Improved Biofilm Antimicrobial Activity of Polyethylene Glycol Conjugated Tobramycin Compared to Tobramycin in Pseudomonas aeruginosa Biofilms

Antibiotic-loaded MoS2 nanosheets to combat bacterial resistance via biofilm inhibition

The emergence of antibiotic resistance has resulted in increasing difficulty in treating clinical infections associated with biofilm formation, one of the key processes in turn contributing to enhanced antibiotic resistance. With the rapid development of nanotechnology, a new way to overcome antibiotic resistance has opened up. Based on the many and diverse properties of MoS2 nanosheets that have attracted wide attention, in particular their antibacterial potential, herein, a novel antimicrobial agent to combat resistant gram-positive Staphylococcus aureus and gram-negative Salmonella was prepared using chitosan functionalized MoS2 nanosheets loading tetracycline hydrochloride drugs (abbreviated to CM-TH). The antibacterial and anti-biofilm activities of the CM-TH nanocomposites showed the synergetic effect that the combination of nanomaterials and antibiotics was more efficient than either working alone. In particularly, the minimum inhibitory concentration values generally decreased by a factor of dozens, suggesting that CM-TH may become a possible alternative to traditional antibiotics in disrupting biofilms and overcoming antibiotic resistance in treating medical diseases.

Structure-Activity Relationship of Membrane-Targeting Cationic Ligands on a Silver Nanoparticle Surface in an Antibiotic-Resistant Antibacterial and Antibiofilm Activity Assay

To explore the structure-activity relationship of membrane-targeting cationic ligands on a silver nanoparticle surface in an antibiotic-resistant antibacterial and antibiofilm activity assay, a series of functionalized silver nanocomposites were synthesized. Tuning the structural configuration, molecular weight, and side-chain length of the cationic ligands on the nanoparticle surface provided silver nanocomposites with effective antibacterial activity against both antibiotic-resistant Gram-negative and Gram-positive bacteria, including bacterial biofilms. These silver nanocomposites did not trigger hemolytic activity. Significantly, the bacteria did not develop resistance to the obtained nanocomposites even after 30 generations. A study of the antibacterial mechanism confirmed that these nanocomposites could irreversibly disrupt the membrane structure of bacteria and effectively inhibit intracellular enzyme activity, ultimately leading to bacterial death. The silver nanocomposites (64 μg/mL) could eradicate 80% of an established antibiotic-resistant bacterial biofilm. The strong structure-activity relationship toward antibacterial and antibiofilm activity suggests that variations in the conformational property of the functional ligand could be valuable in the discovery of new nano-antibacterial agents for treating pathogenic bacterial infections.

3-Amino-4-aminoximidofurazan derivatives: small molecules possessing antimicrobial and antibiofilm activity against Staphylococcus aureus and Pseudomonas aeruginosa

AIM

The therapeutic treatment of microbial infections involving biofilm becomes quite challenging because of its increasing antibiotic resistance capacities. Towards this direction, in the present study we have evaluated the antibiofilm property of synthesized 3-amino-4-aminoximidofurazan compounds having polyamine skeleton. These derivatives were synthesized by incorporating furazan and biguanide moieties.

METHODS AND RESULTS

Different 3-amino-4-aminoximidofurazan derivatives (PI1-4) were synthesized via protic acid catalysis and subsequently characterized by (1) H NMR and (13) C NMR spectra, recorded at 400 and 100 MHz respectively. We have tested the antimicrobial and antibiofilm activities of these synthetic derivatives (PI1-4) against both Staphylococcus aureus and Pseudomonas aeruginosa. The compounds so tested were also compared with standard antibiotics namely Tobramycin (Ps. aeruginosa) and Azithromycin (Staph. aureus) which were used as a positive control in all experimental sets. All these compounds (PI1-4) exhibited moderate to significant antimicrobial activities against both micro-organisms wherein compound PI3 showed maximum activity. Biofilm inhibition of both micro-organisms was then evaluated by crystal violet and safranin staining, estimation of biofilm total protein and microscopy methods using sub-MIC dose of these compounds. Results showed that all compounds executed anti biofilm activity against both Staph. aureus and Ps. aeruginosa wherein compound PI3 exhibited maximum activity. In relation with microbial biofilm inhibition, we have observed reduction in bacterial motility, proteolytic activity and secreted exo-polysaccharide (EPS) from both Staph. aureus and Ps. aeruginosa when they were grown in presence of these compounds. While addressing the issue of toxicity on host, we have observed that these molecules exhibited minimum level of R.B.C degradation.

CONCLUSION

These findings establish the antibacterial and anti biofilm properties of 3-amino-4-aminoximidofurazan derivatives (PI1-4).

SIGNIFICANCE AND IMPACT OF THE STUDY

Therefore, our current findings demonstrate that 3-amino-4-aminoximidofurazan derivatives (PI1-4) may hold promise to be effective biofilm and microbial inhibitors that may be clinically significant.

Antimicrobial Polymers and Surfaces – Natural Mimics or Surpassing Nature?

Fighting pathogenic microbes is one of the great current challenges of mankind. Nature has developed several techniques to counteract microbial attacks. Science has also yielded several technologies, including antimicrobial polymers as biocides and polymers used for microbe killing and repelling surfaces. Recent scientific antimicrobial approaches are mimicking natural concepts. In this chapter, current developments in antimicrobial and antifouling polymers and surfaces are reviewed and discussed regarding the question whether they mimic nature or surpass it.

Potent Antibacterial Nanoparticles against Biofilm and Intracellular Bacteria

The chronic infections related to biofilm and intracellular bacteria are always hard to be cured because of their inherent resistance to both antimicrobial agents and host defenses. Herein we develop a facile approach to overcome the above conundrum through phosphatidylcholine-decorated Au nanoparticles loaded with gentamicin (GPA NPs). The nanoparticles were characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS) and ultraviolet−visible (UV−vis) absorption spectra which demonstrated that GPA NPs with a diameter of approximately 180 nm were uniform. The loading manner and release behaviors were also investigated. The generated GPA NPs maintained their antibiotic activities against planktonic bacteria, but more effective to damage established biofilms and inhibited biofilm formation of pathogens including Gram-positive and Gram-negative bacteria. In addition, GPA NPs were observed to be nontoxic to RAW 264.7 cells and readily engulfed by the macrophages, which facilitated the killing of intracellular bacteria in infected macrophages. These results suggested GPA NPs might be a promising antibacterial agent for effective treatment of chronic infections due to microbial biofilm and intracellular bacteria.