Abstract
ObjectiveSince 1987 all fecal samples referred to the clinical microbiology laboratory of the UZ Brussel were screened for the presence of Shiga toxin-producing E. coli (STEC). In this study all STEC strains isolated over a period of 27 years (1987–2014) were reexamined to achieve deeper insight in the STEC infections in our patient population.MethodsA total of 606 STEC strains from 604 patients were subjected to molecular methods for shiga toxin (stx) subtyping, detection of additional virulence genes, typing of the O-serogroups, and phylogenetic relatedness assessment of STEC O157:H7/H-.ResultsSince the introduction of PCR in 1991 the annual positivity rates varied between 1.1% and 2.7%. The isolation rate of STEC O157:H7/H- remained stable over the years while the isolation rate of non-O157 serotypes increased, mainly since 2011. The majority of the patients were children. Uncomplicated- and bloody diarrhea were the most prevalent gastrointestinal manifestations (respectively 51.9% and 13.6%), 4.3% of the strains were related to the hemolytic uremic syndrome (HUS), and 30.2% of the patients showed none of these symptoms. The strains were very diverse; they belonged to 72 different O-serovars and all stx subtypes except stx1d and stx2g were identified. Out of the 23 stx2f-positives one was associated with HUS and one belonged to the E. albertii species. As seen in other studies, the frequency of strains of the O157:H7/H- serotype and strains carrying stx2a, eaeA and ehxA was higher in patients with HUS.ConclusionsThe characteristics and trends of STEC infection seen in our patient population are similar to those noted in other countries. STEC infections in our hospital are mainly sporadic, and a substantial portion of the patients were asymptomatic carriers. Human STEC Stx2f infection was less rare than previously assumed and we report the first Belgian STEC stx2f HUS case and stx2f positive E. albertii infection.
Highlights
Ever since the first description of an outbreak of hemorrhagic colitis (HC) associated with Shiga toxin-producing Escherichia coli (STEC) in the United States in 1983, STEC have been identified worldwide as an important cause of human disease, mostly foodborne [1]
The characteristics and trends of STEC infection seen in our patient population are similar to those noted in other countries
In addition of uncomplicated to severe bloody diarrhea, STEC infections can evolve into the development of the life-threatening hemolytic uremic syndrome (HUS) [2]
Summary
Ever since the first description of an outbreak of hemorrhagic colitis (HC) associated with Shiga toxin-producing Escherichia coli (STEC) in the United States in 1983, STEC have been identified worldwide as an important cause of human disease, mostly foodborne [1]. In the spring of 2011 a very large and severe outbreak of HUS was caused by a rare hybrid Stx-producing enteroaggregative E. coli (Agg-STEC) of serotype O104:H4 underlining the possible danger of seemingly innocent STEC non-O157 serotypes. These strains carried genes involved in enteroaggregative adherence to enterocytes, including aaiC and aggR, as well as the stx gene [9]
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