The Combined Effects of Shallot Extract by the Vacuum Rotary Evaporator Technique with Common Antibiotics against Multidrug-Resistant Bacteria

Introduction: Allium hirtifolium (Persian shallot) belongs to the Alliaceae family. Recently, the ethanolic extract of Persian shallot has significant activity against some important clinical pathogens. The present study aimed to evaluate the in-vitro antibacterial potency of the ethanolic extracts of Persian shallot (Iranian Moosir) combined with common antibiotics against five clinically important antibiotic-resistant pathogens. Methods: Antibacterial activities were determined using the disc-diffusion method. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were also evaluated using the broth microdilution method for the extract and selected antibiotics. In addition, the checkerboard technique was applied to evaluate the combined effects of the extract and antibiotics. Results: The MICs of the extract and antibiotics were within the ranges of 4-16 mg/ml and 4-128 μg/ml, respectively. The MBCs of the extract and antibiotics were within the ranges of 8-16 mg/ml and 8-128 μg/ml, respectively. The results of the checkerboard technique showed that amikacin and trimethoprim/sulfamethoxazole had synergistic effects, while levofloxacin, imipenem, and vancomycin exerted antagonistic effects on the isolates in combination with the extract. Conclusion: The in-vitro application of Persian shallot extract combined with amikacin and trimethoprim/sulfamethoxazole is recommended to effectively inhibit the growth of five clinically significant antibiotic-resistant pathogens