摘要： Rapid detection and discrimination of pathogenic bacteria for food safety, environmental pollution, medical diagnoses, and chemical and biological threats remains a considerable challenge. In the present work, we demonstrate positively charged Ag/Au bimetallic nanoparticles (Ag/Au bmNPs) as a potential surface-enhanced Raman scattering (SERS) substrate for label-free detection and discrimination of three bacteria, viz., Escherichia coli, Salmonella typhimurium and Bacillus subtilis with excellent reproducibility. The approach relies on a priori synthesis of Ag/Au bmNPs and subsequent SERS studies on bacteria. The positive surface charge on Ag/Au bmNPs offers significant advantages of short acquisition time at very low power, high sensitivity, and simple operating procedure without the need of very specific procedures/protocols used to capture the bacteria. The reproducible and specific intrinsic fingerprint of the cell wall and intracellular components of three bacteria obtained by label-free SERS enables precise discrimination and classification of three bacteria using multivariate analysis such as principal component analysis and canonical discriminant analysis.