Rapid discrimination of Salmonella Enteritidis from other serovars with MALDI-TOF MS in Argentina

Salmonella spp. is one of the most important zoonotic pathogens that causes foodborne diseases. It is divided into two species (Salmonella bongori and Salmonella enterica) including around 2600 serovars, being S. enterica serovar Enteritidis one of the most frequent in Argentina. Serovar identification is generally conducted by somatic and flagellar agglutination sera assays, and molecular biology techniques can also be performed. As efforts are being made worldwide to differentiate Salmonella serovars, our aim was to evaluate the utility of two specific biomarkers, previously reported for differentiating S. Enteritidis with MALDI-TOF MS. A panel of 105 S. enterica local isolates, belonging to different serovars and characterized by sera agglutination and PCR, was included in this study. Two specific S. Enteritidis biomarkers, at m/z 3016±3Da and 6034±3Da, were visually detected showing a sensitivity of 54% and 98%, respectively, and a specificity of 100% for both peaks. Concordance between serotyping and identification by PCR of S. Enteritidis and the blind search of biomarkers in a subset of isolates was 98%. Visual detection of these S. Enteritidis biomarkers using MALDI-TOF MS can be used as a fast and easy screening method for serovars differentiation at the microbiology clinical laboratory.