Given the urgent need for novel methods to control the spread of multidrug-resistant microorganisms, this study presents a green synthesis approach to produce silver nanoparticles (AgNPs) using the bark extract from Anadenanthera colubrina (Vell.) Brenan var. colubrina. The methodology included obtaining the extract and characterizing the AgNPs, which revealed antimicrobial activity against MDR bacteria. A. colubrina species is valued in indigenous and traditional medicine for its medicinal properties. Herein, it was employed to synthesize AgNPs with effective antibacterial activity (MIC = 19.53–78.12 μM) against clinical isolates from the ESKAPEE group, known for causing high hospitalization costs and mortality rates. Despite its complexity, AgNP synthesis is an affordable method with minimal environmental impacts and risks. Plant-synthesized AgNPs possess unique characteristics that affect their biological activity and cytotoxicity. In this work, A. colubrina bark extract resulted in the synthesis of nanoparticles measuring 75.62 nm in diameter, with a polydispersity index of 0.17 and an average zeta potential of −29 mV, as well as low toxicity for human erythrocytes, with a CC₅₀ value in the range of 961 μM. This synthesis underscores its innovative potential owing to its low toxicity, suggesting applicability across several areas and paving the way for future research.

Background/Objectives: Wounds from burns are susceptible to infections, allowing multidrug-resistant microorganisms to complicate treatments and patient recovery. This highlights the development of new strategies to control these microorganisms. This work evaluated the antibacterial activity of hydrogels containing biogenic silver nanoparticles (bio-AgNP) and Origanum vulgare essential oil (OEO) against multidrug-resistant bacteria. Methods: The formulations were subjected to organoleptic, pharmacotechnical, and stability characterization and antimicrobial activity assessment by time–kill tests and alternative methods, an ex vivo model using porcine skin, and an in vivo model using Galleria mellonella. Results: All hydrogels maintained their stability after the thermal stress. The hydrogel containing bio-AgNP + OEO 1% (HAgNP + OEO1) presented bactericidal effectiveness, within 2 h, against both Gram-positive and Gram-negative multidrug-resistant bacteria in the time–kill test. For alternative testing, HAgNP + OEO1 was compared with 1% silver sulfadiazine (SS) and the base formulation. In the ex vivo test, both HAgNP + OEO1 and SS treatments showed a similar reduction in superficial washing of the burn for S. aureus 999, while for P. aeruginosa, the reduction was more expressive for SS treatment. In the burn tissue, HAgNP + OEO1 treatment was more effective against S. aureus 999, while for P. aeruginosa 1461, both formulations were similarly effective. In the Galleria mellonella test, survival rates after 48 h were 84% for the control group (base) and 50% for both HAgNP + OEO1 and SS treatment groups. Conclusions: This study demonstrates that the hydrogel combining antimicrobials is effective against multidrug-resistant microorganisms, offering a promising alternative for the treatment of infected burns.

Acinetobacter baumannii is a microorganism of major global clinical importance, whose carbapenem-resistant phenotype is considered a priority target for the development of new antimicrobial agents. Carbapenem-resistant A. baumannii is associated with healthcare-associated infections and exhibits high mortality rates, prolonged hospital stays, and extensive use of intensive care units. As a control strategy, green-synthesized silver nanoparticles have gained increasing attention. Based on this, the aim of this study was to synthesize a novel triphasic silver nanocomposite, characterize it, and evaluate its antibacterial activity against extensively drug-resistant and pan-drug-resistant isolates. The nanocomposite was synthesized using cell-free bacterial supernatant and was physicochemically characterized regarding concentration, size, morphology, and crystallinity. Its antibacterial activity was assessed using broth microdilution and time–kill assays, followed by toxicity assays using human erythrocytes. A nanoscale and stable nanocomposite was obtained and was composed of metallic silver, silver chloride, and silver phosphate, which exhibited antibacterial activity against all tested isolates. In the toxicity assay, the nanocomposite demonstrated low toxicity and a high selectivity index. These findings demonstrate that Ag/AgCl/Ag₃PO₄ nanocomposite exhibits strong activity against resistant phenotypes for which therapeutic options are limited, highlighting its potential as a control strategy against this pathogen.

Background/Objectives: Resistance and toxicity limit topical agents for infected burns. We evaluated biogenic silver nanoparticles (bio-AgNPs) combined with Brazilian stingless bee Scaptotrigona bipunctata honey (SB honey). Methods: Bio-AgNPs and honeys from three stingless bee species and Apis mellifera were screened against 11 reference and multidrug-resistant (MDR) strains, including MRSA, MDR Escherichia coli, and MDR Pseudomonas aeruginosa. The most active, SB honey, was combined with bio-AgNPs and assessed by checkerboard (FICI), time-kill, and scanning electron microscopy (SEM). Each agent’s cytotoxicity was determined in HaCaT keratinocytes. Results: Combinations were synergistic (FICI 0.50) against the three Gram-negative strains tested and additive (FICI 0.75) against the three Gram-positive ones, lowering both inhibitory concentrations up to fourfold. The combination reduced viable counts below detection faster than either agent alone at its MBC against MDR P. aeruginosa (30 vs. 60 min) and S. aureus (7 vs. 10–24 h), and matched the fastest single agent against E. coli, at two- to fourfold lower concentrations of both. SEM showed surface damage and incomplete septa. These reduced concentrations fell below each agent’s CC₅₀, increasing the calculated selectivity index. Conclusions: Bio-AgNPs and SB honey act jointly against the reference and MDR strains tested, all associated with burn infections, at concentrations below each agent’s cytotoxic threshold, supporting their further development as a topical antimicrobial.