Manuka honey chelates iron and impacts iron regulation in key bacterial pathogens

Abstract

Aim The aim of this study was to test the hypothesis that Manuka honey (MH) chelates iron and promotes an iron‐limiting environment, which contributes to its antimicrobial activity. Methods and Results Employing a ferrozine‐based assay, we observed that MH is an iron chelator that depletes iron from solution. Siderophores are small molecules that bind ferric iron (III) with high affinity and their levels are upregulated by bacteria under iron‐limiting conditions. We demonstrated by quantitating siderophore production that Escherichia coli and Pseudomonas aeruginosa treated with MH sub‐minimum inhibitory concentrations (sub‐MIC) experience an iron‐limiting environment and increase siderophore production. In addition, supplementation with ferrous iron (II) significantly increased growth of E. coli, Staphylococcus aureus and P. aeruginosa cultured at their MH MIC above that observed in nonsupplemented controls. By contrast, supplementation with ferric iron (III) significantly increased growth for only E. coli and P. aeruginosa, above their nonsupplemented controls. Conclusions Manuka honey chelates iron, thereby generating an iron‐limiting environment for E. coli and P. aeruginosa, and to a lesser extent S. aureus, which contributes to its antimicrobial properties. Significance and Impact of the Study Our work demonstrates that MH‐induced iron chelation is an antimicrobial mechanism that differentially impacts the bacterial species tested here. Iron chelation affects multiple diverse physiological processes in bacteria and would contribute to the lack of bacterial resistance to MH. Iron metabolism is tightly regulated; bacteria require this essential nutrient for survival, but in excess it is toxic. Additional exploration of MH’s iron chelation mechanism will facilitate its future use in mainstream medicine.

Honey: Another Alternative in the Fight against Antibiotic-Resistant Bacteria?

“…Moreover, other underlying mechanisms could also affect bacterial metabolism. Studies on E. coli [74,75], as well as on P. aeruginosa [75,76] and S. aureus [75], confirmed the effect of manuka honey as an iron-chelator, generating a limiting environment of this element, which is essential for bacterial metabolism and survival. Furthermore, membrane potential is also a fundamental process in energy generation for bacteria.…”

Iron Pathways and Iron Chelation Approaches in Viral, Microbial, and Fungal Infections

“…Manuka honey, produced from the nectar of Leptospermum scoparium (manuka bush), was discovered to elicit anti-microbial activity against multiple pathogens [ 116 ]. Specifically, the honey could hinder the growth of several pathogenic microbes including P. aeruginosa , Escherichia coli , and S. aureus [ 116 ].…”

“…Manuka honey, produced from the nectar of Leptospermum scoparium (manuka bush), was discovered to elicit anti-microbial activity against multiple pathogens [ 116 ]. Specifically, the honey could hinder the growth of several pathogenic microbes including P. aeruginosa , Escherichia coli , and S. aureus [ 116 ]. Although the ferrozine-based iron chelation assay was utilized to determine that the honey mediates iron chelating activity [ 116 ] and the honey simulated an environment of limiting iron availability [ 116 ], it remains unclear whether the anti-microbial effect of the Manuka honey is due to its iron chelation ability.…”

“…Specifically, the honey could hinder the growth of several pathogenic microbes including P. aeruginosa , Escherichia coli , and S. aureus [ 116 ]. Although the ferrozine-based iron chelation assay was utilized to determine that the honey mediates iron chelating activity [ 116 ] and the honey simulated an environment of limiting iron availability [ 116 ], it remains unclear whether the anti-microbial effect of the Manuka honey is due to its iron chelation ability. Further investigation is needed to not only identify the potential iron chelating component in the honey but to also further investigate whether mimicking an environment with low iron content may potentially diminish the growth of P. aeruginosa , which could potentially be utilized as a strategy to overcome antibiotic resistance.…”

Evolution of Honey Resistance in Experimental Populations of Bacteria Depends on the Type of Honey, and Has no Major Side Effects for Antibiotic Susceptibility

“…Multiple mechanisms have been implicated, including high sugar/low water content, acidity, hydrogen peroxide and non-peroxide molecules such as methylglyoxal (White et al, 1963;Allen et al, 1991;Molan, 1992;Mavric et al, 2008), with floral source of the honey being a major determinant of its mechanism of action (Allen et al, 1991;Lu et al, 2013;Maddocks and Jenkins, 2013). At the phenotypic level, various effects of honey have been reported across different species, including changes in cell-wall integrity and cell shape (Henriques et al, 2011;Brudzynski and Sjaarda, 2014;Wasfi et al, 2016), quorum sensing (Truchado et al, 2009;Lee et al, 2011;Wang et al, 2012), iron acquisition (Kronda et al, 2013;Ankley et al, 2020) and biofilm formation (Merckoll et al, 2009;Badet and Quero, 2011;Halstead et al, 2016). Perhaps unsurprisingly given this complex picture of inhibitory mechanisms, research to date on the evolution of honey resistance in bacteria has reached no clear consensus.…”