2.1.4. Antimicrobial Activity

All extracts were tested against Gram-negative bacteria: *Escherichia Coli* O157:H7 ATCC 25922 CECT 434*;* and Gram-positive bacteria: *Lysteria Monocytogenes* KCTC 3569 CECT 7467 and *Staphilococcus Aureus* ATCC 25923 CECT 435. The antimicrobial activity of the different extracts was measured following the diffusion disk method described by Chanwitheesuk et al. [27] with some modifications, using a bacterial cell suspension with an equilibrated concentration to a 0.5 McFarland standard or 105–106 cfu/mL. Each bacterial suspension was spread on a Mueller-Hinton agar plate. Sterile paper discs of 6 mm diameter were impregnated with 30, 60 and 90 μL of each test sample. Chloramphenicol (30 μg), a standard antibiotic was used as a positive control, while discs with the solvents used for extraction were used as negative controls, water or MeOH. The plates were incubated at 37 ◦C for 24 h. After incubation, the inhibition zones appearing around the discs were measured and recorded. The values, expressed in mm, were averages of six measurements per disc, taken at six different points in order to minimise errors.
