Abstract
In Portugal, listeriosis has been notifiable since April 2014, but there is no active surveillance programme for the disease. A retrospective study involving 25 national hospitals led to the detection of an outbreak that occurred between March 2009 and February 2012. The amount of time between the start of the outbreak and its detection was 16 months. Of the 30 cases of listeriosis reported, 27 were in the Lisbon and Vale do Tejo region. Two cases were maternal/neonatal infections and one resulted in fetal loss. The mean age of the non-maternal/neonatal cases was 59 years (standard deviation: 17); 13 cases were more than 65 years old. The case fatality rate was 36.7%. All cases were caused by molecular serogroup IVb isolates indistinguishable by pulsed-field gel electrophoresis and ribotype profiles. Collaborative investigations with the national health and food safety authorities identified cheese as the probable source of infection, traced to a processing plant. The magnitude of this outbreak, the first reported food-borne listeriosis outbreak in Portugal, highlights the importance of having an effective listeriosis surveillance system in place for early detection and resolution of outbreaks, as well as the need for a process for the prompt submission of Listeria monocytogenes isolates for routine laboratory typing.
Highlights
Listeria monocytogenes is an intracellular bacterial pathogen of humans and a variety of animal species
The incidence of listeriosis increased in several European countries between 2009 and 2013 and, was the most frequent cause of hospitalisation and death (15.6%) due to the consumption of contaminated food in Europe in 2013 [2]. This increase reinforces the need for each country to establish enhanced molecular surveillance of listeriosis for efficient outbreak detection, investigation and control, as carried out by PulseNet USA or the Centre National de Référence des Listeria, Institut Pasteur, Paris, for example [3,4]
Results demonstrated that the majority (59%) of the participating laboratories were able to produce a pulsed-field gel electrophoresis (PFGE) gel of sufficiently high quality and the average score for serotyping among the participants was 94% and 97% for traditional and multiplex PCR based methods, respectively; higher quality could be achieved through trouble-shooting assistance and training
Summary
Listeria monocytogenes is an intracellular bacterial pathogen of humans and a variety of animal species. The incidence of listeriosis increased in several European countries between 2009 and 2013 (such as Germany, the Netherlands, Spain and the United Kingdom [1,2]) and, was the most frequent cause of hospitalisation and death (15.6%) due to the consumption of contaminated food in Europe in 2013 [2]. This increase reinforces the need for each country to establish enhanced molecular surveillance of listeriosis for efficient outbreak detection, investigation and control, as carried out by PulseNet USA or the Centre National de Référence des Listeria, Institut Pasteur, Paris, for example [3,4]. Results demonstrated that the majority (59%) of the participating laboratories were able to produce a PFGE gel of sufficiently high quality and the average score for serotyping among the participants was 94% and 97% for traditional and multiplex PCR based methods, respectively; higher quality could be achieved through trouble-shooting assistance and training
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