Atividade antimicrobiana e antibiofilme dos extratos das folhas de Cochlospermum regium (Schrank) Pilger frente à Staphylococcus aureus resistente à meticilina

Abstract

Staphylococcus aureus is an opportunistic pathogen that causes a variety of infections. The development of resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) is associated with high mortality rates, and has been a major public health concern. In the past, MRSA was considered a pathogen unique to the hospital environment, and they were described as MRSA associated with hospital care (HA-MRSA), but in the last decades this has changed with the appearance of MRSA in patients with no history of hospitalization, known as community-associated MRSA (CA-MRSA). Allied to this, S. aureus is able to adhere to several surfaces and form biofilm, making the cells more protected. The objective of this study was to evaluate the antimicrobial activity and antibiofilm activity of the aqueous and ethanolic extracts of Cochlospermum regium leaves against clinical isolates HA-MRSA and CA-MRSA and the reference strain Methicillin-sensitive S. aureus (MSSA) ATCC 25923. The antibacterial activity was evaluated by broth microdilution technique and minimal inhibitory and bactericidal concentrations were determined after treatmen t, viable cells were quantified. Enzyme inhibition was determined using the DNase and coagulase tests. The activity in biofilm formation and pre-formed biofilm was determined on polystyrene microplates and viable cells were quantified after treatment. The quantification of carbohydrates and proteins in the biofilm matrix was measured by means of a NanoDrop spectrophotometer. Both extracts showed antibacterial activity in the concentrations of 125 to 500 μg/mL against all strains evaluated, with the aqueous one being more effective. They also presented bactericidal activity against all strains tested. CA-MRSA was more sensitive to extracts than HA-MRSA. The inhibitory activity of C. regium extracts on biofilm formation and mature biofilm was also observed, and at concentration of 2,000 μg/mL, the aqueous extract inhibited 100% the biofilm formation of all the bacteria tested. Coagulase was reduced at the sub-mic concentrations of the extracts. The results indicate that extracts of C. regium can be considered as promising sources of new drugs to prevent and fight infections caused by S. aureus.