Biofilm Eradication Using Biogenic Silver Nanoparticles.

Microorganisms offer an alternative green and scalable technology for the synthesis of value added products. Fungi secrete high quantities of bioactive substances, which play dual-functional roles as both reducing and stabilizing agents in the synthesis of colloidal metal nanoparticles such as silver nanoparticles, which display potent antimicrobial properties that can be harnessed for a number of industrial applications. The aim of this work was the production of silver nanoparticles using the extracellular cell free extracts of Phanerochaete chrysosporium, and to evaluate their activity as antimicrobial and antibiofilm agents. The 45-nm diameter silver nanoparticles synthesized using this methodology possessed a high negative surface charge close to -30 mV and showed colloidal stability from pH 3-9 and under conditions of high ionic strength ([NaCl] = 10-500 mM). A combination of environmental SEM, TEM, and confocal Raman microscopy was used to study the nanoparticle-E. coli interactions to gain a first insight into their antimicrobial mechanisms. Raman data demonstrate a significant decrease in the fatty acid content of E. coli cells, which suggests a loss of the cell membrane integrity after exposure to the PchNPs, which is also commensurate with ESEM and TEM images. Additionally, these biogenic PchNPs displayed biofilm disruption activity for the eradication of E. coli and C. albicans biofilms.

Biogenic Silver Nanoparticles as a Strategy in the Fight Against Multi-Resistant Salmonella enterica Isolated From Dairy Calves.

Infectious diseases are one of the most important health problems worldwide, one of the main causes being the development of multi-resistant microorganisms. Likewise, the zoonotic potential of some pathogens and their ability to transfer resistance mechanisms, reduce the therapeutic options in both humans and animals. Salmonella enterica is an important pathogen that affects a wide range of animal species and humans, being Salmonella Typhimurium one of the most frequent serotypes affecting cattle, causing enteritis, diarrhea, and septicemia. The search for alternative therapeutic approaches has gained importance since the emergence of multidrug resistance to antibiotics and periodic outbreaks of salmonellosis. In this sense, the discovery of new drugs and the development of new strategies, such as the use of nanoparticles with antimicrobial activity, are very promising. The aim of this work was the extracellular production of biogenic silver nanoparticles using fungal extracts and the evaluation of their antimicrobial activity against resistant and multi-resistant Salmonella Typhimurium strains. We here demonstrated the potential of the biogenic nanoparticles as effective bacteriostatic and bactericidal agents for use in biomedical applications. In addition, Confocal Raman Microscopy and Atomic Force Microscopy were used to advance the understanding of the antimicrobial mechanism of biogenic nanoparticles against these pathogenic strains, the results of which suggested that the nanoparticles produced damage in several bacterial cell structures.