Acinetobacter baumannii is a rapidly emerging, highly resistant clinical pathogen with increasing prevalence. In recent years, the limited number of
antimicrobial agents available for treatment of
infections with multi-
drug resistant (MDR) strains reinforced tendency for discovery of novel
antimicrobial agents or treatment strategies. The aim of the study was to determine antimicrobial effectiveness of three Myrtus communis L.
essential oils, both alone and in combination with conventional
antibiotics, against MDR A. baumannii
wound isolates. The results obtained highlighted the occurrence of good antibacterial effect of myrtle
oils when administered alone. Using checkerboard method, the combinations of subinhibitory concentrations of myrtle
essential oils and conventional
antibiotics, i.e. polymixin B and ciprofloxacine were examined. The results proved synergism among M. communis L.
essential oils and both
antibiotics against MDR A. baumannii
wound isolates, with a FIC index under or equal 0.50. Combination of subinhibitory concentrations of
essential oils and
ciprofloxacin most frequently reduced bacterial growth in synergistic manner. The similar has been shown for combination with
polymyxin B; furthermore, the myrtle
essential oil resulted in re-sensitization of the MDR
wound isolates, i.e. MICs used in combination were below the cut off for the sensitivity to the
antibiotic. Time-kill curve method confirmed efficacy of myrtle
essential oil and
polymyxin B combination, with complete reduction of bacterial count after 6h. The detected synergy offers an opportunity for future development of treatment strategies for potentially lethal
wound infections caused by MDR A. baumannii.