Characterization of Salmonella spp. Based on CRISPR PCR and FT-IR Approaches: A Pilot Study in Northern Italy

The aim of the present study was to employ a genotypic method (CRISPR PCR) and a phenotypic method (FT-IR combined with Linear Discriminant Analysis, LDA) for the rapid identification and discrimination of major virulent Salmonella serovars. Specifically, a total of 24 Salmonella Enteritidis, 24 Salmonella Typhimurium, 24 S. Typhimurium 4,5,12:i:-, and 14 Salmonella Infantis strains, previously serotyped according to the Kaufmann-White scheme, were analyzed. CRISPR PCR generated serotype-specific amplicons: 850 bp for S. Enteritidis, 700 bp and 2000 bp for S. Typhimurium, 1300 bp and 1500 bp for S. Typhimurium 4,5,12:i:-, and 1000 bp and 1900 bp for S. Infantis. FT-IR spectra of all serotypes were analyzed by LDA, which revealed a clear separation of three serotype-defined groups: S. Enteritidis, S. Infantis, and a group comprising S. Typhimurium and its monophasic variant 4,5,12:i:-. Further discrimination based on CRISPR-defined classes was observed within each serovar: two classes for S. Typhimurium, two for S. Typhimurium 4,5,12:i:-, and three for S. Infantis. Overall, the combined CRISPR PCR and FT-IR-LDA approach provides preliminary evidence supporting the potential application of a combined approach for the epidemiological surveillance of Salmonella.