Bacteria mediated silver nanoparticles: comparison as potent antibiofilm agents

Introduction: Biosynthesized silver nanoparticles (AgNPs) have good antimicrobial properties comparable to chemically synthesized silver nanoparticles. Further, they have good potential as antibiofilm agents.

Methods: AgNPs were synthesized from Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923) and Acinetobacter baumannii (confirmed clinical isolate) and physically characterized by several techniques. The antibiofilm activity of the AgNPs against biofilms of P. aeruginosa, S. aureus and C. albicans was studied using crystal violet assay. Biofilms were formed in 96-well polystyrene plates and treated with biosynthesized AgNPs for 24 and 48 h.

Results: AgNPs synthesized by all bacteria except S. aureus mediated AgNPs displayed 50% biofilm inhibition at AgNP concentrations between 1.98 - 0.225 mg/ml. S. aureus mediated AgNPs showed 50% biofilm inhibition only against S. aureus biofilm. Scanning Electron microscopic images indicated that biosynthesized AgNPs were able to decrease surface coverage of biofilms and to reduce the extracellular matrix causing morphological changes in biofilms noticeably.

Conclusion: This study reports the antibiofilm activity of bacteria mediated AgNPs. This is the first report on antibiofilm activity of AgNPs synthesized by Acinetobacter baumannii and also as a comparison of antibiofilm activity of several bacteria mediated AgNPs. According to the results, low dosages of green AgNPs can be applied in treating drug-resistant microbial infections in a cost effective manner. In conclusion, the bacterial synthesized AgNPs have antibiofilm activity and good stability suggesting its usefulness as economic and environmental friendly antibiofilm agents.