EOs were tested for antibacterial activity according to published
methodology (De Feo et al., 1998). Vegetative cells of each P. larvae
strain grown in MYPGP agar for 72 h of incubation at 37 C under
microaerobic conditions were suspended in physiological solution
and adjusted to 0.5 of Mac Farland scale. An aliquot of 0.10 mL of
this solution was poured into a Petri dish containing MYPGP agar.
This aliquot was spread onto the surface of the agar using a Drigalsky
spatel until the microorganisms were absorbed. Then, a 6 mm
diameter sterilized paper filter disk, previously embedded with 10
lL of the EO under analysis, was put onto the agar surface, and the
plate was incubated at 37 C during 72 h under microaerobic
conditions.