Differentiation of outer membrane proteins from Salmonella enterica serotypes using Fourier transform infrared spectroscopy and chemometrics

Aims:  To differentiate between outer membrane proteins (OMPs) from six Salmonella enterica serotypes using a Fourier transform infrared (FTIR) spectroscopy method and chemometrics. Methods and Results:  The OMPs from Salmonella serotypes (Typhimurium, Enteritidis, Thomasville, Hadar, Seftenberg and Brandenburg) were isolated using a sarcosyl extraction method. OMP profiles on SDS‐PAGE exhibited two or three bands between 48 and 54 kDa. Spectra of 10  μ l of OMP preparations (5 mg ml −1 ) dried on a gold reflective slide were collected using 128 scans at 4 cm −1 resolution and units of log (1/R) and analyzed using canonical variate analysis (CVA) and linear discriminant analysis (LDA). The CVA of Salmonella OMP spectra in the 1800–1500 cm −1 region separated the serotypes and LDA provided a 100% correct classification. Conclusions:  The use of a FTIR method combined with chemometrics provided better differentiation of Salmonella OMPs than the OMP pattern analysis by SDS‐PAGE. Significance and Impact of the Study:  This is the first study to demonstrate that spectra of OMP extracts from Salmonella serotypes can be used for 100% correct classification of the serotypes studied.