Antibacterial and Antibiofilm Activity of Essential Oils Against spp. Isolated from Rainbow Trout.

spp. is a major pathogen in aquaculture with a great negative economic impact. Essential oils (EOs) are compounds of the secondary metabolism of plants known for their antibacterial and antibiofilm activities. In this study, in vitro antibacterial activity of eight EOs: tea tree (extracted from ), eucalyptus (extracted from LABILL.), knee timber (extracted from L.), peppermint (extracted from L.), oregano (extracted from L.), rosemary (extracted from L.), thyme (extracted from L.) and pine EO (extracted from L.), obtained from Calendula a.s., was evaluated. Their antibacterial activity was demonstrated against spp. isolates. Oregano and thyme EOs showed the strongest activity against all tested isolates at low concentrations, followed by tea tree and peppermint EOs. The MIC value ranged from 0.06 µL/mL to 1.0 µL/mL. The tested EOs showed a significant antibiofilm activity against biofilm-forming isolates with MBIC ranging from 0.015 µL/mL to 0.25 µL/mL. All tested isolates were obtained from rainbow trout free of clinical signs of infection. Twelve isolates of subsp. , four and four isolates of were identified. The results of the in vitro study showed a significant effect of EOs against spp., which confirmed their potential for use in aquaculture as a prevention against bacterial diseases and a way of reducing the use of antibiotics.