Avaliação da atividade antibiofilme do óleo essencial de Protium heptaphyllum

Abstract

Controlling infections caused by multidrug-resistant Acinetobacter baumannii is yet a challenge for public health, once this pathogen has intrinsic and acquired resistance mechanisms, being involved with morbidity and mortality rate increase in hospital environment. World Health Organization nominated carbapenem resistant A. baumannii as a priority group for research aiming dissemination control as well as new antibiotic development to control the infections caused by this pathogen. The objective of this study was to evaluate Protium heptaphylum (white pitch) essential oil antibiofilm activity against clinical isolates of A. baumannii multidrug-resistant. A dilution 1:100 (v/v) of 20-hour grown cultures from eight A. baumannii multidrug-resistant strains presented a concentration of 8x105 - 2,3 x106 cfu.mL-1 . Biofilm formation capability of the analyzed strains was determined in three culture means: Brain Heart Infusion (BHI), Mueller Hinton broth (MH) and Trypticase Soy Broth (TSB). Planktonic growth and biofilm formation were variable among the isolates when considering the same culture mean, suggesting that genetic variations or phenotypical plasticity can influence on multidrug-resistant A. baumannii growth. We also observed that there was a higher propensity of biofilm formation in BHI, and a lower propensity in TSB, suggesting that nutrient differences can influence on biofilm formation. The Minimum Inhibitory Concentration (MIC) of P. heptaphylum oil against A. baumannii multidrug-resistant strains was determined using microdilution in MH broth. 0,25% dilution of the oil was capable to inhibit multidrug-resistant A. baumannii planktonic cells, showing antimicrobial activity. Incapability of biofilm production in this concentration and maintenance of total planktonic growth capability and biofilm formation in concentrations lower than 0,25% (v/v) indicate the absence of P. heptaphylum oil antibiofilm activity. Thus, this oil could be useful to treat skin infections via ointment compounds or to disinfect surfaces; however, besides multidrug resistant A. baumannii, antimicrobial activity against other bacterial species needs to be analyzed, as well as the biological safety of the oil.