Application of Fourier transform infrared spectroscopy and chemometrics for differentiation of Salmonella enterica serovar Enteritidis phage types

摘要

Fourier transform infrared (FT-IR) spectroscopy and chemometric techniques were used to discriminate fiveclosely related Salmonella enterica serotype Enteritidis phage types, phage type 1 (PT1), PT1b, PT4b, PT6, andPT6a. Intact cells and outer membrane protein (OMP) extracts from bacterial cell membranes were subjectedto FT-IR analysis in transmittance mode. Spectra were collected over a wavenumber range from 4,000 to 600cm 1. Partial least-squares discriminant analysis (PLS-DA) was used to develop calibration models based onpreprocessed FT-IR spectra. The analysis based on OMP extracts provided greater separation between theSalmonella Enteritidis PT1-PT1b, PT4b, and PT6-PT6a groups than the intact cell analysis. When these threephage type groups were considered, the method based on OMP extract FT-IR spectra was 100% accurate.Moreover, complementary local models that considered only the PT1-PT1b and PT6-PT6a groups weredeveloped, and the level of discrimination increased. PT1 and PT1b isolates were differentiated successfullywith the local model using the entire OMP extract spectrum (98.3% correct predictions), whereas the accuracyof discrimination between PT6 and PT6a isolates was 86.0%. Isolates belonging to different phage types (PT19,PT20, and PT21) were used with the model to test its robustness. For the first time it was demonstrated thatFT-IR analysis of OMP extracts can be used for construction of robust models that allow fast and accuratediscrimination of different Salmonella Enteritidis phage types.