Effect of essential oils on the viability and morphology of Escherichia coli (SP-11).

Abstract

The four essential oils (aromatic plant products) from palmarosa (Pm), lemongrass (Lg), peppermint (Pt) and eucalyptus (Eu) plants were found to be bactericidal to Escherichia coli strain SP-11, at a concentration of 1.66 (Pm, Lg and Eu) or 2.5 (Pt) microl ml-1. This effect was observed both at 37 degrees C and 4 degrees C and was not prevented by immediate tenfold dilution or by the presence of 0.5 M sucrose. Pm and Pt but not Lg or Eu induced the formation of elongated filamentous forms, some measuring 60-70 micrometers long.