Electrochemical study on the natural and chemical preservatives antibacterial effect against S. aureus PTCC 1112 and its determination at low levels

Pathogen microorganisms detection, such as Staphylococcus aureus ( S. aureus ), is so critical because it can be dangerous for public health. In this research, we have tried to introduce a simple and sensitive modified biosensor by multiwalled carbon nanotubes (MWCNTs) for S. aureus PTCC 1112 detection which was inoculated in PBS (pH 7.4). The pulsed amperometric detection (PAD) method showed that by increasing the concentration of S. aureus suspension, the related current will increase linearly in a dynamic range of 1.88 × 10 7 –3.00 × 10 8 cfu mL −1 , with a detection limit of 4.85 × 10 5 cfu mL −1 . The antibacterial effect of three herbal essential oils, tea, bergamot and lemon, and three common chemical cosmetic preservatives, euxyl (phenoxyethanol:ethylhexylglycerin), benzyl alcohol and benzalib (alkyl benzyl dimethyl ammonium chloride), was compared by electrochemical and biological methods. The results based on disk diffusion agar method and PAD revealed that this biosensor can be used for comparing the effectiveness of natural and chemical preservatives to inhibit the growth of bacteria. By adding the essential oils into the S. aureus suspension in PBS, the related currents were largely decreased about 65.83% (green tea), 80.49% (bergamot) and 93.30% (lemon) that are in agreement with the inhibition zones of microbial test and comparable to chemical preservatives of euxyl (73.52%), benzyl alcohol (90.65%) and benzalib (93.81%). It demonstrates the comparative antibacterial effect of these essential oils versus chemical preservatives and the ability of MWCNTs/GCE to detect the presence or absence of S. aureus in a few minutes.