Antibacterial and Biofilm Modulating Potential of Ferulic Acid-Grafted Chitosan against Human Pathogenic Bacteria

The emergence of more virulent forms of human pathogenic bacteria with multi-drug resistance is a serious global issue and requires alternative control strategies. The current study focused on investigating the antibacterial and antibiofilm potential of ferulic acid-grafted chitosan (CFA) against Listeria monocytogenes (LM), Pseudomonas aeruginosa (PA), and Staphylococcus aureus (SA). The result showed that CFA at 64 µg/mL concentration exhibits bactericidal action against LM and SA (>4 log reduction) and bacteriostatic action against PA (<2 log colony forming units/mL reduction) within 24 h of incubation. Further studies based on propidium iodide uptake assay, measurement of material released from the cell, and electron microscopic analysis revealed that the bactericidal action of CFA was due to altered membrane integrity and permeability. CFA dose dependently inhibited biofilm formation (52–89% range), metabolic activity (30.8–75.1% range) and eradicated mature biofilms, and reduced viability (71–82% range) of the test bacteria. Also, the swarming motility of LM was differentially affected at sub-minimum inhibitory concentration (MIC) concentrations of CFA. In the present study, the ability of CFA to kill and alter the virulence production in human pathogenic bacteria will offer insights into a new scope for the application of these biomaterials in healthcare to effectively treat bacterial infections

Antibacterial activity of Staphylococcus aureus biofilm under combined exposure of glutaraldehyde, near-infrared light, and 405-nm laser.

Healthcare-associated infections have increasingly become problematic in the endoscopic procedures resulting in several severe diseases such as carbapenem-resistant Enterobacteriaceae (CRE)-related infections, pneumonia, and bacteremia. Especially, some bacterial strains are resistant to traditional antimicrobials. Therefore, the necessity of developing new antibiotics or management to deal with bacterial infections has been increasing. The current study combined a low concentration of glutaraldehyde (GTA) with near-infrared (NIR) light and 405-nm laser to entail antibacterial activity on Staphylococcus aureus biofilm. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and colony forming unit (CFU) counting were used to quantify the viable cells while fluorescent and scanning electron microscopic images were used to qualitatively evaluate the cell membrane integrity and structural deformation, respectively. Practically, S. aureus biofilm was highly susceptible (7% cell viability and 6.8-log CFU/cm2 bacterial reduction for MTT assay and CFU analysis, respectively) to the combination of GTA (0.1%), NIR light (270 J/cm2), and 405-nm laser (288 J/cm2) exposure. GTA could form either DNA-protein or protein-protein crosslinks to inhibit DNA and protein synthesis. The NIR light induced the thermal damage on protein/enzymes while 405-nm laser could induce reactive oxygen species (ROS) to damage the bacterial membrane. Thus, the proposed technique may be a feasible modality for endoscope cleaning to prevent any secondary infection in the healthcare industry