Background: Corynebacterium ulcerans is an emerging zoonotic pathogen capable of cau-sing diphtheria-like infections in humans. Objectives: we report, for the first time in Brazil, the detection and phenotypic/genomic characterization of three atoxigenic ST-339 strains isolated from domestic animals, including one with a ciprofloxacin resistance profile linked to double GyrA mutations (S89L, D93G). Methods: species identification was performed by MALDI-TOF MS, followed by in vitro antimicrobial susceptibility testing, whole-genome sequencing, and bioinformatic analyses to predict virulence determinants, antimicrobial resistance genes, CRISPR–Cas systems, mobile genetic elements, and in silico structural analysis as well as phylogenetic reconstruction. Results: whole-genome sequencing confirmed species identity, revealed high genetic similarity, and identified distinct phylogenetic subclades, suggesting potential international dissemination. Genomic analyses showed conserved virulence determinants, such as incomplete pilus clusters, iron acquisition systems, and the pld gene, with the absence of the tox gene. Molecular modeling and dynamics simulations indicated that GyrA mutations disrupt critical ciprofloxacin–magnesium–water interactions, reducing binding stability. Mobile genetic elements, prophages, and CRISPR–Cas systems underscored the genomic plasticity of these isolates. Conclusions: these findings document a little-studied antimicrobial resistance mechanism in zoonotic C. ulcerans, highlighting the need for strengthened surveillance and further research on virulence and resistance, even in ato-xigenic strains.

Corynebacterium ulcerans is an emerging zoonotic pathogen that can cause diphtheria-like infections in humans. In this study, we report the novel detection and comprehensive phenotypic and genomic characterization of three atoxigenic C. ulcerans strains isolated from domestic animals in Brazil. Notably, all isolates belonged to the multilocus sequence type ST-339, which has been previously identified in both human and animal hosts from geographically distant regions, suggesting the potential for international dissemination. Whole-genome sequencing confirmed species identity and revealed high genetic simila-rity among isolates, although distinct phylogenetic subclades were observed. Genomic analyses identified conserved virulence-associated determinants, including incomplete pilus gene clusters, iron acquisition systems, and the pld gene encoding phospholipase D. In contrast, the tox gene was absent in all strains. Notably, one isolate exhibited ciproflo-xacin resistance associated with double mutations (S89L and D93G) in the quinolone- resistance-determining region of GyrA. Molecular modeling and dynamics simulations demonstrated that these mutations impair key interactions within the ciprofloxacin– magnesium–water complex, thereby compromising the stability of drug binding. Additionally, the presence of diverse mobile genetic elements, prophages, and CRISPR-Cas systems highlighted the genomic plasticity of these isolates. Our findings provide new insights into the zoonotic potential, antimicrobial resistance mechanisms, and genomic diversity of C. ulcerans, underscoring the need for strengthened surveillance and mole-cular monitoring of this emerging pathogen in both veterinary and public health contexts.

The essential oil extracted from Anemia tomentosa (EOAT) has shown larvicidal potential against Aedes aegypti, based on methods in vitro and in silico. Chromatographic and spectrometric techniques (gas chromatography-mass spectrometry (CG-MS), gas chromatography-flame ionization detector (GC-FID)), as well as mono and bidimensional nuclear magnetic resonance spectroscopy (NMR) were used to assess 10 essential oil components. Chemical composition of essential oil comprised 87.51% sesquiterpenes, with emphasis on presilphiperfolan-1-ol (42.13%) and silphiperfol-5-ene (19.47%). Larvicidal assay conducted in vitro with EOAT has evidenced potential cytotoxic activity up to 48 h exposure to it; mortality rate observed for A. aegypti larvae exposed to essential oil reached 100%. Study conducted in silico with chemical compounds deriving from the herein investigated plant species has evidenced its potential to inhibit acetylcholinesterase in A. aegypti. Activity of triquinane sesquiterpenes ranging from -6.8 to -8.2 kcal mol-1 stood out in comparison to that of temephos (-7.5 kcal mol-1). Chemical compounds identified in the investigated essential oil presented low human and environmental toxicity, as observed in absorption, distribution, metabolism and excretion, and toxicity (ADMETox) predictions.

Bredemeyera Willd. is a genus of the Polygalaceae family, occurring in Brazil. This research aims to evaluate the phytochemical and antifungal potential, in vitro and in silico, of Bredemeyera brevifolia extracts. The identification of fatty acids by gas chromatography-mass spectrometry and their quantification by gas chromatography-flame ionization detector showed that palmitic (36.55 mg g-1), margaric (3.66 mg g-1), linolelaidic (108.82 mg g-1), oleic (7.86 mg g-1), stearic (41.11 mg g-1), dihomo-γ-linolenic (85.48 mg g-1), and arachidic (209.00 mg g-1) acids are present in the hexane extract. From the chloroform extract, 1-hydroxy-3,7-dimethoxyxanthone was isolated and identified. The minimum inhibitory concentration assay with methanolic extract demonstrated antifungal activity against species of the genus Candida, Sporothrix, and Trichophyton for up to 96 h, with values ranging from 64-1024 μg mL-1. The in silico study with the chemical compounds of this species showed fungal inhibition potential of sterol14-α-demethylase, highlighting 1-hydroxy-3,7-dimethoxyxanthone, which presented an affinity energy of -8.8 kcal mol-1, greater than that observed for fluconazole (-8.3 kcal mol-1). The fatty acids interacted with the active site of the enzyme but presented energies ≥ -7.4 kcal mol-1. Compounds isolated from this species have pharmacokinetic potential for the development of pharmaceutical formulations.