suggests that naturally occurring MGO in the Manuka honey is the cause of the bactericidal effect on biofilm-forming S. aureus. Some Manuka/Kanuka blends of honey have endogenous MGO; however, Kanuka honey has very low levels [2]. The presence of endogenous MGO in Manuka suggests why this honey has been found to have superior antibacterial properties to others [5].

Manuka honey can be considered for use in patients with CRS that continue to have symptoms despite maximal traditional antibacterial and surgical therapy, especially when attributed to biofilm-producing bacteria.

The inflammation from CRS may be directly or indirectly caused by the body’s host response to bacterial infection. Biofilms have been implicated as a causative and complicating factor of CRS management. Typically biofilms are difficult to treat with traditional medical and surgical methods. Alandejani et al. evaluated the effect of various honeys, including gamma-irradiated Manuka, in the treatment of biofilm-producing Pseudomonas aeruginosa and Staphylococcus aureus in vitro. Gamma-irradiation was performed to ensure sterility. Manuka honey was found to be bactericidal to 82 % of MSSA biofilms, 63 % of MRSA biofilms, and 91 % of Pseudomonas [5]. Manuka honey was found to be superior in this study to traditional antibiotic therapy in the treatment of biofilm-producing MSSA, MRSA, and Pseudomonas. Rifampin was the only antibiotic of those tested that had bactericidal activity against the biofilms (only to 18 % of the strains however) [5].

Kilty et al. treated nasal mucosa with Manuka honey once daily in one of the nasal cavities of rabbits and used the other nasal cavity as a control. Light and transmission electron microscopy revealed no epithelial damage. Mouse trachea was used to evaluate Manuka honey’s effect on ciliary beat frequency and was found to not alter motility of cilia. When the olfactory mucosa was examined, there was a higher rate of cell proliferation in the epithelium (as measured by Ki-67 staining) when samples treated with Manuka honey were compared to control, suggesting olfactory injury [6]. Paramasivan et al. used a sheep model to evaluate the efficacy of Manuka honey with varying concentrations of MGO. They found that increasing MGO levels resulted in a dose-related decrease in S. aureus biofilm levels. At MGO concentrations of 3.6 mg/ml, there was loss of cilia seen on scanning electron microscopy (SEM). At 7.2 mg/ml of MGO, the sinus mucosa appeared grossly inflamed and demonstrated squamous metaplasia on light microscopy. Furthermore, ciliary denudation and cellular detachment were seen on electron microscopy [7].

A Cochrane review of the use of honey in wound care and burns found that honey may shorten healing times for moderate burns when compared with conventional dressings. Honey was not found to improve healing of chronic venous ulcers and may delay healing in deep burns [2

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