Fig. 2

The average spectra of P. insidiosum with treated and control groups. a The raw average spectra model (upper lines) derived from P. insidiosum with an organic solvent as the negative control (green), P. insidiosum treated by thimerosal as the positive control (sky blue) and P. insidiosum with the three differences treated by xanthyletin (carmine) and anti-P. insidiosum substances that extracted from P. stutzeri ST1302 (navy) and K. pneumoniae ST2501 (red) showed the pattern of the whole spectrum (4000–900 cm^− 1). All the average spectra from the second derivative and EMSC processing (lower lines) demonstrated the different regions in the spectral range of 1800–1500 cm^− 1 (protein region) and 1500–1200 cm^− 1 (mixed region). b Enlarging image at the average spectral range 1900–900 cm^− 1 revealed clearly differences points in proteins and mixed regions of the spectra which managed by the second derivative and EMSC, whereas the raw average spectra were not seen