C. Jensen

Virulence Factors for Hemolytic Uremic Syndrome, Denmark

We present an analysis of strain and patient factors associated with the development of bloody diarrhea and hemolytic uremic syndrome (HUS) among Shiga toxin-producing Escherichia coli (STEC) patients registered in Denmark in a 6-year period. Of 343 STEC patients, bloody diarrhea developed in 36.4% and HUS in 6.1%. In a multivariate logistic regression model, risk factors for bloody diarrhea were the eae and stx2 genes, O groups O157 and O103, and increasing age. Risk factors for HUS were presence of the stx2 (odds ratio [OR] 18.9) and eae (OR undefined) genes, being a child, and having bloody diarrhea. O group O157, although associated with HUS in a univariate analysis (OR 4.0), was not associated in the multivariate analysis (OR 1.1). This finding indicates that, rather than O group, the combined presence of the eae and stx2 genes is an important predictor of HUS.

Etiology of Diarrhea in Young Children in Denmark: a Case-Control Study

ABSTRACT Infectious gastroenteritis is one of the most common diseases in young children. To clarify the infectious etiology of diarrhea in Danish children less than 5 years of age, we conducted a 2-year prospective case-control study. Stools from 424 children with diarrhea and 870 asymptomatic age-matched controls were examined, and their parents were interviewed concerning symptoms. Rotavirus, adenovirus, and astrovirus were detected by enzyme-linked immunosorbent assay, and norovirus and sapovirus were detected by PCR. Salmonella, thermotolerant Campylobacter, Yersinia, Shigella, and Vibrio spp. were detected by standard methods. Shiga toxin-producing (STEC), attaching-and-effacing (A/EEC), enteropathogenic (EPEC), enterotoxigenic, enteroinvasive, and enteroaggregative Escherichia coli were detected by using colony hybridization with virulence gene probes and serotyping. Parasites were detected by microscopy. Overall, a potential pathogen was found in 54% of cases. More cases than controls were infected with rotavirus, Salmonella, norovirus, adenovirus, Campylobacter, sapovirus, STEC, classical EPEC, Yersinia, and Cryptosporidium strains, whereas A/EEC, although common, was not associated with illness. The single most important cause of diarrhea was rotavirus, which points toward the need for a childhood vaccine for this pathogen, but norovirus, adenovirus, and sapovirus were also major etiologies. Salmonella sp. was the most common bacterial pathogen, followed by Campylobacter, STEC, Yersinia, and classical EPEC strains. A/EEC not belonging to the classical EPEC serotypes was not associated with diarrhea, underscoring the importance of serotyping for the definition of EPEC.

Risk factors for diarrhea among children in an industrialized country.

Background: Risk factors for childhood diarrhea in industrialized countries are not well characterized, although diarrhea remains an important cause of morbidity. Methods: We conducted a case–control study of 422 cases and 866 controls over 22 months in Denmark. We selected cases among children under 5 years of age with diarrhea. Age-matched healthy controls were selected from the background population using a population register. Parents were interviewed about possible exposures and underlying conditions. In addition, stool samples from both cases and controls were analyzed for viruses, parasites, and bacteria. We analyzed risk factors for diarrhea in general and for diarrhea of a viral, bacterial, or “unknown” etiology using logistic regression. Results: The following factors were independently associated with an increased risk of diarrhea: recent foreign travel, contact with symptomatic persons (particularly in daycare centers), hospitalization, contact with a dog with diarrhea, private daycare, consumption of products containing formula milk, unemployment and low educational status of parents, and prior diagnosis of several types of atopic diseases. In a pathogenic-specific analysis of diarrhea of bacterial (73 patients), viral (88), or “unknown” (222) etiology, the major risk factor for viral diarrhea was contact with symptomatic persons. For bacterial diarrhea, foreign travel and socioeconomic factors were the main risk factors. Conclusions: Viral diarrhea appears to be transmitted predominantly from person to person, whereas bacterial diarrhea appears to be primarily foodborne. A substantial portion of the diarrheal episodes may be of noninfectious etiology. Limiting child-to-child transmission of disease in daycare centers may substantially reduce the disease burden.

VTEC O117:K1:H7 A new clonal group of E. coli associated with persistent diarrhoea in Danish travellers

20 patients were infected with a new group of verocytotoxin-producing E. coli (VTEC) strains of serotype O117:K1:H7 during a 5-y period. The main symptoms were persistent watery diarrhoea with abdominal cramps; 2 persons of the 20 were healthy carriers. The duration of gastrointestinal symptoms in patients was median 11 weeks with 80% being ill for more than 30 d. In 19 cases the infection was acquired during travel (Asia, Africa and Cuba), and 1 case was laboratory acquired. All strains were positive for the vtx1 gene and negative for the vtx2, the eae, the saa and the ehxA genes. 13 strains (65%) were resistant to 4 or more antimicrobial agents. By PFGE using the restriction enzyme XbaI, the strains were clonally related, but not identical. O117:K1:H7 is a clonal group of VTEC that should be considered in patients returning from Africa and Asia with long-lasting watery diarrhoea.

