Atividade de nanopartículas de prata biogênicas sobre Staphylococcus spp. isolados de animais

Abstract

The genus Staphylococcus comprises bacteria widely distributed in humans and animals, including species capable of causing opportunistic infections and exhibiting significant resistance to antimicrobial agents. In veterinary settings, these bacteria are particularly relevant due to the close contact between domestic animals and humans, which favors cross transmission and selects for multidrug-resistant strains. In this scenario, there is a growing need to investigate therapeutic alternatives that can overcome the loss of efficacy of conventional antibiotics. Among the most promising strategies are metallic nanoparticles, especially biogenic silver nanoparticles (bioAgNPs), whose synthesis mediated by plant extracts proves to be sustainable and capable of generating stable, reactive particles with recognized antimicrobial potential. Therefore, this study aimed to identify Staphylococcus spp. isolates from animals and to evaluate the antimicrobial and antibiofilm activity of bioAgNPs synthesized from the aqueous extract of Trichilia catigua bark. Initially, microorganisms were isolated and identified by MALDI-TOF MS mass spectrometry. Subsequently, susceptibility testing to commercial antimicrobials was performed using the disk diffusion method. Following this, the antimicrobial activity of the bioAgNPs was investigated by broth microdilution. Finally, the action of the bioAgNPs on the initial formation and mature biofilm of the bacteria was evaluated. The isolates showed a broad spectrum of resistance to conventional antibiotics, with resistance to β lactams being particularly noteworthy. In the microdilution tests, it was observed that all species were inhibited by microconcentrations of bioAgNPs, with MIC₁₀₀ values ranging from 3.37 to 6.74 µg/mL. The MBC₁₀₀ values were equal to or up to twice the MIC values, demonstrating the bactericidal nature of the nanoparticles. BioAgNPs significantly reduced the biomass of initial and mature biofilms, although without promoting complete eradication. Thus, the results demonstrate that bioAgNPs synthesized from T. catigua represent a promising and efficient approach for controlling multidrug-resistant Staphylococcus spp., including emerging species of veterinary relevance and zoonotic potential.