An Evaluation of the Antibacterial and Cytotoxic Activities of Essential Oils and Their Emulsions Against Nosocomial Pathogens

Abstract

Bacteria are the primary microorganisms responsible for nosocomial infections. This study investigates the antibacterial, biofilm-disrupting, and cytotoxic properties of essential oils and their emulsions for the treatment of nosocomial pathogens. The antibacterial activity of selected essential oils and their emulsions was evaluated against clinically relevant strains, including Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Pseudomonas aeruginosa, and Salmonella Enteritidis. Among the tested compounds, cinnamaldehyde exhibited the most potent antibacterial activity, with minimum inhibitory concentrations ranging from 1.31 to 2.62 mg/mL against both Gram-positive and Gram-negative bacteria. Other essential oils, such as cinnamon, eucalyptus, and pine, also demonstrated antibacterial effects, although their efficacy against Pseudomonas aeruginosa was comparatively limited. In biofilm assays, cinnamaldehyde effectively disrupted biofilms formed by S. aureus, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa, indicating its potential for treating biofilm-associated infections. Cytotoxicity testing revealed that while cinnamon essential oil and cinnamaldehyde exhibited cytotoxic effects at concentrations above 0.1%, other essential oils such as basil and eucalyptus were non-toxic at the tested concentrations. These findings suggest that cinnamaldehyde is a promising agent for managing nosocomial infections, combining effective antibacterial and biofilm-disrupting properties with acceptable safety for non-target cells at appropriate doses.