Silver Nanoparticles from Cow’s Milk to Combat Multidrug-Resistant Gram-Negative Bacteria from Clinical Isolates

Abstract

The emergence of multidrug-resistant (MDR) bacteria is causing severe and lethal human infections and is posing a major threat in health care. Our previous study reports successful synthesis and characterization of silver nanoparticles (AgNPs) from pasteurized cow’s milk along with its potential antibacterial activity against non-MDR bacteria. The present research aims to study the antibacterial activity of AgNPs and its synergistic effects with five antibiotics (in regular clinical use) against the clinically isolated MDR bacteria such as Pseudomonas aeruginosa and Klebsiella pneumoniae. These bacteria were initially treated against 26 standard antibiotics to check the sensitivity using the Kirby–Bauer disc diffusion method. Results revealed that both organisms were resistant to all antibiotics tested and were MDR’s. Antibacterial studies indicated that cow’s milk AgNPs displayed effective inhibition zones ranging between 11–15 mm against P. aeruginosa and 8–10.5 mm against K. pneumoniae at 50 and 75 µl vis-a-vis control (source) and standard antibiotics where no inhibition zones were observed. Further, the synergistic effects of AgNPs with antibiotics revealed that maximum fold increase was obtained with piperacillin/tazobactam (4–5 folds) and co-trimoxazole (1.7–1.8 folds) against P. aeruginosa and K. pneumoniae respectively. Thus, AgNPs from pasteurised cow’s milk can be used as an effective antibacterial agent to combat the MDR’s and can be suggested as an alternative to antibiotics in the future.