Faculty Mentor

Andrea Castillo

Document Type

Poster

Department

Biology

Abstract

Manuka honey (MH) has been documented to possess powerful anti-microbial properties through multiple mechanisms. These mechanisms include a low pH, high osmolarity, iron chelation, and its unique manuka factor (UMF), methylglyoxal (MGO). Although MGO is purported to be a major pillar in the honey’s antimicrobial properties, its activity is variable against different bacterial species. We hypothesize that MH’s other antimicrobial mechanisms may also exhibit variable activity against different bacterial species. Preliminary experiments to determine the Manuka honey minimum inhibitory concentrations (MIC) for bacterial species, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, suggested that some Manuka honey antimicrobial mechanisms change effectiveness over time, but only against some species. To investigate this further, I am conducting MIC experiments weekly with newly prepared MH and previously (“aged”) prepared MH. I initially hypothesized that the aging MH MICs will increase for bacterial species that are affected by an antimicrobial mechanism that is degraded in the aged MH. However, initial MIC experiments indicate that aging MH is more effective against S. aureus and P. aeruginosa and is no different than new MH for E. coli. In future studies, we will endeavor to compare the chemical composition of the newly prepared and aged MH and determine if the conversion of dihydroxyacetone (DHA) to MGO within diluted MH is the cause of the discrepancy between new MH and aging MH MICs against the aforementioned bacterial species. This will indicate which MH antimicrobial mechanisms are most effective against the three major pathogenic bacterial species, E. coli, P. aeruginosa, and S. aureus.

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Aging Manuka Honey Improves Antimicrobial Activity Against Pathogenic Bacteria

Manuka honey (MH) has been documented to possess powerful anti-microbial properties through multiple mechanisms. These mechanisms include a low pH, high osmolarity, iron chelation, and its unique manuka factor (UMF), methylglyoxal (MGO). Although MGO is purported to be a major pillar in the honey’s antimicrobial properties, its activity is variable against different bacterial species. We hypothesize that MH’s other antimicrobial mechanisms may also exhibit variable activity against different bacterial species. Preliminary experiments to determine the Manuka honey minimum inhibitory concentrations (MIC) for bacterial species, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, suggested that some Manuka honey antimicrobial mechanisms change effectiveness over time, but only against some species. To investigate this further, I am conducting MIC experiments weekly with newly prepared MH and previously (“aged”) prepared MH. I initially hypothesized that the aging MH MICs will increase for bacterial species that are affected by an antimicrobial mechanism that is degraded in the aged MH. However, initial MIC experiments indicate that aging MH is more effective against S. aureus and P. aeruginosa and is no different than new MH for E. coli. In future studies, we will endeavor to compare the chemical composition of the newly prepared and aged MH and determine if the conversion of dihydroxyacetone (DHA) to MGO within diluted MH is the cause of the discrepancy between new MH and aging MH MICs against the aforementioned bacterial species. This will indicate which MH antimicrobial mechanisms are most effective against the three major pathogenic bacterial species, E. coli, P. aeruginosa, and S. aureus.