Antibacterial activity of essential oils against Stenotrophomonas maltophilia and the effect of citral on cell membrane

Stenotrophomonas maltophilia has both the pathogenic potential and the ability to cause food spoilage, and is characterized by multi-resistance to many antibiotics. Essential oils (EOs) have been reported as good antimicrobial agents. In this study, seven EOs were selected to evaluate the antibacterial effect against foodborne spoilage S. maltophilia 4-1 by disk diffusion method, broth dilution method, and fumigation treatment. The chemical compositions of EOs were analyzed via gas chromatography-mass spectrometry injecting with both gas and liquid, hoping to reveal the relationship between active compounds and antibacterial activity. The results indicated that litsea cubeba oil (LCO) exhibited a strong inhibitory effect with minimum bactericidal concentration (MBC) value of 0.125% (v/v), and only LCO showed bacteriostatic effect in fumigation treatment within the tested range. Its key active component, citral, was responsible for the antibacterial property by causing damage and rupture of cell membrane determined using fluorescent dyes and field emission scanning electron microscope. The minimum inhibitory concentration and MBC of citral against S. maltophilia 4-1 was determined to be 0.25% (v/v) and 0.5% (v/v), respectively. This study reveals the high efficiency of EOs to inhibit bacteria in terms of key active component, and provides an alternative to reduce the resistant bacteria.