Strategie di sorveglianza attiva e networking per il controllo delle infezioni da Listeria monocytogenes

Aim: the aim of this project was to activate an hospital and community surveillance system of listeriosis through epidemiological prospective and retrospective longitudinal study to describe prevalence of invasive infection and phenotypically and genotipically characteristics of the strains circulating in Northern Sardinia isolated from humans, foods and environment samples. Methods: L.monocytogenes strains isolated from 2013 to 2016 in food and environment samples and patients were analyzed for presence of virulence genes. The strains were characterized genotypically (PCR, PFGE, MLST) to define the spread of the pathogen and the relationships clonality between the strains of human and food origin. Furthermore, it was characterized the immune profile of patients with invasive disease vs health controls, through antigen specific stimulation of PBMC and cytofluorimetric analysis in blood samples. Results: Samples were positive for all 7 virulence-associated genes analyzed. 51,3%, 35,1% and 13,5% were identified serotype 4b, 1/2a and 1/2b, respectively. The PFGE showed the presence of 5 pulsetype, gruped in two major clusters (A,B,C-D,E) with 31,91% similarity index (Dice). This genetic variability was confirmed by MLST which identified 5 different STs (ST 1, ST 5, ST 8, ST 101, ST 121). Cytofluorimetric analysis showed the percentage of CD8 and CD4 T-cells significantly less in patient compared to a health control (19 ± 4 vs 4 ± 0.02, p> 0.0001); although, the CD8 cells of patient produced levels of cytokines (TNFα, IL-2) higher than health control. Conclusion: the results show that the active surveillance programs could be a crucial tool for assessing the incidence of listeriosis and describe the molecular characteristics of L.monocytogenes isolated. Also, the data obtained are an important tool for study how the immune profile can promote the development of invasive disease. The results obtained and the research protocols used are disclosed through a website.