Essential oils from oregano (Origanum vulgare), thyme (Thymus vulgaris) and cinnamom (Cinnamomum zeylanicum) were tested for their inhibitory activity against sixty Salmonella sp. isolates. These microorganisms were distributed in 20 serovars, all of them isolated from broiler chickens. Based on microdilution technique, the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were determined. The strongest antibacterial activity was obtained for oregano (MIC mean = 529mug ml-1 and MBCmean = 661mug ml-1), followed by a moderate activity for thyme (MICmean=961mug ml-1 and MBCmean=1074mug ml-1) and the lowest obtained activity observed for cinnamon (MICmean= 1335mug ml-1 and MBCmean= 1979mug ml-1). Despite of this activity pattern, the serovars of Salmonella enterica showed significant susceptibility variations. However none of them could be classified as sensitive or resistant to the three essential oils tested. At the moment, when the antibiotics, as growth promoters, are being replaced, the essential oils from spices could be a very reasonable choice and the present results show us two points: the essential oils from oregano and thyme are effective against Salmonella isolates but the variations among the serovars must be considered.
Salmonella; essential oils; oregano; thyme; cinnamon; antimicrobial activity
