Atividade antibacteriana e antibiofilme da Lippia grata frente a isolados clínicos de Pseudomonas aeruginosa

Abstract

In the search for new possibilities of control against biofilms, studies involving the medical use of natural products have grown considerably in recent years, becoming a relevant field of research. Thus, natural antimicrobials present as an effective and economical alternative and their antimicrobial activity has already been proven in several studies carried out in countries that have a diversified flora, such as Brazil. Motivated by the search for new therapeutic strategies and considering the increasing bacterial resistance, this work had as objective to evaluate the antibacterial activity and antibiofilm of the extract and essential oil of Lippia grata against clinical isolates of Pseudomonas aeruginosa. For this purpose, 44 P. aeruginosa isolates from different clinical samples were used. The essential oil was extracted by hydrodistillation process and characterized by gas chromatography associated with mass spectrometry. The antimicrobial susceptibility profile was evaluated using the Kirby-Bauer technique and the cut off points were established according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. The antibacterial activity of the extract and essential oil was evaluated by the microdilution technique in broth, in which the MIC’s were determined using 2,3,5- triphenyltetrazolium chloride (CTT) as a bacterial metabolism developer and the MBC’s by means of growth analysis of the content of the few in Mueller-Hinton agar. The determination of biofilm formation was performed using violet crystal and based on the optical density produced by biofilms, the strains were classified as non-producing, weak producing, moderate producing and strong producing. The antibiofilm activity of the plant extract of Lippia grata was evaluated in the 25 isolates of Pseudomonas aeruginosa that had a strong or moderate Biofilm production. In the chemical characterization of L. grata essential oil, four main components were identified: carvacrol (51.4%) as major constituent, thymol (15.6%), ρ-cymene (12.2%) and γ-terpinene (4%). Among the antimicrobials tested, aztreonam showed the highest percentage of resistance (47.85), followed by imipenem and levofloxacin, both with 41.0%, meropenem (36.4%), piperacillin/tazobactam (35.0%), ceftazidime (34.1%), ciprofloxacin (31.9%) cefepime (29.6%) and gentamicin (20.5%). The L. grata extract showed antimicrobial activity in 100% of the isolates tested at 50 mg / mL (MIC90 and MBC90). The concentration of 25 mg / mL (MIC50) showed inhibitory activity in 56.8% of the isolates and bactericidal activity in 43.1% of the isolates. The essential oil of L. grata presented antimicrobial activity in 100% of the tested isolates in the concentrations between 50 mg/mL and 6,25 mg/mL (MIC90). Concentrations of 3.12 mg/mL (MIC50) and 1.56 mg/mL showed inhibitory activity in 70.4% and 27.2% of the isolates, respectively. None of the concentrations tested for essential oil presented bactericidal activity on the tested isolates. Regarding biofilm production, 18 (40.9%) isolates were classified as poor biofilm producers, 18 (40.9%) as moderate producers, 7 (15.9%) as strong producers and only 1 (2.2%) did not produce biofilm. The 25 isolates with moderate or strong biofilm production treated with the L. grata plant extract presented reduction in the formation and consolidated biofilm. It is concluded with these results that L. grata presented antimicrobial activity and antibiofilm, being configured as a promising alternative to combat pathogenic microorganisms, particularly Pseudomonas aeruginosa.