Selected antimicrobial essential oils to eradicate multi-drug resistant bacterial biofilms involved in human nosocomial infections.

Biofilms are the primary source of contamination linked to nosocomial infections by promoting bacterial resistance to antimicrobial agents, including disinfectants. Using essential oils, this study aims to inhibit and eradicate the biofilm of enterobacteria and staphylococci responsible for nosocomial infections at Guelma Hospital, northeastern Algeria. Thymbra capitata, Thymus pallescens and Artemesia herba-alba essential oils were evaluated against clinical strains of Klebsiella pneumoniae, Escherichia coli, and Staphylococcus aureus. The antimicrobial activity of the essential oils under consideration was assessed using an agar disc diffusion assay and the determination of minimum inhibitory concentrations (MICs). In addition, the crystal violet method and scanning electron microscopy (SEM) evaluated biofilm inhibition and eradication by those antimicrobial agents. The results indicate that T. pallescens essential oil was the most effective antimicrobial agent against pathogenic bacteria, with large zones of inhibition (up to 50 mm against S. aureus), low MICs (0.16 to 0.63 mg/mL), and powerful biofilm eradication up to 0.16 mg/mL in both 24 h and 60-min exposure times. Thus, Algerian thyme and oregano could be used in various ways to combat the biofilm that causes nosocomial infection in local hospitals.

Efficacy of endemic Algerian essential oils against single and mixed biofilms of Candida albicans and Candida glabrata.

OBJECTIVES: This study investigated the in vitro effect of Origanum glandulosum, Ammoides verticillata, and Saccocalyx satureioides essential oils against planktonic cells and biofilms formed by single and mixed species of Candida albicans and Candida glabrata oral isolates. The effect of the essential oils in combination with amphotericin B on planktonic cells was also studied. DESIGN: The antifungal susceptibility of planktonic cells was evaluated by disc diffusion and broth microdilution methods. Resazurin assay and scanning electron microscopy (SEM) were employed to determine the antibiofilm activity. The combinatory effect was evaluated by the checkerboard method. Essential oils were characterized by gas chromatography-mass spectrometry (GC-MS). RESULTS: The minimal inhibitory concentrations (MICs) and the minimum fungicidal concentrations (MFCs) of the studied essential oils were ranged between 250 and 2000 µg/mL. Biofilms were inhibited and eradicated by the essential oils at sub-inhibitory concentrations of 500 and 1000 µg/mL, respectively. SEM studies revealed a reduction in the preformed biofilm as a result of Origanum glandulosum essential oil treatment for single and mixed biofilms. Synergistic activity was found when Origanum glandulosum essential oil was combined with amphotericin B against Candida albicans. GC-MS analysis revealed that thymol was the major compound in Origanum glandulosum (38.36 %) and Ammoides verticillata (48.99 %) essential oils, while Saccocalyx satureioides essential oil was dominated by borneol (27.36 %). CONCLUSIONS: The studied essential oils showed significant antifungal and antibiofilm activities, which support their effectiveness as promising candidates for the management of oral Candida infections.