Enhancement of the antibiotic activity against a multiresistant Escherichia coli by Mentha arvensis L. and chlorpromazine.

BACKGROUND

This is the first report testing the antibiotic resistance-modifying activity of Mentha arvensis.

METHODS

In this study an ethanol extract of M. arvensis L. and chlorpromazine were tested for their antimicrobial activity alone or in combination with conventional antibiotics against strains of Escherichia coli.

RESULTS

The growth of two E. coli strains tested was not inhibited by the extract. The minimum inhibitory concentration and minimal bactericide concentration values were >or=1 mg/ml for both strains of E. coli used. A potentiating effect of this extract on gentamicin was demonstrated. Similarly, there was a potentiating effect of chlorpromazine on kanamycin, amikacin and tobramycin, indicating the involvement of an efflux system in the resistance to these aminoglycosides.

CONCLUSIONS

It is therefore suggested that extracts from M. arvensis could be used as a source of plant-derived natural products with resistance-modifying activity, such as in the case of gentamicin, constituting a new weapon against bacterial resistance to antibiotics, as with chlorpromazine.