Rapid, direct, visualized and antibody-free bacterial detection with extra species identification and susceptibility evaluation capabilities

Bacterial antimicrobial resistance (AMR) driven by the abuse of antibiotics is a global highlight challenge, calling for a rapid, economical and generalizable bacterial detection technology. Here, in case of urinary tract infections (UTIs), a naked-eye, antibody-free and multi-functional bacterial assessment platform was designed, which consisted of concanavalin A modified gold nanoparticles (ConA-AuNPs), vancomycin modified gold nanoparticles (Van-AuNPs), and polymyxin B modified Prussian blue nanoparticles (PMB-PBNPs). Based on the fast agglutination of bacterial cells induced by concanavalin A, ConA-AuNPs could aggregate on bacterial cells of Escherichia coli and Staphylococcus aureus, resulting in a visible color change due to alteration of surface plasmon resonance properties within 30 min. Besides, due to the different affinity of vancomycin and polymyxin B to bacteria, Van-AuNPs preferred to bind to Gram-positive bacteria, generating colorimetric response within 2-3 h; while PMB-PBNPs could be reduced colourless Prussian white (PW) by the prior Gram-negative bacterial metabolization in contrast to Gram-positive bacterial metabolization within 4-6 h. Combining our platform with antibiotics, the minimum inhibitory concentration of bacteria could be determined within 4-8 h, which was proved by incubating Escherichia coli and Staphylococcus aureus with various antibiotics. The feasibility was verified by clinical samples, which was consistent with the classical clinical test within only 1/48 of the process timing. Therefore, this colorimetric nanoplatform orderly realized the rapid detection, species identification (Gram-positive and Gram-negative), and susceptibility evaluation of bacteria, satisfying multiple needs from timely clinical diagnosis to accurate medication guidance.