Proteomic characterization of outbreak-associated Listeria monocytogenes strains in Italy: discovery of virulence markers

Listeria monocytogenes, a persistent foodborne pathogen associated with ready-to-eat (RTE) foods, remains a significant threat to food safety and consumer health, particularly for vulnerable populations. This research delves into the proteomic analysis of hypervirulent L. monocytogenes strains from meat-based foods to better understand their pathogenicity, virulence, and adaptation under stress conditions. We used immunoproteomics and bioinformatics to characterize the immunogenic protein profile of an ST7 strain linked to severe listeriosis outbreaks in central Italy (Chiaverini et al., 2021). Our findings showed that L. monocytogenes produces several immunogenic proteins in response to mild acid, high osmolarity, and low temperature stress conditions (D"Onofrio et al., 2022). Six specific proteins were identified, related to cell motility (FliM, lmo0723), carbohydrate metabolism (PdhB), oxidative stress (TrxB, lmo2679), and DNA repair (lmo0132). To further explore L. monocytogenes' stress response, we analyzed the whole proteomes of two different L. monocytogenes 1/2a strains: 268M "ATCC BAA-679TM" as the reference strain and 3178-CB-2018, a wild type from pork sausage. We identified 265 immunogenic proteins, with gene enrichment analysis confirming the activation of virulence and pathogenesis pathways under stress conditions. A subsequent study focused on a highly virulent strain (ST155) from a 2022 listeriosis outbreak in Italy, using a quantitative proteomic approach. This strain was cultivated under control conditions (C1) and conditions simulating the frankfurter matrix (C2). The analysis identified potential immunogenic targets, including lmo0723 proteins previously associated with the ST7 strain, and additional targets linked to flagellar assembly, surface interactions, host cell entry, and adhesion. Overall, understanding the adaptive mechanisms of L. monocytogenes can provide insights into new biomarkers for identifying strains in food products, thereby enhancing food safety and public health.

Chiaverini, A., Guidi, F., Torresi, M., Acciari, V. A., Centorotola, G., Cornacchia, A., Centorame, P., Marfoglia, C., Blasi, G., Di Domenico, M., Migliorati, G., Roussel, S., Pomilio, F., & Sevellec, Y. (2021). Phylogenetic Analysis and Genome-Wide Association Study Applied to an Italian Listeria monocytogenes Outbreak. Frontiers in microbiology, 12, 750065. https://doi.org/10.3389/fmicb.2021.750065

D'Onofrio, F., Visciano, P., Krasteva, I., Torresi, M., Tittarelli, M., Pomilio, F., Iannetti, L., Di Febo, T., Paparella, A., Schirone, M., & Luciani, M. (2022). Immunoproteome profiling of Listeria monocytogenes under mild acid and salt stress conditions. Proteomics, 22(18), e2200082. https://doi.org/10.1002/pmic.202200082