Multilocus sequence types of Finnish bovine Campylobacter jejuni isolates and their attribution to human infections

Caroline Pa De Haan,Marjaana Hakkinen,Marja-Liisa Hänninen,Rauni I Kivistö,Jukka Corander

doi:10.1186/1471-2180-10-200

Caroline Pa De Haan, Marjaana Hakkinen + Show 3 more

Open Access

https://doi.org/10.1186/1471-2180-10-200

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Abstract

BackgroundCampylobacter jejuni is the most common bacterial cause of human gastroenteritis worldwide. Due to the sporadic nature of infection, sources often remain unknown. Multilocus sequence typing (MLST) has been successfully applied to population genetics of Campylobacter jejuni and mathematical modelling can be applied to the sequence data. Here, we analysed the population structure of a total of 250 Finnish C. jejuni isolates from bovines, poultry meat and humans collected in 2003 using a combination of Bayesian clustering (BAPS software) and phylogenetic analysis.ResultsIn the first phase we analysed sequence types (STs) of 102 Finnish bovine C. jejuni isolates by MLST and found a high diversity totalling 50 STs of which nearly half were novel. In the second phase we included MLST data from domestic human isolates as well as poultry C. jejuni isolates from the same time period. Between the human and bovine isolates we found an overlap of 72.2%, while 69% of the human isolates were overlapping with the chicken isolates. In the BAPS analysis 44.3% of the human isolates were found in bovine-associated BAPS clusters and 45.4% of the human isolates were found in the poultry-associated BAPS cluster. BAPS reflected the phylogeny of our data very well.ConclusionsThese findings suggest that bovines and poultry were equally important as reservoirs for human C. jejuni infections in Finland in 2003. Our results differ from those obtained in other countries where poultry has been identified as the most important source for human infections. The low prevalence of C. jejuni in poultry flocks in Finland could explain the lower attribution of human infection to poultry. Of the human isolates 10.3% were found in clusters not associated with any host which warrants further investigation, with particular focus on waterborne transmission routes and companion animals.

Highlights

Campylobacter jejuni is the most common bacterial cause of human gastroenteritis worldwide
Data from domestic human isolates as well as poultry C. jejuni isolates from the same time period
Between the human and bovine isolates we found an overlap of 72.2%, while 69% of the human isolates were overlapping with the chicken isolates

Summary

Introduction

Campylobacter jejuni is the most common bacterial cause of human gastroenteritis worldwide. Due to the sporadic nature of infection, sources often remain unknown. European countries, including Finland, the number of laboratory confirmed C. jejuni infections doubled in the last decade [2]. Campylobacter outbreaks are relatively uncommon in industrialized countries, and most of the cases occur sporadically [1]. The sources of infection remain mostly unknown. Epidemiological studies in Department of Food Hygiene and Environmental Health, University of Helsinki, Agnes Sjöberginkatu, Helsinki, Finland different countries indicate that eating improperly cooked meat and handling chicken carcasses are important risk factors for acquiring the illness [1,4]. Other risk factors highlighted in epidemiological studies include contact with pets [5], drinking untreated water [4] and swimming in natural water sources [6]

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