Listeriosis outbreak likely due to contaminated liver pâté consumed in a tavern, Austria, December 2018

Abstract

In late December 2018, an outbreak of listeriosis occurred after a group of 32 individuals celebrated in a tavern in Styria, Austria; traditional Austrian food (e.g. meat, meat products and cheese) was served. After the celebration, 11 individuals developed gastrointestinal symptoms, including one case with severe sepsis. Cases had consumed mixed platters with several meat products and pâtés originating from a local production facility (company X). Human, food and environmental samples taken from the tavern and company X were tested for L. monocytogenes. Whole genome sequence-based typing detected a novel L. monocytogenes strain of serotype IVb, sequence type 4 and CT7652 in 15 samples; 12 human, two food and one environmental sample from company X with an allelic difference of 0 to 1. Active case finding identified two further cases who had not visited the tavern but tested positive for the outbreak strain. In total, 13 cases (seven females and six males; age range: 4-84 years) were identified. Liver pâté produced by company X was identified as the likely source of the outbreak. Control measures were implemented and since the end of December 2018, no more cases were detected.

Keywords: Austria; Listeria monocytogenes; liver pâté; outbreak; whole genome sequencing.

Figure 1

Minimum spanning tree representing the genetic relatedness among the 17 sequenced isolates based on their core genome, Styria, Austria, 2018

Figure 2

Cases of listeriosis, by date of symptom onset, Styria, Austria, 2018 (n = 13)

Figure 3

Map showing the geographical location of confirmed cases, the tavern and company X, Styria, Austria, 2018