Biogenic Silver Nanoparticles: An Antibacterial and Antibiofilm Approach to Control Carbapenem-Resistant Klebsiella pneumoniae

The increasing resistance of Klebsiella pneumoniae to antibiotics, particularly carbapenems, underscores the urgent need for alternative antimicrobial strategies. This study aimed to evaluate the antimicrobial and antibiofilm activity of biogenic silver nanoparticles (Bio-AgNPs), synthesized using Trichilia catigua extract and to investigate their mechanism of action on bacterial cells. The antimicrobial efficacy of Bio-AgNPs was assessed by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and through susceptibility assays, time-kill analysis, flow cytometry, and electron microscopy. Bio-AgNPs exhibited strong antibacterial activity against all tested K. pneumoniae strains, with MICs ranging from 0.49 to 15.62 µg/mL. Eradication of biofilms required concentrations 16 to 64 times higher than those effective against planktonic cells, highlighting the protective nature of biofilm matrix. Time-kill assays showed a concentration-dependent bactericidal effect, with 4xMIC rapidly eliminating viable cells. Flow cytometry indicated membrane destabilization, increased fluidity at lower concentrations, and extensive structural damage at higher concentrations. Although lipid peroxidation and reactive oxygen species (ROS) were detected, they were not statistically significant, suggesting that membrane disruption is the primary bactericidal mechanism. Electron microscopy corroborated the structural disintegration of both bacterial cells and biofilms after treatment. Bio-AgNPs demonstrated potent antimicrobial and antibiofilm effects against multidrug-resistant K. pneumoniae, with membrane damage as the main mechanism of action. These results support the potential application of Bio-AgNPs as a therapeutic alternative for biofilm-associated infections. This study highlights the antibacterial and anti-biofilm potential of biogenic silver nanoparticles (Bio-AgNPs) as an effective tool against multidrug-resistant Klebsiella pneumoniae, with efficancy against both free-living cells and structured biofilms.