Bacteriuria and antibiotic susceptibility of Escherichia coli among migrants: a register-based study.

Background and relevance

Migrants constitute an increasing part of the population in European countries including Denmark. On November 1st 2017 immigrants constitute 10% of the Danish population of whom 58% come from non-Western countries1. Disease patterns vary with different groups of migrants as they are determined by risk factors associated with migration processes, cultural traditions, and socioeconomic status2.

Studies have shown variations in infectious disease patterns3 and a higher mortality from infectious diseases among migrants compared to the local born population4,5. Further,  Gopal et al. showed that in a multi-ethnic population in London patients of South Asian ethnicity were significantly more likely to have extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBLE) bacteriuria than people of white ethnic background6. Apart from this, studies addressing resistance patterns in bacteriuria are scarce. Yet, knowledge on resistance patterns in bacteriuria in migrants could help identify risk groups and may aid in choice of empirical antibiotics. Therefore, we wish to address this gap in the literature and study the differences in distribution of urine isolates and the resistance patterns of the predominant bacteria in urine, E. coli, in migrants and Danish born individuals.

Hypothesis and research question

Reflecting the scarce literature, we hypothesize that the distribution of urine isolates overall is the same in the two groups and that migrants have a higher occurrence of resistant E. coli urine isolates.

The project sets out to investigate the following research question:

  • Are there differences in types of causal infectious agents in bacteriuria in migrants compared to Danish-born individuals?
  • What are the resistance of coli to antimicrobial agents in migrants compared to Danish-born individuals?

Methods and Population


Our study population consists of migrants from the Migrant Cohort with a positive urine sample in the ADBact database and a comparison group of Danish-born individuals of Danish-born parents with a positive urine sample in the ADBact database.

The Migrant Cohort is composed of all migrants who obtained residence permits (both temporary and permanent) in Denmark as refugees or through family reunification between January 1, 1993 and December 31, 2015.

Identification of outcome: bacteriuria

Urine samples from January 1, 2000 to December 31, 2015 at Hvidovre Clinical Microbiology Department are extracted from the laboratory system ADBact. The ADBact database covers several hospitals in the Capital Region, Denmark. Inclusion criteria for bacteriuria are positive urine samples. Exclusion criteria are urine samples with negative, no or missing isolate analysis, and urine samples identified as contaminated.

Determinants and confounders

The population will be divided according to migrant status (i.e. refugees and family reunified immigrants). Thus migrant status are determinants in the study.

We will adjust for SES and comorbidity. Through data linkage to socioeconomic registries at Statistics Denmark we will account for the effect of SES. Through data from the Danish National Patient Registry on any previous hospital diagnosis with a chronic disease we will adjust for comorbidity based on the Charlson Comorbidity Index.


We will examine the differences in types of causal infectious agents and the resistance of E. coli to antimicrobial agents and adjust for SES and comorbidity by performing logistic regression multivariate analysis. Statistical analyses are performed using SAS statistical software.


The study will be carried out by stud. med. Louise Sloth during a 1-year scholarship at Section of Immigrant Medicine, Department of Infectious Diseases, Copenhagen University Hospital, Hvidovre Hospital (HVH). Louise will be supervised by PhD student Rikke Thoft Nielsen, Department of Clinical Microbiology, HVH and Research Centre for Migration, Ethnicity and Health, University of Copenhagen, and lector Marie Nørredam (principal supervisor), Section of Immigrant Medicine, Department of Infectious Diseases, HVH and Research Centre for Migration, Ethnicity and Health, University of Copenhagen, as well as Christian Østergaard Andersen, Department of Clinical Microbiology, HVH.

Ethical considerations

The project is approved by the Danish Data Protection Agency and we will seek approval from the local ethical committee, Hvidovre Hospital. All data will be made available and analyzed in an anonymous form by remote online access to the data set stored at Statistics Denmark.

  1. Statistics Denmark.
  2. Spallek, J., Zeeb, H. & Razum, O. What do we have to know from migrants’ past exposures to understand their health status? a life course approach. Emerg. Themes Epidemiol. 8, 6 (2011).
  3. Castelli, F. & Sulis, G. Migration and infectious diseases. Clin. Microbiol. Infect. 23, 283–289 (2017).
  4. Norredam, M., Olsbjerg, M., Petersen, J. H., Bygbjerg, I. & Krasnik, A. Mortality from infectious diseases among refugees and immigrants compared to native Danes: A historical prospective cohort study. Trop. Med. Int. Heal. 17, 223–230 (2012).
  5. Ikram, U. Z. et al. All-cause and cause-specific mortality of different migrant populations in Europe. Eur. J. Epidemiol. 31, 655–665 (2016).
  6. Gopal Rao, G., Batura, D., Batura, N. & Nielsen, P. B. Key demographic characteristics of patients with bacteriuria due to extended spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in a multiethnic community, in North West London. Infect. Dis. (London, England) 47, 719–24 (2015).