In vitro investigation of the antimicrobial activity of Dezfuli orange peel essential oil with and without common antibiotics on some pathogenic bacteria

Given the rise in the infectious diseases caused by pathogens, identification of medicinal plants and purification of their nutraceuticals can be useful in treating such diseases. In this experimental study, the antimicrobial activity of Dezfuli orange peel essential oil was examined on 3 Gram-negative strains (Escherichia coli, Pseudomonas aeruginosa and Salmonella typhi) and 5 Gram-positive strains (Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, Staphylococcus epidermidis and Listeria innocua) through agar disc diffusion, agar well diffusion, minimum inhibitory concentration (microdilution broth) and minimum bactericidal concentration. Furthermore, the interactions between the essential oil and chloramphenicol, gentamycin and tetracycline were investigated. The results of disc diffusion showed that the longest and shortest diameters of the growth inhibition zone belonged to B. cereus (21.20 mm) and L. innocua (13.20 mm) respectively. In the agar diffusion test, S. aureus and E. coli respectively had the longest (17.30 mm) and shortest (11.10 mm) diameters of the inhibition zone. The minimum inhibitory concentration was equal to 25, 400, 50, 12.5, 25, 25, 400 and 12.5 mg/ml for E. coli, P. aeruginosa, S. typhi, S. aureus, B. cereus, B. subtilis, S. epidermidis and L. innocua respectively. The minimum bactericidal concentration of the essential oil was greater than 400 mg/ ml for all the strains.