THE EFFECT OF ESSENTIAL OILS OF BASIL ON THE GROWTH OF AEROMONAS-HYDROPHILA AND PSEUDOMONAS-FLUORESCENS

Basil essential oils, including basil sweet linalool (BSL) and basil m ethyl chavicol (BMC), were screened for antimicrobial activity against a range of Gram-positive and Gram-negative bacteria, yeasts and mould s using an agar well diffusion method. Both essential oils showed anti microbial activity against most of the micro-organisms examined except Clostridium sporogenes, Flavimonas oryzihabitans, and three species o f Pseudomonas. The minimum inhibitory concentration (MIC) of BMC again st Aeromonas hydrophila and Pseudomonas fluorescens in TSYE broth (as determined using an indirect impedance method) was 0.125 and 2% (v/v), respectively; the former was not greatly affected by the increase of challenge inoculum from 10(3) to 10(6) cfu ml(-1). Results with restin g cells demonstrated that BMC was bactericidal to both Aer. hydrophila and Ps fluorescens. The growth of Aer. hydrophila in filter-sterilize d lettuce extract was completely inhibited by 0.1% (v/v) BMC whereas t hat of Ps. fluorescens was not significantly affected by 1% (v/v) BMC. In addition, the effectiveness of washing fresh lettuce with 0.1 or 1 % (v/v) BMC on survival of natural microbial flora was comparable with that effected by 125 ppm chlorine.