Antimicrobial activity of the essential oils and isolated compounds on the hospital-borne and foodborne pathogens

Abstract

Essential oils of plants have demonstrated antimicrobial activity against various microorganisms, as an alternative to the use of conventional antibiotics. This study aimed at testing the effectiveness of essential oils of cinnamon (Cinnamomum cassia), oregano (Origanum vulgare), clove (Syzygium aromaticum), citronella (Cymbopogon nardus), plus the major compound citral against Staphylococcus aureus ATCC 25923 and citral and carvacrol against Pseudomonas aeruginosa. Tests were performed through the microdilution method in Trypticase Soy Broth (TSB) in 96 well plates to determine the Minimum Inhibitory Concentration (MIC), and then seeded in Trypticase Soy Agar (TSA) for determining the Minimum Bactericidal Concentration (MBC). The inocula were standardized (107 CFU/mL) according to the MacFarland scale. The essential oils of cinnamon, oregano and citronella showed activity against both microorganisms at different concentrations. The essential oil of clove showed no inhibitory effects. The carvacrol inhibited the growth of P. aeruginosa at the concentration of 1.25 %. Citral inhibited S. aureus from 0.03 % concentration; however, it did not exhibited activity against P. aeruginosa. The essential oil of citronella and the citral compound were the most effective against S. aureus, while the essential oil of cinnamon showed antimicrobial activity at the lowest concentrations against P. aeruginosa.