Skip to main content
Login | Suomeksi | På svenska | In English

Browsing by Subject "Campylobacter jejuni"

Sort by: Order: Results:

  • Haittaeläimet maatilaympäristössä ja haittaeläimissä esiintyvät lämpökestoiset Campylobacter jejuni -bakteerit 
    Tikkanen, Jouni (2019)
    The Master's thesis was completed as part of the joint project (Haittaeläin) by the Finnish Food Authority (Ruokavirasto) and Natural Resources Institute Finland (Luke). In the project, rodents and shrews caught on farm premises were investigated for zoonotic bacterial pathogens. This thesis covers the thermophilic cam-pylobacter findings in the caught pests in autumn 2017.Rodents and shrews caught on farm premises were investigated for zoonotic bacterial pathogens. This thesis deals with the result of thermophilic campylobac-ters isolated from the pests in the autumn 2017. Thermophilic campylobacters (Campylobacter jejuni ja Cam-pylobacter coli) cause gastroenteritis called campylobacteriosis in humans, which is one of the most common cause for human gastroenteritis in the world. The literature review discusses the characteristics of thermo-philic campylobacters and their epidemiology, which focused on aspects of a public health and risk factors for campylobacteriosis and the major sources of campylobacters. Moreover, a current knowledge of campylo-bacters’ occurrence in rodents and shrews were summarized in the literature review. The presence of thermophilic campylobacters was investigated from 227 pooled samples, which comprised of a total of 442 intestinal samples collected from 12 different species. Three species (yellow-necked mouse, house mouse and bank vole) covered 81,3 % of all caught pests. The numbers of caught pests were not signif-icantly different between the farms when compared to a geographical position (south or north) or a type of farm (pig or cattle). The numbers of captured yellow-necked mice were significantly higher in farms in the south. Especially, yellow-necked mice and bank voles were detected to be campylobacter positive. Other campylobacter positive species were harvest mice, rats, field voles and southern voles. A total of 93 samples were detected as campylobacter positive and all of them were identified as C. jejuni. There was not signifi-cant difference on the numbers of campylobacter positive samples between the farms when compared the geographical position or the type of farm. 46 isolates of all 96 campylobacter positive samples were selected for a whole genome sequencing. After the raw read data was assembled, the contigs were analysed with MLST and cgMLST typing schemes by Ridom SeqSphere+. 41 isolates contained 14 new sequence types (STs). Instead, 5 isolates contained previously described STs: ST-1304, ST-2219 and ST-4791. According to MLST typing isolates obtained from voles differed from isolates from mice and rats. Moreover, cgMLST typing supported the conclusion. In the cgMLST typing scheme vole’s isolates were found to have more missing loci than isolates from mice or rats. Therefore, all isolates from voles, apart from two bank vole isolates belonging to ST-1304, contained less than 90 % loci compared to a reference genome. Furthermore, these same isolates were poorly identified in MALDI TOF analysis unlike other isolates. One interpretation to the difference between isolates could be that isolates from voles belong to a new C. jejuni subspecies.
  • Rate and molecular spectrum of spontaneous mutations and recombinations in Campylobacter jejuni 
    Yang, Xiaochang (2019)
    Campylobacter jejuni is one of the leading causes of human gastroenteritis. Globally, there has been an increasing trend in the incidence of campylobacteriosis. In the European Union, about 200,000 cases of campylobacteriosis are reported annually. C. jejuni 4031 was isolated from a water outbreak in Finland. This strain belongs to the ST-45 clonal complex. According to a previous study, this population has been stable over time and space and has showed low levels of genomic diversity compared with other populations. Therefore, it is meaningful to investigate the evolutionary mechanisms and ecological conditions behind these clones. The aim of this study was to investigate the evolution of C. jejuni 4031 by whole genome sequencing and bioinformatics tools, characterizing the rate and molecular spectrum of spontaneous mutation in these clones. In addition, the transformation pattern of C. jejuni 4031 was to be studied. This study composed of three independent experiments: mutation accumulation experiment, fluctuation analysis, and transformation cycle experiment, to investigate mutation and recombination events, respectively. The C. jejuni 4031 grown for 220 generations by single colony passaging method in NB2 agar plate and thereafter named C. jejuni 4031x12 was used as starting material for the studies. In total of 76 genomes from both mutation accumulation experiments and transformation cycle experiments, were subject to SNP calling. Results showed that C. jejuni 4031x12 could accumulate spontaneous mutations at a relatively low rate (4.1x10-10 mutation per generation per nucleotide) than conventional estimates, with mutational bias towards G:C>A:T transitions and coding regions. The fluctuation analysis proves that C. jejuni 4031x12 could obtain antibiotic resistance via transformation. However, no recombination events were observed from SNP results. In conclusion, C. jejuni 4031 has evolved at a much lower rate compared with prior knowledge. Results from fluctuation analysis and transformation cycle experiment suggest that there are no essential recombination barriers between C. jejuni 4031 and C. jejuni NCTC11168 but transformants may not have a competitive advantage over their non-transformed counterparts.

Yhteystiedot

HELSINGIN YLIOPISTO