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

Aims: To differentiate between outer membrane proteins (OMPs) from six Salmonellaenterica serotypes using a Fourier transform infrared (FTIR) spectroscopy method and chemometrics. Methods: 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 mu 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. Conclusios: 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 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.