| Congresso Brasileiro de Microbiologia 2023 | Resumo: 918-1 | ||||
Resumo:Staphylococcus aureus is a member of the human microbiota, but when there is an imbalance in the immune system or disruption of skin barriers, this bacterium can cause infections that affect different anatomical sites. The ability of S. aureus to form biofilms, as well as the resistance to methicillin (MRSA) contribute to its classification as a high priority for the development of new antimicrobials by the World Health Organization. In this study, the antibacterial activity of bioAgNPs, obtained from the aqueous extract of Trichilia catigua bark, on planktonic and sessile MRSA cells was evaluated. For this, the reference strain MRSA BEC 9393 and a clinical MRSA isolate were used. The antibacterial activity of bioAgNPs on planktonic cells was evaluated by the broth microdilution method to determine minimum inhibitory (MIC) and bactericidal (MBC) concentrations. MIC and MBC were determined as the lowest concentrations capable of completely inhibiting visible growth and reducing the colony forming unit count to zero, respectively. The nature of the antibacterial activity of bioAgNPs was evaluated by the CBM/MIC ratio, and the results interpreted as bactericidal when ≤4. For sessile cells, the activity of bioAgNPs was evaluated on 24-h growth biofilms, using the MTT reduction method (3-(4,5-dimethyl-2-thiazolyl) -2,5-diphenyl-2H bromide - tetrazolium), and scanning electron microscopy (SEM). The toxicity of bioAgNPs to LLC-MK2 cells was analyzed by the MTT reduction method. BioAgNP MIC and MBC values were 8.43 µg/mL and 16.87 µg/mL, respectively, for both MRSA strains, being considered bactericidal (CBM/MIC=2). For sessile cells, the MIC capable of reducing 50% of the metabolic activity of biofilms (SCIM50) were 8.43 µg/mL for the reference strain and 16.87 µg/mL for the clinical isolate. The SCIM90 was 67.5 µg/ml for both strains. SEM images show a significant reduction in the number of sessile cells within the biofilm after treatment with bioAgNP SCIM90. The cytotoxic concentration for 50% of LLC-MK2 cells was 6.33 µg/ml. In conclusion, bioAgNPs have an antibacterial effect on planktonic and sessile MRSA cells, showing potential for the development of new alternatives for the treatment of infections caused by these bacteria. However, antibacterial concentrations are toxic for LLC-MK2 cells, and further studies are needed to reduce this toxicity for mammalian cells. Palavras-chave: antibacterial activity, antibiofilm activity, MRSA, toxicity Agência de fomento:Coordenação de Aperfeiçoamento de Pessoal de Nível Superior; Financiadora de Estudos e Projetos | |||||