modeling the growth of staphylococcus aureus as affected by black zira (bunium persicum) essential oil, temperature, ph and inoculum levels

black zira (bunium persicum) is a medicinal plant and spice, naturally grows in iran. the aim of this study was to investigate the combined effects of different concentrations of bunium persicum essential oil (eo; including 0, 0.08, 0.16 and 0.24%), three incubation temperatures (15, 25 and 35˚c), three levels of ph (5, 6 and 7 adjusted by hydrochloric acid), and three inoculum size (102, 103 and 104 cfu ml-1) on the growth of staphylococcus aureus in the brain heart infusion broth. black zira eo was extracted and its component was identified using gas chromatography-mass spectrometry (gc-ms) analyses. the experiment was carried out in triplicate. growth was monitored by visible turbidity during a 30-day period. to evaluate effects of explanatory variable on time to detection (ttd) of bacterial growth, parametric survival models based on log-normal distribution was used. all explanatory variables had significant association with time to detection (p < 0.05). the final model accurately predicted the growth initiation and inhibition of s. aureus.