A rapid tag-free identification of: Escherichia coli antibiotic-resistant isolates using Raman scattering

Rapid and accurate detection of pathogenic bacteria is a critical issue for public health and food safety. We introduce a rapid tag-free identification method for subtyping clinically relevant human blood-cultured Escherichia coli (E. coli) colonies. Gold-deposited surface-enhanced Raman scattering (SERS)-functionalized substrates were used to identify seven E. coli isolates. The method achieved a rapid analysis time of 30 min, an enhancement factor of 1.6 × 10⁴ to Raman intensities, and high reproducibility with approximately 5% relative standard deviation. The proposed SERS procedure coupled with a multivariate statistics-supported classification method showed good performance compared to previous procedures. Therefore, the SERS-based tag-free identification method has high potential for rapidly subtyping clinically relevant quinolone-resistant E. coli antibiotic-resistant isolates. In future, the SERS-based biosensing technique may be applied in the clinical laboratory using a portable Raman machine and optic probe Raman system.