The MICs and MBCs of obtained essential oils determined by
micro-well dilution assay were shown as Table 3. All three essential
oils showed broad-spectrum antibacterial activities against
four foodborne pathogenic bacteria. And the negative control
(2% DMSO) had no antibacterial effect on any microorganism
tested. The sensitivities to each kind of essential oil were bacteria
type-dependent. The MICs of three essential oils were in a range of 1.25–10 mg/mL, and MBCs of them ranged from 5 to
more than 10 mg/mL, respectively. In this assay, the strongest
activities were tested on fruits oil against selected bacteria, with
MICs of 1.25 mg/mL (S. aureus, B. subtilis and E. coli) to 2.5 mg/mL
(P. aeruginosa) and MBCs of 2.5 mg/mL (S. aureus, B. subtilis and
E. coli) and 5 mg/mL (P. aeruginosa). And the highest MIC values
(10 mg/mL) and MBC values (>10 mg/mL) were found in leaves
essential oil towards tested bacteria. However, the leaves essential
oils had strong inhibitory effect on E. coli at the MIC of 2.5 mg/mL
and MBC of 5 mg/mL. The stems essential oil had the moderate bactericidal
activities against four tested bacteria with the MIC values
of 2.5–5 mg/mL, and MBC of 5 mg/mL. From the values of MICs and
MBCs, the antibacterial activities of fruits oil were the strongest,
while the leaves essential oil had the weakest antibacterial activities.
In addition, P. aeruginosa was found to be the most resistant
bacteria to the three essential oils, which was consistent with the
results of previous studies (Gilles et al., 2010; Sarrazin et al., 2012).