Clove oil reduces the aminoglycoside resistance of Pseudomonas aeruginosa

The worldwide emergence of multi-drug resistance (MDR) in clinical Pseudomonas aeruginosa strains necessitates the development of novel therapeutic strategies and fuels the investigation of alternative treatment options.

Given that natural substances in essential oils and extracts from plants are ethnopharmaceutically well documented and have long been known to exert antimicrobial activity in traditional medicine [1], we here surveyed the synergistic antimicrobial effects of clove oil (Syzygium aromaticum (L.) MEER. & L.M. PERRY) with the aminoglucoside antibiotic gentamicin against distinct clinical MDR P. aeruginosa isolates.

The results from determinations of the minimal inhibitory concentrations (MIC) in geometric dilution series and subsequent checkerboard used for calculations of the fractionated inhibitory concentration index (FICI) revealed that clove oil significantly lowered the gentamicin MIC from 8192 mg/l to ≤256. The significance of synergy was confirmed by FIC index values of ≤ 0.0625. Notably, the concentrations of clove oil that increase the antibiotic susceptibility significantly were with 0,25 % far below the MIC of >8% and so did not inhibit the growth of MDR P. aeruginosa strains under investigation.

In future investigations further aminoglycoside antibiotic compounds will be analyzed in combination with cloveoil for potential synergistic antimicrobial effects in more clinical isolates of MDR P. aeruginosa. In addition, the molecular main components of clove oil such as eugenol and essential oils from other plants will be examined for synergy with other antibiotics.

• References

• 1 Andrade BMFT, Barbosa LN, Probst IDA, Fernandes Júnior A. Antimicrobial activity of essential oils. J Essent Oil Res 2014; 26 (01) : 34-40