Background: Klebsiella pneumoniae is a major multidrug-resistant pathogen associated with severe hospital-acquired infections. Although meropenem remains a key therapeutic option, little is known about the global transcriptional response of K. pneumoniae to carbapenem exposure, especially in clinical isolates. Methods: We performed RNA-sequencing (RNA-seq) on an extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae strain exposed to meropenem at clinically relevant serum concentrations. Differentially expressed genes were identified and mapped onto central metabolic pathways. Results: Meropenem exposure triggered a profound transcriptional reprogramming. Glycolytic genes were significantly upregulated, including hexokinase, phosphoglycerate kinase, and pyruvate kinase, suggesting increased energy production via substrate-level phosphorylation. In contrast, genes in the oxidative branch of the tricarboxylic acid (TCA) cycle, such as succinate dehydrogenase and isocitrate dehydrogenase, were downregulated. Several amino acid biosynthetic pathways—including those for glutamate, serine, arginine, methionine, and branched-chain amino acids—were transcriptionally activated, indicating a shift toward anabolism and redox balance. Conclusion: Our findings reveal a coordinated metabolic adaptation in K. pneumoniae under meropenem stress, characterized by enhanced glycolysis and amino acid biosynthesis alongside partial TCA suppression. This Warburg-like phenotype may support bacterial survival, stress tolerance, and early persistence. These insights offer new perspectives on noncanonical antibiotic response pathways and potential metabolic targets for therapeutic intervention.

Introduction: Silver nanoparticles have been extensively investigated in dental and orthopedic materials. However, the impregnation of bone graft with silver nanoparticles has been poorly investigated. Objectives: The aim of this study was to evaluate the in vitro antibiofilm activity of a bovine bone impregnated with silver nanoparticles. Methods: Bone scaffolds from cancellous bovine femur were used for the tests and impregnated with silver nanoparticles (50nm) by physical adsorption. Silver nitrate minimal inhibitory and bactericidal concentration were performed Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, Enterococcus faecalis, Acinetobacter baumannii, and Escherichia coli. Disc diffusion tests for silver nanoparticles susceptibility and quantification of biofilm production on plate and bone with sessile cell count were also performed. Results: All pathogens were susceptible to silver with low minimal inhibitory concentration (0.25 – 4 mg/L). The scaffold impregnated with silver nanoparticles presented a significant reduction in the biofilm cells for all microorganisms with a reduction of more than 3 logs in colony forming units count. Conclusion: Bone scaffolds impregnated with silver nanoparticles can significantly reduce biofilm, and it can be a strategical material to be used as an implant for different approaches.

Background: Ventilator-associated pneumonia (VAP) is one of the most common causes of nosocomial infections and is associated with prolonged hospitalization, increased health care costs, and high mortality of critically ill patients during hospitalization in intensive care units (ICUs). Objective: To characterize and evaluate in vitro and in vivo antimicrobial and anti-biofilm activity of an in-house tracheostomy tube impregnated with chlorhexidine and violet crystal. Methods: The tracheostomy tubes were tested in vitro for their ability to prevent biofilm formation by standard strains of S. aureus, P. aeruginosa, and E. coli, and multidrug-resistant bacteria obtained from clinical cultures: Meticillin-resistant S. aureus (MRSA), and carbapenem-resistant Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae. Results: The impregnated tracheostomy tubes demonstrated antimicrobial activity, including for multidrug-resistant bacteria. In this pilot study, 14 patients were evaluated, seven in the chlorhexidine and violet crystal-coated group and seven in the control group. During ventilation, VAP occurred in one patient in the coated group and in three patients in the control group (p=0.28). The biomass in the impregnated tubes did not differ from the control group and no difference was found in the production of sessile cells by the quantitative method, with a median of 15.50 cfu/mL (IQR25-75% 12.00-196.50) and 168.00 cfu/mL ((IQR25-75% 78.50-250.00), respectively. Conclusion: This study provides preliminary evidence to support that antiseptic impregnation of tracheostomy tube provides significant antimicrobial activity.