The antimicrobial activity of four commercial essential oils in combination with conventional antimicrobials.
OBJECTIVE
Due to the emergence of multi-drug resistance, alternatives to conventional antimicrobial therapy are needed. This study aims to investigate the in vitro pharmacological interactions between essential oils (considered valuable as natural therapeutic treatments) and conventional antimicrobials (ciprofloxacin/amphotericin B) when used in combination.


RESULTS
Interactions of the essential oils (Melaleuca alternifolia, Thymus vulgaris, Mentha piperita and Rosmarinus officinalis) when combined with ciprofloxacin against Staphylococcus aureus indicate mainly antagonistic profiles. When tested against Klebsiella pneumoniae the isobolograms show antagonistic, synergistic and additive interactions depending on the combined ratio. The R. officinalis/ciprofloxacin combination against K. pneumoniae displayed the most favourable synergistic pattern. The interactions of M. alternifolia (tea tree), T. vulgaris (thyme), M. piperita (peppermint) and R. officinalis (rosemary) essential oils with amphotericin B indicate mainly antagonistic profiles when tested against Candida albicans.


CONCLUSIONS
While a number of interactions show complete antagonism, others show varied (synergistic, additive and/or antagonistic) interactions, thus the efficacy is dependent on the ratio in which the two components co-exist.


CONCLUSIONS
The predominant antagonistic interactions noted here, suggests that some natural therapies containing essential oils should be used with caution when combined with antibiotics.
van Vuuren
S F
SF
Department of Pharmacy and Pharmacology, Faculty of Health Sciences, University of the Witwatersrand, Parktown, South Africa. sandy.vanvuuren@wits.ac.za
Suliman
S
S
Viljoen
A M
AM
D000666:Amphotericin B / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects; D002939:Ciprofloxacin / Q000494:pharmacology; D004336:Drug Antagonism; D004347:Drug Interactions; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D006801:Humans; D007219:Industrial Oils; D007711:Klebsiella pneumoniae / Q000187:drug effects; D031650:Melaleuca / Q000737:chemistry; D036142:Mentha piperita / Q000737:chemistry; D008826:Microbial Sensitivity Tests; D009822:Oils, Volatile / Q000494:pharmacology*; D027542:Rosmarinus / Q000737:chemistry; D013211:Staphylococcus aureus / Q000187:drug effects; D046930:Thymus Plant / Q000737:chemistry
D000900:Anti-Bacterial Agents; D009822:Oils, Volatile; D002939:Ciprofloxacin; D000666:Amphotericin B; C053775:rosemary oil