ASSESSMENT OF SILVER NANOPARTICLES AS TARGETED ANTIMICROBIAL AGENTS AGAINST E. COLI IN VETERINARY URINARY TRACT INFECTIONS

Abstract

The increasing case of multidrug-resistant (MDR) Escherichia coli in veterinary urinary tract infections (UTIs) has significantly hindered the ability to effectively treat the infection, and thus, there is an urgent requirement for alternative antimicrobial treatment. Although silver nanoparticles (AgNPs) hold a broad-spectrum promise, their applicability against clinically significant veterinary isolates, especially against biofilm-mediated resistance, and their safety, was poorly developed. The objective of the study was to evaluate in detail the antimicrobial properties and the in vitro safety of AgNPs in response to a characterised panel of MDR E. coli in veterinary UTIs. We selected 150 E. coli strains, identified their antibiotic resistance profiles, and tested AgNPs in terms of minimum inhibitory concentration (MIC), time-kill kinetics, and biofilm inhibition. The cytotoxicity and hemolytic activity were evaluated towards the mammalian renal cells and erythrocytes. AgNPs showed uniform efficacy (MIC 90 =16 μg/mL) regardless of MDR, ESBL-production, or antibiotic resistance pattern (p > 0.05), with bactericidal effect of 4 hours. They were highly active against biofilm formation with a maximum of 91% at MIC, with a high selectivity index (18.7) and low cytotoxicity. Importantly, biofilm strength was the only strong predictor of less susceptibility to AgNP (aOR: 4.05, p < 0.0001). The results validate the assertion that AgNPs are effective against MDR veterinary isolates using a multimodal system and have an excellent safety profile, which underscores the high potential as a new therapeutic agent to manage antimicrobial-resistant veterinary UTIs.