Inhibitory and bactericidal activities of Lippia origanoides essential oil against Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa multidrug resistant

The objective of this study was to evaluate the antimicrobial potential of essential oil (EO) from L. origanoides against Gram-negative bacteria with multidrug resistance (MDR) phenotype and to correlate the results obtained with the genetic profile of these microorganisms. The oil was extracted from the leaves of this plant by steam dragging and condensation with Clevenger equipment, the chemical components were identified and quantified by gas chromatography coupled with mass spectrometry and gas chromatography coupled with the flame ionization detector. Twenty clinical isolates and one standard strain of each species were analyzed: E. coli, K. pneumoniae and P. aeruginosa (n=63). The antibacterial potential was evaluated by broth microdilution tests. Thymol is the prevalent component (87.37%). The EO at a concentration of 312 μg/mL was effective in inhibiting 52% of E. coli strains and about 38% of K. pneumoniae. On the other hand, for P. aeruginosa a concentration of 2,500 μg/mL was needed to obtain growth inhibition of approximately 38% of the strains. Among the resistance genes detected, the highest prevalence was blaCTX-M 1/2, however, even with the presence of these genes, an antimicrobial action of this EO was observed. Therefore, the results of this study suggest that the EO of L. origanoides presented an efficient antibacterial action with potential use in the fight against infections by MDR microorganisms.