Synergistic effects of mupirocin and an isoflavanone isolated from Erythrina variegata on growth and recovery of methicillin-resistant Staphylococcus aureus.
The phytochemical 2',4'-dihydroxy-8-gamma,gamma-dimethylallyl-2",2"-dimethylpyrano[5",6":6,7]isoflavanone (bidwillon B) was isolated from Erythrina variegata and its antibacterial properties against methicillin-resistant Staphylococcus aureus (MRSA) were investigated. Bidwillon B inhibited the growth of 12 MRSA strains at minimum inhibitory concentrations (MICs) of 3.13-6.25mg/l, while MICs of mupirocin were 0.20-3.13 mg/l. The minimum bactericidal concentration (MBC) for bidwillon B and mupirocin against MRSA were 6.25-25mg/l (MBC(90): 12.5mg/l) and 3.13-25mg/l (MBC(90): 25mg/l), respectively. When bidwillon B and mupirocin were combined, synergistic effects were observed for 11 strains of MRSA (fractional inhibitory concentration indices, 0.5-0.75). The MBCs of mupirocin in the presence of bidwillon B (3.13 mg/l) were reduced to 0.05-1.56 mg/l. Bidwillon B at MIC values strongly inhibited incorporation of radio-labelled thymidine, uridine, glucose and isoleucine into MRSA cells. Mupirocin showed lower inhibitory effects than bidwillon B on thymidine, uridine and glucose incorporation, but incorporation of isoleucine was completely blocked with this antibiotic. These results indicate that bidwillon B possesses sufficient anti-MRSA activity for inhibiting growth and recovery, and that the compound acts synergistically with mupirocin. The results also suggest that both compounds act on MRSA via different mechanisms. Bidwillon B may prove to be a potent phytotherapeutic and/or combination agent with mupirocin in the elimination of nasal and skin carriage of MRSA.
Department of Oral Pathology, Asahi University School of Dentistry, 1851-Hozumi, Mizuho, Gifu 501-0296, Japan.
Masaru
M
Sato
Hitoshi
H
Tanaka
Ryozo
R
Yamaguchi
Kuniki
K
Kato
Hideo
H
Etoh
D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D004357:Drug Synergism; D004895:Erythrina / Q000737:chemistry*; D005947:Glucose / Q000378:metabolism; D007529:Isoflavones / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D007532:Isoleucine / Q000378:metabolism; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D016712:Mupirocin / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism; D014529:Uridine / Q000378:metabolism
D000900:Anti-Bacterial Agents; D007529:Isoflavones; C496380:bidwillon B; D007532:Isoleucine; C065753:isoflavanone; D016712:Mupirocin; D005947:Glucose; D013936:Thymidine; D014529:Uridine