The emerging importance of Shiga toxin-producing Escherichia coli other than serogroup O157 in England

Abstract

Introduction. Shiga toxin-producing Escherichia coli (STEC) can cause severe disease and large outbreaks. In England, the incidence and clinical significance of STEC serogroups other than O157 (non-O157) is unknown due to a testing bias for detection of STEC O157. Since 2013, the implementation of PCR to detect all STEC serogroups by an increasing number of diagnostic laboratories has led to an increase in the detection of non-O157 STEC. Hypothesis/Gap statement. Due to a bias in testing methodologies to select for STEC serogroup O157 in frontline diagnostic laboratories in most countries, very little surveillance data have been previously generated on non-O157 STEC. Aim. Five years (2014–2018) of STEC national surveillance data were extracted and descriptive analysis undertaken to assess disease severity of non-O157 STEC strains. Methods. Data from 1 January 2014 to 31 December 2018 were extracted from the National Enhanced Surveillance System for STEC and analysed. Results. The implementation of Gastrointestinal Polymerase Chain Reaction (GI-PCR) has resulted in a four-fold increase in the detection of non-O157 STEC cases between 2014 and 2018. There were 2579 cases infected with 97 different non-O157 serogroups. The gender distribution was similar amongst STEC O157 and non-O157 STEC cases with 57 and 56 % of cases being female respectively, but a significantly higher proportion of cases (P <0.001) under 5 years of age was observed among STEC O157 (22 %) cases compared to non-O157 STEC (14 %). The most common non-O157 serogroups were O26 (16 %), O146 (11 %), O91 (10 %), O128 (7 %), O103 (5 %) and O117 (3 %). Overall, rates of bloody diarrhoea were highest in O26 (44 %) and O103 (48 %) cases and lowest in STEC O117 cases (17 %). Strains harbouring Shiga toxin stx1a caused the highest proportion of diarrhoea (93 %) and caused the same level of bloody diarrhoea as stx2a (39 %). However, stx2a caused the highest proportion of vomiting (46 %), hospitalisation (49 %) and considerably more HUS (29 %) than other stx profiles. Conclusion. The implementation of PCR targeting stx at diagnostic laboratories has shown that non-O157 STEC, most notably STEC O26, are an emerging risk to public health.

The epidemiology of Shiga toxin-producing Escherichia coli serogroup O157 in England, 2009–2019

“…A previous study during the same time period suggests that severity is associated with the presence of the Shiga toxin subtype Stx2a, which is hosted on a bacteriophage harboured by this PT [ 18 , 19 ]. Although the percentage of cases that developed HUS decreased, the percentage of cases reporting bloody diarrhoea and hospitalisation remained stable, contributing to a growing body of evidence that other factors such as possessing multiple subtypes of stx genes [ 19 ] or harbouring stx1a [ 20 ] may contribute to severity. Consequently, while the incidence of STEC O157 with PT21/28 has decreased, and with it the proportion of HUS cases, STEC O157 PT8 stx1+2 strains appear to maintain the proportion of cases reporting bloody diarrhoea or hospitalisation.…”

“…Although the risk to children developing STEC-HUS caused by STEC O157 may have decreased, hospitalisations in all age groups remain high compared to other common gastrointestinal pathogens [ 24 ]. Enhanced surveillance data can support detection of emerging strain types and novel sources and transmission routes [ 18 , 20 , 25 ]. Integration of epidemiological data with microbiological typing data is essential to understanding the changes in the burden of STEC infection, assessment of the risks to public health, and the prediction and mitigation of emerging threats.…”

Shiga toxin-producing Escherichia coli clonal complex 32, including serotype O145:H28, in the UK and Ireland

“…Seven clusters were geographically dispersed, and likely to be associated with foodborne transmission (clusters 4,5,8,12,13,15,17). Eleven of the 17 clusters were temporally related, with the duration of time between cases ranging from 3 to 35 days (Table 3).…”

“…STEC CCs have different genomic characteristics, including different virulence gene profiles, diverse animal reservoirs and/ or transmission routes and variable geographical distribution; for example, STEC O117:H7 has been associated with travellers' diarrhoea and sexual transmission [14][15][16][17]. To date, the majority of reports on STEC data from the UK Health Security Agency (UKHSA) have focused on analysing non-O157 STEC as one group [13]. However, the increasing incidence and variety observed in their microbiological and epidemiological features has highlighted the need to consider each serotype or CC independently.…”

“…Historically in the UK, public health surveillance systems focused on STEC serotype O157:H7, as this serotype was the causative agent of the outbreak of HUS when STEC first emerged as a threat to public health in the 1980s [11]. However, over the last decade we have seen a decrease in the incidence of STEC O157, belonging to clonal complex (CC) 11, [12] and an increase in STEC belonging to other serotypes or CCs [13].…”