Antibacterial Activity of Lippia alba (Mill) NEBr, Mentha x piperita L. and Ocimum gratissimum L. Essential Oils Against Multiresistant Salmonella enterica Serovars

This study evaluated the sensitivity of 20 Salmonella enterica serovars, isolated from poultry, bovine meat and bone meal, to commercial antibiotics and essential oils of Lippia alba (Mill) NEBr, Mentha x piperita L. and Ocimum gratissimum L. as alternative antimicrobials. The assays were conducted using disk diffusion and the microdilution technique. The disk diffusion method tested pathogen susceptibility to seven commercial antimicrobial agents and showed that all the strains were resistant to at least two antibacterial agents. The isolates were frequently resistant to streptomycin (95%), nalidixic acid (75%) and gentamicin (70%) and sensitive to norfloxacin (45%), ciprofloxacin (20%) and chloramphenicol (20%). The microdilution technique assessed the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the essential oils. The action of O. gratissimum and L. alba essential oils showed a small variation, with MIC ranging from 2,5 to 10 mg mL-1 and MBC from 5 to 10 mg mL-1. For M. piperita essential oil, MIC ranged from 16 to 40 mg mL-1and MBC from 40 to 320 mg mL-1. Therefore, essential oils of O. gratissimum and L. alba showed the highest activity against S. enterica serovars isolated from different sources, revealing their potential as natural antimicrobial agents.