title: Shiga toxin-producing escherichia coli infections in Norway, 1992-2012: characterization of isolates and identification of risk factors for haemolytic uremic syndrome.
abstract: BACKGROUND
  Shiga toxin-producing E. coli (STEC) infection is associated with haemolytic uremic syndrome (HUS). Therefore Norway has implemented strict guidelines for prevention and control of STEC infection. However, only a subgroup of STEC leads to HUS. Thus, identification of determinants differentiating high risk STEC (HUS STEC) from low risk STEC (non-HUS STEC) is needed to enable implementation of graded infectious disease response.
  
  
  METHODS
  A national study of 333 STEC infections in Norway, including one STEC from each patient or outbreak over two decades (1992-2012), was conducted. Serotype, virulence profile, and genotype of each STEC were determined by phenotypic or PCR based methods. The association between microbiological properties and demographic and clinical data was assessed by univariable analyses and multiple logistic regression models.
  
  
  RESULTS
  From 1992 through 2012, an increased number of STEC cases including more domestically acquired infections were notified in Norway. O157 was the most frequent serogroup (33.6 %), although a decrease of this serogroup was seen over the last decade. All 25 HUS patients yielded STEC with stx2, eae, and ehxA. In a multiple logistic regression model, age ≤5 years (OR = 16.7) and stx2a (OR = 30.1) were independently related to increased risk of HUS. eae and hospitalization could not be modelled since all HUS patients showed these traits. The combination of low age (≤5 years) and the presence of stx2a, and eae gave a positive predictive value (PPV) for HUS of 67.5 % and a negative predictive value (NPV) of 99.0 %. SF O157:[H7] and O145:H?, although associated with HUS in the univariable analyses, were not independent risk factors. stx1 (OR = 0.1) was the sole factor independently associated with a reduced risk of HUS (NPV: 79.7 %); stx2c was not so.
  
  
  CONCLUSIONS
  Our results indicate that virulence gene profile and patients' age are the major determinants of HUS development.
authors.affiliation: Department of Foodborne Infections, The Norwegian Institute of Public Health, Oslo, Norway. lin.thorstensen.brandal@fhi.no.|Division of Infectious Disease Control, Department of Foodborne Infections, Norwegian Institute of Public Health, P.O. Box 4404, Nydalen, N-0403, Oslo, Norway. lin.thorstensen.brandal@fhi.no.
authors.forename: Lin T
authors.initials: LT
authors.lastname: Brandal
authors.affiliation: Department of Foodborne Infections, The Norwegian Institute of Public Health, Oslo, Norway. astrid.louise.wester@fhi.no.
authors.forename: Astrid L
authors.initials: AL
authors.lastname: Wester
authors.affiliation: Department of Infectious Disease Epidemiology, The Norwegian Institute of Public Health, Oslo, Norway. heidi.lange@fhi.no.
authors.forename: Heidi
authors.initials: H
authors.lastname: Lange
authors.affiliation: Department of Foodborne Infections, The Norwegian Institute of Public Health, Oslo, Norway. inger.lobersli@fhi.no.
authors.forename: Inger
authors.initials: I
authors.lastname: Løbersli
authors.affiliation: Gene Technology Section, Akershus University Hospital, Lørenskog, Norway. Bjorn-Arne.Lindstedt@ldh.no.
authors.forename: Bjørn-Arne
authors.initials: BA
authors.lastname: Lindstedt
authors.affiliation: Department of Infectious Disease Epidemiology, The Norwegian Institute of Public Health, Oslo, Norway. line.vold@fhi.no.
authors.forename: Line
authors.initials: L
authors.lastname: Vold
authors.affiliation: Division of Infectious Disease Control, The Norwegian Institute of Public Health, Oslo, Norway. georg.kapperud@fhi.no.|Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Oslo, Norway. georg.kapperud@fhi.no.
authors.forename: Georg
authors.initials: G
authors.lastname: Kapperud
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control; D029968:Escherichia coli Proteins / Q000235:genetics; D005260:Female; D005838:Genotype; D006463:Hemolytic-Uremic Syndrome / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D016133:Polymerase Chain Reaction / Q000379:methods; D012307:Risk Factors; D065288:Serogroup; D054323:Shiga-Toxigenic Escherichia coli / Q000302:isolation & purification*; D014774:Virulence / Q000235:genetics; D055815:Young Adult
chemical_list: D029968:Escherichia coli Proteins