Objective The increasing emergence of antibiotic- and biocide-resistant microorganisms has reduced the effectiveness of conventional antimicrobial strategies, highlighting the need for alternative approaches, particularly in clinical and high-risk environments. This study evaluated the antimicrobial activity and mode of action of fifteen essential oils against pathogenic microorganisms in the vapor phase. Pathogens were selected based on clinical relevance, transmission potential via direct or indirect contact, and their ability to cause severe infections, particularly in immunocompromised patients. Methodology The chemical composition of essential oils was determined by gas chromatography–mass spectrometry (GC/MS). Antimicrobial activity was assessed against five bacterial strains and two Candida species using the vapor-phase diffusion method. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were applied to visualize structural alterations in microbial cells following exposure to the most active essential oils. Results Coriandrum sativum fruit essential oil exhibited strong efficacy against Staphylococcus aureus and Pseudomonas aeruginosa . Ocimum basilicum was particularly effective against Escherichia coli . Moreover O. basilicum and Coriandrum sativum EO significantly suppressed pigment production in S. aureus . The most efficient oils against Candida albicans were Syzygium aromaticum , Mentha x piperita and C. sativum . SEM analyses revealed structural deformations in C. albican s cells, including surface shrinkage, irregular contours, partial collapse, surface rupture, and pore formation. TEM images showed disrupted cell walls, increased vacuolization, and compromised intracellular integrity following exposure to essential oil vapors. Conclusion This study contributes to understanding the anticandidal potential and morphological effects of vapor-phase essential oils, highlighting their relevance beyond antibacterial activity. The application of essential oils in their vapor phase presents notable advantages, including the avoidance of direct contact and the feasibility of use in high-risk environments, such as hospitals and communal sanitation facilities, where microbial contamination is a significant concern.
MUTLU et al. (Sun,) studied this question.