New alternative for the treatment of clinical isolates of multidrug-resistant Staphylococcus aureus

VÁZQUEZ NICOLÁS; FIORILLI GRACIELA; CÁCERES GUIDO PA; MORENO SILVIA

Tiquipaya, Cochabamba

Congreso; LIII Reunión Anual de la Sociedad Latinoamericana de Investigacion Pediatrica (SLAIP 2015); 2015

Sociedad Latinoamericana de Investigacion Pediatrica

New alternative for the treatment of clinical isolates of multidrug-resistant Staphylococcus aureusObjectives: A high percentage of hospital infections are caused by methicillin-resistant Staphylococcus aureus (MRSA), therefore new strategies to combat them are required. The aim of this study was to evaluate the in vitro antibiotic effectiveness of carnosic acid, the main diterpene of Rosmarinus officinalis (rosemary) leaves, against clinical isolates of multiresistant-antibiotic Staphylococcus aureus obtained from patients of a pediatric hospital.Methods: The identification of nosocomial isolates from bacteremia was performed by catalase, coagulase and deoxyribonuclease assays as well as by mass spectrometry. Antibiotic susceptibility was determined by the classical method of Kirby-Bauer and VITEK2 automated system. The antibacterial activities were tested by dilution in liquid medium in microplates.Results: Carnosic acid inhibited a 100% the growth of three clinical isolates of MRSA: GM20 resistant to beta-lactams, cephalosporins, macrolides and lincosamides; GM31 with additional resistance to aminoglycosides, fluoroquinolones and rifampicin, and GM34 which also presented resistance to linezolide at minimum inhibitory concentrations (MIC) of 12, 24 and 12 µg/ml, respectively. The phytochemical inhibited the ATCC 25923 strain, susceptible to antibiotics, at 8 μ/ml after treatment for 24 hours. Other results demonstrated a synergistic interaction of carnosic acid with gentamicin, increasing 3-6 times its susceptibility in both susceptible (MIC < 0.5 µg/ml) and resistant (MIC > 16 µg/ml) strains to this antibiotic.Conclusions: The carnosic acid is effective to inhibit multiresistant MRSA strains alone and to potentiate the gentamicin, even in originally strains resistant to this antibiotic. These results, described here for the first time, suggest that carnosic acid is a candidate with a high potential to be use in new strategies in the treatment of infections caused by MRSA and use alone or in combination with gentamicina.