Abstract
An outbreak of gastroenteritis with 83 cases occurred at a conference venue in November 2017 in Halland County, Sweden. Stool samples from two venue visitors and a symptomatic secondary case attributed to household transmission were PCR-positive for the ipaH gene, a target found in both Shigella spp. and enteroinvasive Escherichia coli (EIEC). EIEC was isolated from stool samples and whole genome sequencing analysis confirmed EIEC O96:H19 to be the aetiological agent. A cohort study was conducted among venue attendees and employees and the findings implicated contaminated leafy greens as the vehicle of infection, however, no microbiological evidence could support the study results. Here, we report the investigation into the first recorded EIEC outbreak in Sweden and illustrate the challenges associated with the differential laboratory diagnostics of Shigella/EIEC in an outbreak setting.
Highlights
Enteroinvasive Escherichia coli (EIEC) and Shigella spp. are both Gram-negative bacteria causing diarrheal disease worldwide [1,2]
A few enteroinvasive Escherichia coli (EIEC) outbreaks have been reported in Europe, with the most recent ones having occurred in Italy in 2012 [15] and in the United Kingdom (UK) in 2014 [16]
The outbreak strain identified in these recent European outbreaks, EIEC O96:H19, is an emergent type of EIEC that has phenotypic characteristics more resembling those of noninvasive Escherichia coli (E. coli) than those described for Shigella [17]
Summary
Enteroinvasive Escherichia coli (EIEC) and Shigella spp. are both Gram-negative bacteria causing diarrheal disease worldwide [1,2]. In addition to a similar clinical picture, EIEC and Shigella share laboratory features that can make it difficult to distinguish between them in routine clinical laboratory practice Both pathogens are transmitted via the faecal-oral route and infections are frequently associated with consumption of contaminated food and water [7,8,9,10]. A few EIEC outbreaks have been reported in Europe, with the most recent ones having occurred in Italy in 2012 [15] and in the United Kingdom (UK) in 2014 [16] These outbreaks affected 109 cases and 157 probable cases, respectively, highlighting the fact that EIEC, like Shigella, has the capacity to cause large gastrointestinal disease outbreaks. These characteristics are suggested to contribute to improved survival abilities as well as the ability to better adapt to different ecological niches [17]
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