Figure 3. Evolution of SERS spectra for imipenem-susceptible and -resistant E. coli with and without imipenem treatment.

(a) E. coli (ATCC 25922); (b) clinical isolate of imipenem-resistant E. coli with (red curves) and without (black curves) imipenem treatment; (c) signal ratio of 654-cm⁻¹ SERS peak (r₆₅₄) of E. coli (ATCC 25922) as a function of imipenem treatment time; (d) r₆₅₄ of imipenem-resistant E. coli as a function of imipenem treatment time; (e) signal ratio of 724-cm⁻¹ SERS peak (r₇₂₄) of E. coli (ATCC 25922) as a function of imipenem treatment time; (f) r₇₂₄ of imipenem-resistant E. coli as a function of imipenem treatment time. Black and red curves represent the mean SERS spectra, while gray and light red curves represent their corresponding standard deviation.