Modeling the growth of Staphylococcus aureus as affected by black zira (Bunium persicum) essential oil, temperature, pH and inoculum levels

Abstract

Black zira (<em>Bunium persicum</em>) 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 <em>Bunium persicum</em> 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, 10³and 10⁴CFU mL^-1) on the growth of <em>Staphylococcus aureus</em> 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 (<em>p </em>< 0.05). The final model accurately predicted the growth initiation and inhibition of <em>S. aureus.</em>