Growth response and modeling the effects of Carum copticum essential oil, pH, inoculum level and temperature on Escherichia coli O157:H7

摘要

Enterohemorrhagic?Escherichia coli?O157:H7 (EHEC) is an important verotoxin producingE. coli?(VTEC). It is associated with food and water borne infections. This study was designed to carefully examine the effects of four different factors on the growth of?E. coliO157:H7 in the brain heart infusion broth. These factors included four concentrations ofCarum copticum?(Zenyan in Persian) essential oil (0, 0.015, 0.03 and 0.06%), with the major components of thymol (57.18%), p-cymene (22.55%), and γ-terpinene (13.07%), two incubation temperatures (35 and 25°C), three levels of pH (5, 6 and 7) and two inoculum size (103?and 105?cfu ml-1). The experiment was carried out in triplicate. Growth was monitored by?visible turbidity during a 30-day period. To evaluate the effects of explanatory variable on time to detection of bacterial growth, parametric survival model based on the weibull distribution was used. All explanatory variables had significant association with time to detection (P < 0.05). The models accurately predicted the growth initiation and inhibition of?E. coli?O157: H7.