title: Effect of methylglyoxal on multidrug-resistant Pseudomonas aeruginosa.
abstract: Honey has a complex chemistry, and its broad-spectrum antimicrobial activity varies with floral source, climate, and harvesting conditions. Methylglyoxal was identified as the dominant antibacterial component of manuka honey. Although it has been known that methylglyoxal has antibacterial activity against gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus, there is not much information describing its activity against gram-negative bacteria. In this study, we report the effect of methylglyoxal against multidrug-resistant Pseudomonas aeruginosa (MDRP) using 53 clinically isolated strains. We also assessed the effect of deleting the five multidrug efflux systems in P. aeruginosa, as well as the efflux systems in Escherichia coli and Salmonella enterica serovar Typhimurium, on MICs of methylglyoxal. Our results indicate that methylglyoxal inhibits the growth of MDRP at concentrations of 128-512 μg/ml (1.7-7.1 mM) and is not recognized by drug efflux systems.
authors.affiliation: Laboratory of Microbiology and Infectious Diseases, Division of Special Projects, Institute of Scientific and Industrial Research, Osaka University Ibaraki, Osaka, Japan ; Graduate School of Pharmaceutical Sciences, Osaka University Suita, Japan.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Hayashi
authors.affiliation: Laboratory of Microbiology and Infectious Diseases, Division of Special Projects, Institute of Scientific and Industrial Research, Osaka University Ibaraki, Osaka, Japan.
authors.forename: Aiko
authors.initials: A
authors.lastname: Fukushima
authors.affiliation: Laboratory of Microbiology and Infectious Diseases, Division of Special Projects, Institute of Scientific and Industrial Research, Osaka University Ibaraki, Osaka, Japan.
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Hayashi-Nishino
authors.affiliation: Laboratory of Microbiology and Infectious Diseases, Division of Special Projects, Institute of Scientific and Industrial Research, Osaka University Ibaraki, Osaka, Japan.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Nishino
keywords: Pseudomonas aeruginosa; drug efflux system; manuka honey; methylglyoxal; multidrug resistance