Effects of Silver Nanoparticles on Multiple Drug-Resistant Strains of Staphylococcus aureus and Pseudomonas aeruginosa from Mastitis-Infected Goats: An Alternative Approach for Antimicrobial Therapy

Abstract

Recently, silver nanoparticles (AgNPs) have been widely used in various applications as antimicrobial agents, anticancer, diagnostics, biomarkers, cell labels, and drug delivery systems for the treatment of various diseases. Microorganisms generally acquire resistance to antibiotics through the course of antibacterial therapy. Multi-drug resistance (MDR) has become a growing problem in the treatment of infectious diseases, and the widespread use of broad-spectrum antibiotics has resulted in the development of antibiotic resistance by numerous human and animal bacterial pathogens. As a result, an increasing number of microorganisms are resistant to multiple antibiotics causing continuing economic losses in dairy farming. Therefore, there is an urgent need for the development of alternative, cost-effective, and efficient antimicrobial agents that overcome antimicrobial resistance. Here, AgNPs synthesized using the bio-molecule quercetin were characterized using various analytical techniques. The synthesized AgNPs were highly spherical in shape and had an average size of 11 nm. We evaluated the efficacy of synthesized AgNPs against two MDR pathogenic bacteria, namely, Pseudomonas aeruginosa and Staphylococcus aureus, which were isolated from milk samples produced by mastitis-infected goats. The minimum inhibitory concentrations (MICs) of AgNPs against P. aeruginosa and S. aureus were found to be 1 and 2 μg/mL, respectively. Our findings suggest that AgNPs exert antibacterial effects in a dose- and time-dependent manner. Results from the present study demonstrate that the antibacterial activity of AgNPs is due to the generation of reactive oxygen species (ROS), malondialdehyde (MDA), and leakage of proteins and sugars in bacterial cells. Results of the present study showed that AgNP-treated bacteria had significantly lower lactate dehydrogenase activity (LDH) and lower adenosine triphosphate (ATP) levels compared to the control. Furthermore, AgNP-treated bacteria showed downregulated expression of glutathione (GSH), upregulation of glutathione S-transferase (GST), and downregulation of both superoxide dismutase (SOD) and catalase (CAT). These physiological and biochemical measurements were consistently observed in AgNP-treated bacteria, thereby suggesting that AgNPs can induce bacterial cell death. Thus, the above results represent conclusive findings on the mechanism of action of AgNPs against different types of bacteria. This study also demonstrates the promising use of nanoparticles as antibacterial agents for use in the biotechnology and biomedical industry. Furthermore, this study is the first to propose the mode of action of AgNPs against MDR pathogens isolated from goats infected with subclinical mastitis.

Antibacterial effect of TiO2:Cu:Ag thin coatings on Pseudomonas strain measured by microbiological and ATP assays

“…The bacteriostatic effect and adaptation of Pseudomonas DSM50026 to the tested annealed nanomaterials could be explained by the ability of this bacterial species to activate special transport pumps for an export of the nanoparticles or ions out of the cell. This fact is a possible mechanism of stress response as other researchers have reported .…”

“…The doping of TiO 2 with Ag and Cu nanoparticles improved the photoresponse and photocurrent density of TiO 2 into the visible light region [21][22][23]. Other authors proved the several mechanisms of action of silver [17,18] and copper nanoparticles [16,20,21,24]. The combination of copper and silver nanoparticles leads to a stronger antibacterial effect at a lower concentration of eluted ions [25][26][27].…”

“…The results of SEM micrographs proved the membrane demolition after contact with the thin nanocomposite film and leakage of the cells content (Figure 4) [17][18][19]. The bacteriostatic effect and adaptation of Pseudomonas DSM50026 to the tested annealed nanomaterials could be explained by the ability of this bacterial species to activate special transport pumps for an export of the nanoparticles or ions out of the cell.…”

Visible Light Plasmon Excitation of Silver Nanoparticles Against Antibiotic-ResistantPseudomonas aeruginosa

“…Lately, a Trojan-horse like mechanism has been proposed, in which AgNPs first enter the cell and only then release silver ions (56). Previous studies showed that AgNPs promote the induction of reactive oxygen species (ROS) (57, 58) and enhance the expression of superoxide dismutase, catalase and peroxidase (58). These authors concluded that the main mechanism of antimicrobial action of AgNPs involves the disequilibrium of oxidation and antioxidation processes and the inability to eliminate ROS (58).…”

Transition metal complexes containing a tridentate cefadroxil‐based Schiff base: An effective paramagnetic semiquinone Ag (I) complex against Staphylococcus aureus and Pseudomonas aeruginosa

“…Because of this application, many methods and approaches concerning the synthesis of AgNPs, as well as silver‐based compounds containing ionic silver Ag (I) or metallic silver Ag (0) have been developed. Previously reported MIC values of AgNPs against P. aeruginosa and S. aureus were found to be 0.6–3 μg ml −1 and 0.8–7 μg ml −1 , respectively, using AgNPs in the size range between 5 and 30 nm . Because of higher surface area and more effective binding to the bacterial membrane, smaller AgNPs are considered to be more effective than larger particles.…”