Burkholderia spp. are opportunistic human pathogenic bacteria that, in immunocompromised patients and individuals with cystic fibrosis, often cause serious respiratory infections difficult to treat due to their intrinsic resistance to most clinically available antibiotics. Previous studies confirmed that in this bacterial genus, antibiotic resistance is related to the presence of efflux pumps belonging to the RND superfamily. The purpose of this study was to find new antimicrobial compounds such as Essential Oils (EOs) in order to avoid all the problems related to therapy failures caused by the use of classical antibiotics. Some authors demonstrated EOs antibacterial activity against classical pathogens, but there are very few studies on Burkholderia spp. sensibility to EOs. EOs bactericidal effect is mainly due to the compounds derived from terpenes and terpenoids that seem to affect permeability, ions and nutrients transport of the bacterial membrane. Aromatograms with 6 different EOs: Clove (Eugenia caryophyllata), Lavender (Lavandula hybrida), Oregano (Origanum vulgare), Rosemary (Rosmarinus officinalis), Tea tree oil (Melaleuca alternifolia) and Thyme (Thymus vulgaris) were performed against Burkholderia strains, both of clinical and environmental origin (respectively 36 and 15), against 8 B. cenocepacia J2315 mutants impaired in RND transporters and the B. cenocepacia J2315 Wild type. Results demonstrated that all the tested strains were sensible to oregano and more than 80% were sensible to thyme and clove EOs. Also RND mutants were inhibited by the three mentioned EOs: RND4, the double mutant RND4/RND9 and the triple mutant RND4/RND9/RND14 had larger inhibition diameters than the other strains, the last two being also sensitive to lavender EOs. These results are in agreement with several previous studies that showed that RND4 pump is the more implicated in multi-resistance in Burkholderia pathogens. On some strains we calculated the Minimal Inhibitory Concentration (MIC), through microdilution methods, for the three more effective EOs. The MIC depended both on bacterial strains and the used EO, but were of 0.25% /vol/vol) or lower.
Antimicrobial effect of 6 essential oils against strains of Burkholderia cepacia complex, an opportunistic pathogen in Cystic Fibrosis / A. Lo Nostro; G. Pesavento; G. Flamini; M. Barnabei; C. Calonico; G. Emiliani;E. Perrin; I. Maida; C. Chiellini; M. Fondi; V. Orlandini; E. Bosi; S. Mocali; A. Fabiani; A.R. Bilia; S. Biffi; L. Gori; A. Vannacci; E. Gallo; V. Maggini; F. Firenzuoli; R. Fani. - STAMPA. - (2013), pp. 66-67. (Intervento presentato al convegno XIII Congresso della Società Italiana di Fitochimica tenutosi a Gargnano nel 19-21 settembre).
Antimicrobial effect of 6 essential oils against strains of Burkholderia cepacia complex, an opportunistic pathogen in Cystic Fibrosis
LO NOSTRO, ANTONELLA;PESAVENTO, GIOVANNA;EMILIANI, GIOVANNI;PERRIN, ELENA;MAIDA, ISABEL;FONDI, MARCO;BOSI, EMANUELE;BILIA, ANNA RITA;VANNACCI, ALFREDO;FANI, RENATO
2013
Abstract
Burkholderia spp. are opportunistic human pathogenic bacteria that, in immunocompromised patients and individuals with cystic fibrosis, often cause serious respiratory infections difficult to treat due to their intrinsic resistance to most clinically available antibiotics. Previous studies confirmed that in this bacterial genus, antibiotic resistance is related to the presence of efflux pumps belonging to the RND superfamily. The purpose of this study was to find new antimicrobial compounds such as Essential Oils (EOs) in order to avoid all the problems related to therapy failures caused by the use of classical antibiotics. Some authors demonstrated EOs antibacterial activity against classical pathogens, but there are very few studies on Burkholderia spp. sensibility to EOs. EOs bactericidal effect is mainly due to the compounds derived from terpenes and terpenoids that seem to affect permeability, ions and nutrients transport of the bacterial membrane. Aromatograms with 6 different EOs: Clove (Eugenia caryophyllata), Lavender (Lavandula hybrida), Oregano (Origanum vulgare), Rosemary (Rosmarinus officinalis), Tea tree oil (Melaleuca alternifolia) and Thyme (Thymus vulgaris) were performed against Burkholderia strains, both of clinical and environmental origin (respectively 36 and 15), against 8 B. cenocepacia J2315 mutants impaired in RND transporters and the B. cenocepacia J2315 Wild type. Results demonstrated that all the tested strains were sensible to oregano and more than 80% were sensible to thyme and clove EOs. Also RND mutants were inhibited by the three mentioned EOs: RND4, the double mutant RND4/RND9 and the triple mutant RND4/RND9/RND14 had larger inhibition diameters than the other strains, the last two being also sensitive to lavender EOs. These results are in agreement with several previous studies that showed that RND4 pump is the more implicated in multi-resistance in Burkholderia pathogens. On some strains we calculated the Minimal Inhibitory Concentration (MIC), through microdilution methods, for the three more effective EOs. The MIC depended both on bacterial strains and the used EO, but were of 0.25% /vol/vol) or lower.
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