Molecular surveillance of Listeria monocytogenes strains isolated in Umbria and Marche (Italy) in 2018

Listeria monocytogenes (Lm) is a Gram-positive food-borne bacterium causing listeriosis in humans. Invasive listeriosis can occur in healthy people, but it affects predominantly immunocompromised individuals, elderly and young babies causing septicemia and meningitis. Moreover in pregnant women infections may lead to abortion, still birth, or fetal death. Although listeriosis is less frequent than other food-borne diseases, the fatality rate (13.8%) and hospitalization rates (98.6%) are high (EFSA 2018). Epidemiological surveillance programs rely on the continuous monitoring of circulating genotypes in space and time, enabling the rapid detection of common-source clusters and the implementation of control measures. For years, Pulsed-field gel electrophoresis (PFGE), has been considered the typing golden standard for epidemiological surveillance of Lm. Advances in high-throughput sequencing technologies have established Whole Genome Sequencing (WGS) based methods as powerful epidemiological typing tools with higher discriminatory power. Among these methods, the core genome MLST (cgMLST), MLST and SNP analyses were the most widely used for typing Lm in the public health sector. A joint ECDC-EFSA WGS database is being developed through the collaboration of Member States Competent Authorities for Lm. In Italy, the National Institute of Health (ISS) and the National Reference Laboratory for Lm (LNR-Lm) coordinate this activity. The Food Control Laboratory of IZSUM in Fermo, is responsible for the collection and the management of Lm strains isolated from human, food and environment in the regions of Umbria and Marche. This activity also includes the collection of epidemiological information about the isolates, the molecular typing of the strains and the elaboration of analytical results. The aim of this paper is to report the results coming from the activity carried out in the year 2018 by the IZSUM in collaboration with the LNR-Lm and the ISS