The aim of this study was to verify the existence of synergistic antibacterial effect between four essential oils (Aniba rosaeodora, Melaleuca alternifolia, Origanum vulgare, and Pelargonium graveolens) individually combined with the antibacterial drug Gentamicin. We investigated the effectiveness in vitro of the association of essential oil/Gentamicin, against fifteen different strains of Gram positive and Gram negative bacteria. The antibacterial effects of these oils in combination with Gentamicin were evaluated by using the MHB microdilution method, while gas chromatography (GC) and GC/Mass spectrometry were used to analyze the chemical composition of the oils. A synergistic interaction was observed against all tested strains with the associations between the essential oils Aniba rosaeodora/Gentamicin and Pelargonium graveolens/Gentamicin. In particular a very strong synergistic interaction was observed against Acinetobacter baumannii ATCC 19606 (FIC index = 0.11). In contrast, the essential oils Origanum vulgare and Melaleuca alternifolia in association with Gentamicin were less effective on bacterial species growth. In vitro interaction can improve the antimicrobial effectiveness of the Gentamicin and may contribute to reduce its dose correlated to side effects.

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This study furnishes deeper insights to previous works on anidulafungin, demonstrating the potent activity against Candida strains planktonic cells and biofilms. Candida sp., associated with many biomaterial-related infections, give rise to infective pathologies typically associated with biofilm formation. We recently determined the in vitro antifungal activities of echinocandin anidulafungin in association with some antifungal drugs against some Candida strains in their planktonic states. A total of 11 Candida strains biofilms were tested in this study: six Candida albicans, three C. parapsilosis and two C. tropicalis. All yeast isolates and ATCC strains were stored at -20°C in glycerol stocks and were subcultured on antimicrobial agent-free Sabouraud dextrose agar plates. MIC endpoints were determined colorimetrically by using the indicator 2,3-bis(2-methoxy-4-nitro-5-sulphophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide (XTT) with menadione as electron-coupling agent. The activity of anidulafungin was assessed using in vitro microbiological model relevant for clinical practice. Anidulafungin showed a strong activity in vitro against both planktonic and biofilms cells, and our study confirms that high anidulafungin concentrations might establish paradoxical growth effect in C. albicans and C. tropicalis biofilms.

In this paper the authors investigated a synergistic antimycotic effect between four antifungal drugs Amphotericin B, Fluconazole, Tioconazole, and Flucytosine individually combined with Anidulafungin compound. This latter is considered a drug of choice in the treatment of fungal infections; it has good activity both in vitro and in vivo against yeasts and moulds, as Candida and Aspergillus. The goal of this study was to evaluate the in vitro interaction of Anidulafungin in the synergic combinations with previous reported drugs against 12 Candida strains according to CLSI M27-A3 protocol. A synergistic interaction was observed against the most antifungal strains; in particular an increasing of the antimycotic efficacy was obtained from the association between Anidulafungin and Amphotericin B or Fluconazole (Mixture 4:6). In contrast the association Tioconazole/Anidulafungin was less effective on fungal species growth. The antimycotics MIC reduction values were more evident against some strains as C. glabrata, C. krusei, C. tropicalis and C. parapsilosis.

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