Novel inhibitory activity of the Staphylococcus aureus NorA efflux pump by a kaempferol rhamnoside isolated from Persea lingue Nees

TY - JOUR

T1 - Novel inhibitory activity of the Staphylococcus aureus NorA efflux pump by a kaempferol rhamnoside isolated from Persea lingue Nees

AU - Holler, Jes Gitz

AU - Christensen, Søren Brøgger

AU - Slotved, Hans-Christian

AU - Rasmussen, Hasse Bonde

AU - Guzman, A.

AU - Olsen, Carl Erik

AU - Petersen, Bent

AU - Mølgaard, Per

PY - 2012/5

Y1 - 2012/5

N2 - Objectives: To isolate a plant-derived compound with efflux inhibitory activity towards the NorA transporter of Staphylococcus aureus. Methods: Bioassay-guided isolation was used, with inhibition of ethidium bromide efflux via NorA as a guide. Characterization of activity was carried out using MIC determination and potentiation studies of a fluoroquinolone antibiotic in combination with the isolated compound. Everted membrane vesicles of Escherichia coli cells enriched with NorA were prepared to study efflux inhibitory activity in an isolated manner. Results: The ethanolic extract of Persea lingue was subjected to bioassay-guided fractionation and led to the isolation of the known compound kaempferol-3-O-α-l-(2,4-bis-E-p-coumaroyl)rhamnoside (compound 1). Evaluation of the dose-response relationship of compound 1 showed that ethidium bromide efflux was inhibited, with an IC 50 value of 2 μM. The positive control, reserpine, was found to have an IC 50 value of 9 μM. Compound 1 also inhibited NorA in enriched everted membrane vesicles of E. coli. Potentiation studies revealed that compound 1 at 1.56 mg/L synergistically increased the antimicrobial activity of ciprofloxacin 8-fold against a NorA overexpresser, and the synergistic activity was exerted at a fourth of the concentration necessary for reserpine. Compound 1 was not found to exert a synergistic effect on ciprofloxacin against a norA deletion mutant. The 2,3-coumaroyl isomer of compound 1 has been shown previously not to cause acute toxicity in mice at 20 mg/kg/day. Conclusions: Our results show that compound 1 acts through inhibition of the NorA efflux pump. Combination of compound 1 with subinhibitory concentrations of ciprofloxacin renders a wild-type more susceptible and a NorA overexpresser S. aureus susceptible.

AB - Objectives: To isolate a plant-derived compound with efflux inhibitory activity towards the NorA transporter of Staphylococcus aureus. Methods: Bioassay-guided isolation was used, with inhibition of ethidium bromide efflux via NorA as a guide. Characterization of activity was carried out using MIC determination and potentiation studies of a fluoroquinolone antibiotic in combination with the isolated compound. Everted membrane vesicles of Escherichia coli cells enriched with NorA were prepared to study efflux inhibitory activity in an isolated manner. Results: The ethanolic extract of Persea lingue was subjected to bioassay-guided fractionation and led to the isolation of the known compound kaempferol-3-O-α-l-(2,4-bis-E-p-coumaroyl)rhamnoside (compound 1). Evaluation of the dose-response relationship of compound 1 showed that ethidium bromide efflux was inhibited, with an IC 50 value of 2 μM. The positive control, reserpine, was found to have an IC 50 value of 9 μM. Compound 1 also inhibited NorA in enriched everted membrane vesicles of E. coli. Potentiation studies revealed that compound 1 at 1.56 mg/L synergistically increased the antimicrobial activity of ciprofloxacin 8-fold against a NorA overexpresser, and the synergistic activity was exerted at a fourth of the concentration necessary for reserpine. Compound 1 was not found to exert a synergistic effect on ciprofloxacin against a norA deletion mutant. The 2,3-coumaroyl isomer of compound 1 has been shown previously not to cause acute toxicity in mice at 20 mg/kg/day. Conclusions: Our results show that compound 1 acts through inhibition of the NorA efflux pump. Combination of compound 1 with subinhibitory concentrations of ciprofloxacin renders a wild-type more susceptible and a NorA overexpresser S. aureus susceptible.

U2 - 10.1093/jac/dks005

DO - 10.1093/jac/dks005

M3 - Journal article

C2 - 22311936

SN - 0305-7453

VL - 67

SP - 1138

EP - 1144

JO - Journal of Antimicrobial Chemotherapy

JF - Journal of Antimicrobial Chemotherapy

IS - 5

ER -