Population genetics and molecular epidemiology of Campylobacter jejuni

• Main Author: Llarena, Ann-Katrin
• Other Authors: Skjerve, Eystein, University of Helsinki, Faculty of Veterinary Medicine, Department of Food Hygiene and Environmental Health, Helsingin yliopisto, eläinlääketieteellinen tiedekunta, Helsingfors universitet, veterinärmedicinska fakulteten, Hänninen, Marja-Liisa, Hakkinen, Marjaana
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Helsingin yliopisto 2015
• Subjects: environmental health; Arctic
• Online Access: http://hdl.handle.net/10138/158507

During the last 40 years, Campylobacter has emerged as the number one cause of human gasteroenteritis in the developed world, of which C. jejuni accounts for the majority of cases. This Campylobacter species has an extremely broad host-range, and has been isolated from arctic penguins to cattle. Broiler chickens has traditionally been considered as the reservoir of importance for public health, but evidence suggests that other source, both known and unknown, are relevant. To decrease the number of human infections, targeted control efforts to reduce C. jejuni exposure to humans are needed. Such control efforts relies on knowledge on the nature of C. jejuni in both established and candidate sources such as broilers and wild birds, respectively, and reliable methods to trace and attribute human infections. Therefore, this thesis evaluated the usefulness of three metabolic markers in source attribution, resolved a Campylobacter outbreak using whole-genome sequence and characterized the dynamics and epidemiology of C. jejuni in Finnish chickens and barnacle geese. First, the possible host association of three metabolic markers, gamma-glutamyl transpeptidase, and the genes of secretory L-asparaginase and fucose permease, was investigated by examining their distribution among isolates collected from a variety of reservoirs and human patients, and by assessing their association with C. jejuni lineages as expressed by multilocus sequence typing. According to our results, the presence and absence of these three traits were linked to the lineages, and no evidence for host association independently of population structure was found. Therefore, these metabolic markers were deemed unsuitable as the sole subtyping scheme in source attribution. Secondly, in an attempt to identify possible new sources for human campylobacteriosis, the character, dynamics, and epidemiology of C. jejuni in barnacle geese and broiler chickens were investigated by multilocus sequence typing and whole-genome sequencing. In line with other studies, ...