A Nosocomial Outbreak of Invasive Listeriosis in An Italian Hospital: Epidemiological and Genomic Features.

Valeria Russini,Tiziana Zottola,Riccardo Marrone,Stefano Bilei,Martina Spaziante,Giovanni Blanco,Teresa Bossù,Gina Di Giampietro,Paolo Fabietti,Anna Giovanna Fermani,Maria Laura De Marchis,Sergio Parrocchia,Roberta Parisella

doi:10.3390/pathogens10050591

Abstract

Listeria monocytogenes (L. monocytogenes) is a widespread opportunistic pathogen that causes the listeriosis foodborne disease. This bacterium has become a common contaminant of handled food, and a relevant public health issue. Here we describe a nosocomial outbreak of listeriosis caused by an ST451 strain of L. monocytogenes involving three cancer and one immunocompromised patients hospitalized in different units from the same hospital during September and October 2020. The epidemiological investigation was conducted using traditional microbiological methodology combined with a whole genome sequencing approach. The source of contamination was identified in the kitchen hospital, where a meat slicer used to prepare patients’ meals was tested positive to the same sequence type (ST) of L. monocytogenes. This is the first report of an outbreak of listeriosis caused by ST451 in Italy.

Highlights

The Gram-positive L. monocytogenes is a facultative intracellular bacterium responsible for the food-borne disease listeriosis [1,2]
Among the suspected foods that could be related to the transmission of L. monocytogenes or those possibly manipulated on the meat slicer, we identified fennels, chicken salad, mozzarella cheese, and turkey meat
Whereas a direct or indirect person-to-person transmission was suggested in some L. monocytogenes nosocomial outbreaks, especially among neonates [5,15,16], the majority of transmissions turned out to be linked to contaminated food products such as vegetables [17], sandwiches [18], dairy products such as pasteurized milk cheese [19], ice cream [20], or milkshakes [21], meat jelly [22], or other meat products [23]

Summary

Introduction

The Gram-positive L. monocytogenes is a facultative intracellular bacterium responsible for the food-borne disease listeriosis [1,2]. Nosocomial outbreaks of listeriosis have been reported, especially among newborns and immunocompromised patients [5,6,7]. L. monocytogenes species is highly heterogeneous: it can be divided into 13 serotypes [8] and four PCR serogroups [9] related to four main lineages [10]. These categories can be further subdivided into geographically and temporally widespread clones by sequencing a small number of housekeeping genes with multilocus sequence typing (MLST) [11]. The core genome MLST (cgMLST)based typing is one of the most helpful methods for identification of epidemiological clusters [12]

Methods

Results

Conclusion