Determination of antimicrobial activities of some essential oils on fish pathogen bacteria

The antimicrobial activity of medicinal and aromatic plants is of great importance in terms of alternative medicine. The scents and aromas of these plants have been used in the treatment of diseases for many years. In this thesis, the antibacterial activity of herbal essential oils with a high potential to be evaluated as a new treatment strategy against bacterial diseases, which is one of the leading infectious agents, is emphasized. For this purpose, gram negative (P. aeruginosa and K. pneumoniae) and gram positive (Enterococcus faecalis and Staphylococcus) essential oils obtained from thyme (Thymbra spicata L.), black head (Lavandula stoechas L.) and laurel (Lauris nobilis L.) plants. aureus) bacteria were investigated by disc diffusion and microdilution broth methods. In this study, laurel essential oil showed a narrow spectrum of action with an inhibition zone diameter of 10.3±0.3 mm on P. aureginosa, E. faecalis, and 8.6±0.3 mm on S. aureus, except for K. pneumoniae. Zone diameters of zahter essential oil on S. aureus, P. aureginosa and E. faecalis, K. pneumoniae were 12.3 mm, respectively; 10.3mm; It was determined as 10.3 mm and 8.6 mm. It has been determined that black head essential oil has an antibacterial effect with its inhibition zone diameter that stops the growth of bacteria other than K. pneumoniae, and the zone diameter ranges are examined as 10.3-8.6 mm inhibition zone diameter-1. When compared to the standard antibiotic, laurel essential oil showed a narrow spectrum of inhibitory effect similar to ampicillinsulbactam on P. aureginosa, but low (p<0.01) or ineffective (p>0.05) on E. faecalis and S. aureus. Zahter and blackhead essential oils showed the same effect on P. aureginosa; in others, a lower effect was studied. The results of the microdilution broth method showed that laurel essential oil was grown at a concentration of 100 µL on P. aureginosa, and 50 µL on E. faecalis and S. aureus, but it was not effective. MIC values of zahter essential oil were 50 µL for K. pneumoniae, E. faecalis except P. aureginosa (growth not inhibited); It was traced to 25 µL for S. aureus. It was determined that black head plant inhibited the growth of microorganisms except K. pneumoniae at 25-50 µL. In our study, laurel and blackhead essential oils did not show an antimicrobial effect for K. pneumoniae; showed a bacteriostatic effect on others (P. aureginosae, E. faecalis and S. aureus). Zahter essential oil has an inhibitory effect on P. aureginosa and E. faecalis, K. pneumoniae, and a bactericidal effect on S. aureus. Our study findings show that although plant essential oils have inhibitory concentrations to stop the growth of pathogenic bacteria, they have a profile feature that can create an effective treatment method on diseases, but it needs to be supported by more comprehensive studies on the subject.