Resumo

Methicillin resistant S. aureus (MRSA) are MDR strains that cause potentially fatal systemic diseases and skin infections. They have been isolated with high frequency from hospital environment, however has been verified an increasing in the prevalence of infections caused by community-acquired MRSA. The ability to potentiate the antibiotic activity by natural products, like plants, has been investigated with the aim of to increase the effectiveness of such drugs against multidrug-resistant microorganisms. The specie Mimosa caesalpiniaefolia Benth., known as sabiá, is a plant of the family Leguminosae, which occurs naturally in several areas of the Caatinga of Brazilian Northeastern. The use of M. caesalpiniaefolia Benth. as medicinal plant is currently done in a home and the bark is used in the form of infusion to produce a kind of tonic for the treatment of bronchitis and baking the shells that are used to stop bleeding and for cleaning wounds. The dichloromethane fraction of M. caesalpiniaefolia fruits (MCFR-DCM) was tested for their antimicrobial activity alone or in combination with conventional antibiotics used in the treatment of infectious diseases caused by Staphylococcus aureus. The natural product didn’t show antimicrobial activity against multi-drug resistant strain at the clinically significant concentrations tested, once the minimal inhibitory concentration (MIC) was >1024 µg/mL. On the other hand, a synergistic effect was verified when MCFR-DCM was used in association with Neomycin and Amikacin for MRSA. The MIC values for Neomycin and Amikacin alone were 992.1 and 312.5 µg/mL, respectively. These were reduced to 312.5 and 98.4 µg/mL, respectively, when they were associated with the MCFR-DCM against MRSA. A similar synergism was observed when the natural products were changed for chlorpromazine, a drug able to inhibit efflux pumps, suggesting the involvement of resistance mediated by efflux system. Therefore, suggest that natural products from M. caesalpiniaefolia Benth. could be used as a source of compounds with Aminoglycoside-modifying activity, resulting in a new approach against bacterial resistance to antibiotics.