Identification of bacterial susceptibility to antibiotics using gold nanoparticles

Inexpensive and rapid bacterial detection and antimicrobial susceptibility assays are desperately needed, as the determination of which antibiotic to use and its administration at effective dosages is critical. Currently, the assessment of antimicrobial susceptibility takes 24 to 48 hours. Hence, we have developed a nanoparticle-based antimicrobial susceptibility assay, utilizing the Concanavalin A-induced clustering of dextran-coated gold nanoparticles. When the bacteria do not grow, addition of Concanavalin A promotes the formation of extensive dextran gold nanoassemblies. The induction of these nanoassemblies is mediated by the presence of free carbohydrates, causing large shifts in the nanoparticles’ surface plasmon band. In contrast, when the bacteria grow, the levels of free carbohydrates decrease, thus the size of the gold nanoparticle clusters and the plasmonic shifts are smaller. This gold nanoparticle-based assay provides results within 3 hours and can be used for the high-throughput screening of samples during epidemics.