Inhibition of Salmonella enteritidis and Staphylococcus aureus in nutrientbroth by mint essential oil

The effect of different concentrations (0-1.2% v/v) of mint (Mentha piperit a) essential oil on the growth/survival of Salmonella enteritidis and Staph ylococcus aureus was studied in nutrient broth, using the viable count meth od and conductance measurements. In particular the addition of mint essenti al oil reduced the total viable counts of St. aureus about 6-7 logs while t his of S. enteritidis only ca. 3 logs. The detection time measurements show ed also that the inhibitory effect of mint essential oil was affected by th e incubation temperature as well as by the concentration of essential oil a dded in the growth medium. At low concentration of essential oil (<0.1%), t he addition of glucose in the growth medium prevented the formation of stap hylococcal enterotoxin B, while the reduction of viable cells was only 2 lo gs. This glucose effect was not evident in Salmonella enteritidis samples. The percentage of glucose utilization in the growth medium of both pathogen s, was reduced drastically with the addition of essential oil and as a cons equence the assimilation or formation of different compounds, such as lacta te, formate and acetate in the growth medium was also affected. (C) 2000 El sevier Science Ltd. All rights reserved.