Thymol and menthol as two natural bioactive compounds reduce antibiotic resistance of Pseudomonas aeruginosa

BACKGROUND AND OBJECTIVESPseudomonas aeruginosa, which is the main cause of nosocomial infections, is resistant to various antibiotics. Hence, this study investigated the efficacy of menthol and thymol, as two natural derivatives, on the antibiotic resistance of Pseudomonas aeruginosa.MATERIALS AND METHODSThe antibiotic susceptibility of the strains was evaluated using the disk diffusion method. Five standard antibiotic disks, namely Ciprofloxacin (CP۵), Levofloxacin (LEV۵), Imipenem (IPM۱۰), Ceftazidime (CAZ۳۰), and Aztreonam (AZT۳۰) were used in the test. To check the effectiveness of the antibiotics without bioactive compounds (menthol and thymol), bacterial suspensions (۱.۵ × ۱۰۸ CFU.mL-۱) were streaked out on plates containing Mueller-Hinton Agar, followed by placing the antibiotic disks on the culture media. The sub-MIC values of thymol (x̅= ۱۲.۷۹ mg.mL-۱) and menthol (x̅= ۹.۳۷ mg.mL-۱) for each bacterial strain were obtained and then the susceptibility test in the presence of the bioactive compounds was carried out following the same procedure taken in the test without the compounds. The diameter of the inhibitory zone (DIZ) was measured after the incubation and the resistance profiles were determined according to the CLSI guidelines.RESULTS AND DISCUSSIONThe antibiotics were not able to inhibit the growth of the bacterial strains in the antibiogram test without bioactive compounds. This is while most of the strains lost their resistance under the influence of the sub-MIC values of menthol and thymol. Overall, it was found that the strains showed the highest sensitivity to the antibiotics Imipenem (IPM۱۰) and Aztreonam (AZT۳۰), while all of them were resistant to Ceftazidime (CAZ۳۰) in the susceptibility test with both compounds.CONCLUSIONThe present study shows that menthol and thymol can be introduced as promising inhibitors against different strains of Pseudomonas aeruginosa

کلیدواژه ها:

Antibiogram ، Antibiotic resistance ، Bioactive compounds ، Pseudomonas aeruginosa