Antibacterial activities of plant-derived compounds and essential oils against Cronobacter strains

Essential oils (EOs) are liquid preparations produced from plant materials. Their use as inhibitors of the growth of spoilage and pathogenic microorganisms is a good alternative to the chemical additives in foods. The disc-diffusion method was used to screen the EOs from thyme, cinnamon, clove, peppermint, marjoram, cumin, rosemary, fennel, basil, lime, bergamot orange, orange, lemon, grapefruit, mandarin, cardamom, anise, and ginger, against 21 strains of Cronobacter species, including: C. sakazakii, C. muytjensii, C. turicensis, C. condimenti, and C. malonaticus. In addition, the minimum inhibitory concentration (MIC) and the maximum tolerable concentration (MTC) of thymol, trans-cinnamaldehyde, eugenol, and menthol were determined for five strains of Cronobacter spp. The most effective EOs were: thyme>cinnamon>marjoram. In turn, EOs from clove, cumin, and fennel had a moderate inhibiting effect against only some of the analyzed strains. The majority of the tested EOs: peppermint, rosemary, basil, cardamom, anise, ginger, and all EOs from citrus fruits were ineffective against all the studied strains.