Oregano exerted its bactericidal activity at 0.125% (vol/vol) on
both strains of Staphylococcus and Listeria, after 48 h producing a
significant reduction (P < 0.05) in microbial counts that was greater
than 4 and 7 log respectively. The same concentration of Oregano
had different effects on the two Gram-negative bacteria: it showed
its bactericidal activity on Salmonella ATCC and on Campylobacter
HSD, but had bacteriostatic action on Salmonella HSD and
Campylobacter ATCC.
T. vulgaris EO at 0.125% (vol/vol) showed bactericidal activity on
both the Gram-negative after 24 h of incubation, while the percentage
able to kill the Gram-positive was higher, than the Gramnegative
one, at 0.25% (vol/vol). T. vulgaris showed a strong antimicrobial
activity against the four pathogenic bacteria with a MIC
0.5% (vol/vol). Different MIC obtained by other authors (Burt,
2004; Oussalah, Caillet, Saucier, & Lacroix, 2007) are probably
due to different characteristics of the EOs used, thanks to the large
variability of the chemical composition of each essential oil
chemotype.