Influence of carvacrol and 1,8-cineole on cell viability, membrane integrity, and morphology of Aeromonas hydrophila cultivated in a vegetable-based broth.

This study investigated the effects of carvacrol (CAR) and 1,8-cineole (CIN) alone (at the MIC) or in combination at subinhibitory amounts (both at 1/8 MIC) on the cell viability, membrane permeability, and morphology of Aeromonas hydrophila INCQS 7966 (A. hydrophila) cultivated in a vegetable-based broth. CAR and CIN alone or in combination severely affected the viability of the bacteria and caused dramatic changes in the cell membrane permeability, leading to cell death, as observed by confocal laser microscopy. Scanning and transmission electron microscopy images of bacterial cells exposed to CAR or CIN or the mixture of both compounds revealed severe changes in cell wall structure, rupture of the plasma membrane, shrinking of cells, condensation of cytoplasmic content, leakage of intracellular material, and cell collapse. These findings suggest that CAR and CIN alone or in combination at subinhibitory amounts could be applied to inhibit the growth of A. hydrophila in foods, particularly as sanitizing agents in vegetables.

The cytotoxic effect of essential oils from Origanum vulgare L. and/or Rosmarinus officinalis L. on Aeromonas hydrophila.

This study aimed to evaluate the antibacterial activities of the essential oils from Origanum vulgare L. (OV) and Rosmarinus officinalis L. (RO), both singly and in combination at sub-inhibitory concentrations (» MIC + » MIC), against Aeromonas hydrophila and to investigate the possible mechanisms underlying these activities. Used singly (OV: 2.5 µL/mL; RO: 20 µL/mL) or in a mixture (OV: 0.625 µL/mL + RO: 5 µL/L), these essential oils led to a significant decrease (p<0.01) in bacterial viability after 24 h of exposure. A decrease in glucose consumption by A. hydrophila and release of cellular material were observed immediately after the addition of the essential oils, both singly and as a mixture, and continued for up to 6 h. Electron microscopy of cells exposed to the essential oils revealed severe changes in the plasma membrane, cytoplasmic appearance, and cell shape during the 6-h exposure period. OV and RO essential oils combined at sub-inhibitory concentrations could be rationally applied to inhibit the growth of A. hydrophila in food products, particularly minimally processed vegetables.