Salmonella ser. Enteritidis, Salmonella ser. Typhimurium/4,[5],12:i:- and Salmonella ser. Typhi biomarkers detection using Biotyper MicroFlex LT and VITEK MS PRIME platforms in Argentina

Salmonella genus includes around 2600 serovars, causing important zoonotic diseases and enteric fever, with significant impact on public health worldwide. Serovar characterization is commonly achieved by phenotypic and genotypic tests, requiring several days to obtain a result. Mass spectrometry (MS) only allows identification of Salmonella isolates at the genus level. Our aim was to evaluate the performance of MS for Salmonella ser. Enteritidis (SE), Salmonella ser. Typhimurium (STM)/4,[5],12:i:- and Salmonella ser. Typhi (ST) specific-serovar biomarker detection. We included 257 isolates from 34 different serovars (62 SE, 69 STM/4,[5],12:i:-, 17 ST) for analysis of spectra obtained by the direct method, using CHCA as matrix. For acquisition, we used Biotyper MicroFlex LT (Bruker Daltonics) and VITEK MS PRIME (BioMérieux) platforms, and performed a manual search for previously described biomarkers. Using Biotyper MicroFlex LT, sensitivity (Se) for the 3016Da and 6036Da SE biomarkers was 85% and 95%, respectively (specificity (Sp)=100%). The Se for the STM/4,[5],12:i:- biomarker (7095Da) was 100% and the Sp=98%. For ST biomarker (5710Da), Se and Sp were 88% and 100%, respectively. For VITEK MS PRIME, Se for the 3018Da SE biomarker was 42% and for the 6036Da was 79% (Sp=100% for both); for the STM/4,[5],12:i:- biomarker (7096Da), Se was 83% and Sp=97%; and for the ST biomarker (5712Da), Se=94% and Sp=100%. The identification of these frequent serovars can be expedited using MALDI-TOF MS technology. The rapid and reliable diagnosis of salmonellosis can have a positive impact on patient outcomes and public health.