Effects of Carum Copticum essential oil on growth and gene expression of enterotoxins A and C in Staphylococcus aureus in Kilka fish (Clupeonella cultriventris caspia) surimi

The effect of essential oil (EO) from Carum copticum at concentrations of 0 (control), 0.5%, 0.75% and 1% on Staphylococcus aureus growth and gene expression of enterotoxins (SE) A and C in surimi from kilka (Clupeonella cultriventris caspia) was determined during 0, 5, 10, 15 and 20 days of refrigeration storage (4 °C). The main compounds of EO were thymol (36.4%), p-cymene (31.4%) and γ-terpinen (21.73%). Minimum inhibitory concentration and maximum tolerable concentration of EO against in S. aureus in broth medium were 0.06% and 0.015%, respectively. The growth rate significantly differ between S.aureus population in control (11.31 log CFU/g) and EO-treated samples, 9.76, 7.21 and 6.06 log CFU/g in samples containing 0.5%, 0.75% and 1%, respectively. The highest inhibitory activity against gene transcription of entertoxins was observed at 1% EO; also, the inhibitory effect of EO concentrations against expression of enterotoxin C was higher than enterotoxin A., as enterotoxin A expression was 4.5 and 8.23 fold lower than control at days 5 and 20, and enterotoxin C expression, at days 5 and 20, decreased 5.11 and 8.94 fold compared to control. The results of this study showed that EO from C. copticum is an effective component in reducing bacterial growth rate and staphylococcal enterotoxins production in kilka surimi.