First general outbreak of verocytotoxin-producing Escherichia Coli O157 in Denmark

This report describes the first general outbreak of verocytotoxin-producing E. coli (VTEC) in Denmark. Twenty five patients, 18 children and seven adults, with culture-confirmed VTEC O157:H- infection and indistinguishable pulsed-field gel electrophoresis DNA profiles, were identified during a six month period from September 2003 to March 2004. The outbreak strain possessed the virulence genes: eae, vtx1 and vtx2c. All patients but one presented with diarrhoea; none developed haemolytic uraemic syndrome. The outbreak was restricted to Copenhagen and surrounding areas. A case-control study including 11 cases and 55 matched controls revealed an association between VTEC O157:H- infection and shopping in a specific supermarket chain in Copenhagen and surrounding area, matched odds ratio (OR): 8.7 (95% confidence interval (CI): 1.1-71). After exclusion of three assumed secondary cases, only consumption of a particular kind of organic milk from a small dairy was associated with disease OR: 8.7 (95% CI 1.6-48). Environmental and microbiological investigations at the suspected dairy did not confirm the presence of the outbreak strain, but the outbreak stopped once the dairy was closed and thoroughly cleaned.

Antimicrobial treatment of asymptomatic carriers of verocytotoxin-producing Escherichia coli: An empiric study

Antimicrobial treatment of acute infection caused by verocytotoxin toxin-producing Escherichia coli (VTEC) is controversial due to risk of inducing haemolytic uraemic syndrome. We review the treatment of 9 persons who experienced serious social problems due to prolonged, asymptomatic carriage of non-O157 VTEC. Eradication of VTEC was successful and without complications.

Diarrheagenic potential of Escherichia coli in children in a developed country.

Escherichia coli is an underestimated diarrheal pathogen in developed countries. This organism may cause gastroenteritis by many different mechanisms, and on the basis of this, diarrheagenic E. coli has been subdivided into different groups, of which the most important ones are Shiga-toxigenic E. coli, enteropathogenic E. coli (EPEC), other attaching and effacing E. coli (A/EEC), enteroaggregative E. coli (EAEC), enterotoxigenic E. coli, and enteroinvasive E. coli. The latter two are associated with travel to less developed countries. Shiga-toxigenic E. coli is a well-established pathogen, whereas the pathogenic role of EPEC, A/EEC, and EAEC is less well established. We read the paper by Pabst et al. in the June issue of the Journal of Clinical Microbiology (1) with great interest. The authors try to shed light on the role of diarrheagenic E. coli in Switzerland by using a case-control setup and molecular diagnostic methods for the identification of the different E. coli groups. However, the study has a couple of shortcomings that makes us wonder if all of the conclusions presented are correct. Firstly, the authors do not take into account the potential bias of the travel history of the patients when comparing cases and controls. Travel may be an important confounder because none of the controls reported traveling, whereas travel was quite common among the patients; i.e., if a pathogen is more common in travelers than in patients with domestically acquired cases, it will not be possible to ascertain the relative importance of travel if the patients are compared with a group of controls who have not traveled in a univariate analysis. A way of circumventing the problem would be to exclude the travel-associated cases from the analysis. In the case of EAEC, the number of patients who had traveled was 9 or 47%; the total number of diarrheal patients who had traveled was 31. It is thus possible to compare the occurrence of EAEC in patients and controls with no travel history: The prevalence in patients was 9 of 156, and that in controls was 3 of 137. This difference is not statistically significant (P 0.21; Fisher’s two-tailed exact test). Secondly, the authors did not find any difference in the prevalence of EPEC between cases and controls. This conclusion may be questioned too, because the EPEC definition used is based solely on detection of the intimin gene (eae). In the definition of EPEC, the serotype of the strains should also be taken into account (2). We performed a study similar to that of Pabst et al. and found a strong correlation between disease in infants less than 2 years of age and EPEC, defined as eaepositive strains belonging to the classical EPEC O groups, whereas other A/EEC showed no correlation to disease (B. Olesen, P. Schiellerup, M. Helms, J. Neimann, F. Scheutz, and P. Gerner-Smidt, Abstr. 12th Eur. Congr. Clin. Microbiol. Infect. Dis., abstr. P607, 2002). Classical EPEC is the most common bacterial cause of diarrhea in children less than 2 years old in Denmark. We wonder if Pabst et al. would have reached the same conclusion had they serotyped their eae-positive isolates.