Chemical composition of Lippia spp. essential oil and antimicrobial activity against Aeromonas hydrophila

Phytotherapy can replace antibiotic administration as an alternative to control Aeromonas hydrophila, one of the main bacteria involved in the aetiology of farmed fish diseases. Given that plants of the Lippia spp. genus show biological potential for antimicrobial activity, this study evaluated the chemical composition of essential oils extracted from Lippia alba, Lippia origanoides and Lippia sidoides and their activity against A.hydrophila. The oils were obtained by steam distillation in a Clevenger-type apparatus and their composition determined by gas chromatography and mass spectrometry (CG/MS). Antibacterial activity was assessed by calculating the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using broth microdilution method. The main compounds identified were geranial (25.4%) and neral (16.6%) in L.alba oil, carvacrol (40.4%) and p-cymene (11.4%) in L.origanoides oil and thymol (76.6%) and ortho-cymene (6.3%) in L.sidoides oil. The three Lippia species showed bacteriostatic and bactericidal action against A.hydrophila, with MICs and MBCs ranging from 1250 to 5000gmL(-1). Of the species tested, the best performance was obtained with essential oil of L.sidoides.