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Phytochemicals increase the antibacterial activity of antibiotics by acting on a drug efflux pump.

Ohene-Agyei T, Mowla R, Rahman T, Venter H - Microbiologyopen (2014)

Bottom Line: In silico screening was used to predict the bioactivity of plant compounds and to compare that with the known EPI, phe-arg-β-naphthylamide (PAβN).Subsequently, promising products have been tested for their ability to inhibit efflux.We demonstrated the feasibility of in silico screening to identify compounds that potentiate the action of antibiotics against drug-resistant strains and which might be potentially useful lead compounds for an EPI discovery program.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, United Kingdom.

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The phytochemicals do not permeabilize the outer membrane. The permeabilizing activity of compounds was measured as an increase in initial rates of nitrocefin hydrolysis by Escherichia coli wild-type cells treated with 10 μmol/L CCCP. Dots represent no treatment and squares represent treatment with compounds at (A) PAβN at 128 μg/mL, (B) plumbagin at 100 μg/mL, (C) NDGA at 100 μg/mL, (D) quercetin at 100 μg/mL, (E) mangiferin at 500 μg/mL, and (F) shikonin at 250 μg/mL. Nitrocefin hydrolysis was monitored over time by monitoring the increase in absorbance at 490 nm. Representative fluorescent traces are shown for experiments with different cells batches done on three different days.
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fig04: The phytochemicals do not permeabilize the outer membrane. The permeabilizing activity of compounds was measured as an increase in initial rates of nitrocefin hydrolysis by Escherichia coli wild-type cells treated with 10 μmol/L CCCP. Dots represent no treatment and squares represent treatment with compounds at (A) PAβN at 128 μg/mL, (B) plumbagin at 100 μg/mL, (C) NDGA at 100 μg/mL, (D) quercetin at 100 μg/mL, (E) mangiferin at 500 μg/mL, and (F) shikonin at 250 μg/mL. Nitrocefin hydrolysis was monitored over time by monitoring the increase in absorbance at 490 nm. Representative fluorescent traces are shown for experiments with different cells batches done on three different days.

Mentions: The outer membrane permeabilizing effect of the natural products was assessed by examining the rate of hydrolysis of a chromogenic β-lactam, nitrocefin by intact cells of E. coli. Hydrolysis of nitrocefin by the β-lactamase releases a colored compound that can be measured at 490 nm. The rate of nitrocefin hydrolysis is limited by the rate of diffusion across the outer membrane, hence an increased rate of hydrolysis of nitrocefin would be indicative of outer membrane permeabilization (Lomovskaya et al. 2001). The effect of the natural products on the rate of nitrocefin hydrolysis was determined at concentrations, where they did not interfere with the A490 measurements. We observed no increase in the rate of nitrocefin hydrolysis in the presence of the natural products. We could therefore conclude that the synergism with known antibiotics observed was not due to secondary mechanisms such as membrane permeabilization (Fig. 4).


Phytochemicals increase the antibacterial activity of antibiotics by acting on a drug efflux pump.

Ohene-Agyei T, Mowla R, Rahman T, Venter H - Microbiologyopen (2014)

The phytochemicals do not permeabilize the outer membrane. The permeabilizing activity of compounds was measured as an increase in initial rates of nitrocefin hydrolysis by Escherichia coli wild-type cells treated with 10 μmol/L CCCP. Dots represent no treatment and squares represent treatment with compounds at (A) PAβN at 128 μg/mL, (B) plumbagin at 100 μg/mL, (C) NDGA at 100 μg/mL, (D) quercetin at 100 μg/mL, (E) mangiferin at 500 μg/mL, and (F) shikonin at 250 μg/mL. Nitrocefin hydrolysis was monitored over time by monitoring the increase in absorbance at 490 nm. Representative fluorescent traces are shown for experiments with different cells batches done on three different days.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263512&req=5

fig04: The phytochemicals do not permeabilize the outer membrane. The permeabilizing activity of compounds was measured as an increase in initial rates of nitrocefin hydrolysis by Escherichia coli wild-type cells treated with 10 μmol/L CCCP. Dots represent no treatment and squares represent treatment with compounds at (A) PAβN at 128 μg/mL, (B) plumbagin at 100 μg/mL, (C) NDGA at 100 μg/mL, (D) quercetin at 100 μg/mL, (E) mangiferin at 500 μg/mL, and (F) shikonin at 250 μg/mL. Nitrocefin hydrolysis was monitored over time by monitoring the increase in absorbance at 490 nm. Representative fluorescent traces are shown for experiments with different cells batches done on three different days.
Mentions: The outer membrane permeabilizing effect of the natural products was assessed by examining the rate of hydrolysis of a chromogenic β-lactam, nitrocefin by intact cells of E. coli. Hydrolysis of nitrocefin by the β-lactamase releases a colored compound that can be measured at 490 nm. The rate of nitrocefin hydrolysis is limited by the rate of diffusion across the outer membrane, hence an increased rate of hydrolysis of nitrocefin would be indicative of outer membrane permeabilization (Lomovskaya et al. 2001). The effect of the natural products on the rate of nitrocefin hydrolysis was determined at concentrations, where they did not interfere with the A490 measurements. We observed no increase in the rate of nitrocefin hydrolysis in the presence of the natural products. We could therefore conclude that the synergism with known antibiotics observed was not due to secondary mechanisms such as membrane permeabilization (Fig. 4).

Bottom Line: In silico screening was used to predict the bioactivity of plant compounds and to compare that with the known EPI, phe-arg-β-naphthylamide (PAβN).Subsequently, promising products have been tested for their ability to inhibit efflux.We demonstrated the feasibility of in silico screening to identify compounds that potentiate the action of antibiotics against drug-resistant strains and which might be potentially useful lead compounds for an EPI discovery program.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, United Kingdom.

Show MeSH
Related in: MedlinePlus