Gold nanocluster-based biosensing for rapid detection of carbapenem-resistant organisms in bloodstream infections

Carbapenem resistance in Gram-negative bacteria poses a critical global health challenge, particularly in the context of bloodstream infections (BSIs) where treatment options are severely limited and diagnostic delays can be fatal. Existing methods for detecting carbapenem resistant organisms (CROs) often lack the speed, sensitivity, and specificity required for timely clinical intervention, and currently, no validated approach exists for direct detection from blood samples. In this study, we introduce a novel diagnostic strategy utilizing bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs), which exhibit a strong fluorescence emission and average size of 2.9 nm. This method enabled rapid detection of carbapenem resistance among 400 Gram-negative clinical isolates, with 97 confirmed resistant by both phenotypic and genotypic analyses. Real-time PCR revealed NDM and VIM as the most common resistance genes, followed by OXA-48, IMP, and KPC. The BSA-AuNC assay detected as few as 10 CFU/mL in cultured isolates within 1.5 h, achieving 100% positive and negative predictive values. Remarkably, when applied directly to centrifuged blood samples, the assay maintained a high sensitivity of 95.8% with a detection limit of 1000 CFU/mL in under 2 h, outperforming the Carba NP test, which showed only 85.56% sensitivity. These findings highlight the potential of BSA-AuNCs as a rapid, sensitive, and culture-independent tool for early identification of carbapenem-resistant organisms in BSIs, offering critical support for timely and effective clinical decision-making.