Amoebae as Hosts and Vectors for Spread of Campylobacter jejuni
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Campylobacter jejuni is the leading bacterial cause of gastrointestinal diarrheal disease in humans worldwide. This zoonotic pathogen has a complex epidemiology due to its presence in many different host organisms. The overall aim of this thesis was to explore the role of amoebae of the genus Acanthamoeba as an intermediate host and vector for survival and dissemination of C. jejuni. Earlier studies have shown that C. jejuni can enter, survive and replicate within Acanthamoebae spp. In this thesis, I have shown that C. jejuni actively invades Acanthamoeba polyphaga. Once inside, C. jejuni could survive within the amoebae by avoiding localization to degradative lysosomes. We also found that A. polyphaga could protect C. jejuni in acid environments with pH levels far below the range in which the bacterium normally survives. Furthermore, low pH triggered C. jejuni motility and invasion of A. polyphaga. In an applied study I found that A. polyphaga also could increase the survival of C. jejuni in milk and juice both at room temperature and at +4ºC, but not during heating to recommended pasteurization temperatures. In the last study we found that forty environmental C. jejuni isolates with low bacterial concentrations could be successfully enriched using the Acanthamoeba-Campylobacter coculture (ACC) method. Molecular genetic analysis using multilocus sequence typing (MLST) and sequencing of the flaA gene, showed no genetic changes during coculture. The results of this thesis have increased our knowledge on the mechanisms behind C. jejuni invasion and intracellular survival in amoebae of the genus Acanthamoeba. By protecting C. jejuni from acid environments, Acanthamoebae could serve as important reservoirs for C. jejuni e.g. during acid sanitation of chicken stables and possibly as vectors during passage through the stomach of host animals. Furthermore, Acanthamoeba spp. could serve as a vehicle and reservoir introducing and protecting C. jejuni in beverages such as milk and juice. Validation of the ACC method suggests that it is robust and could be used even in outbreak investigations where genetic fingerprints are compared between isolates. In conclusion, Acanthamoeba spp. are good candidates for being natural hosts and vectors of C. jejuni.
Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. , 50 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1115
Amoebae-Bacteria interactions; Campylobacter jejuni; epidemiology; environmental stress; low pH; Acanthamoeba; coculture; intracellular trafficking; bacterial survival; beverages; ACC-method; enrichment; genetic stability; Trojan horse; reservoir; host; vector
Medical and Health Sciences
Research subject Infectious Diseases
IdentifiersURN: urn:nbn:se:uu:diva-255804ISBN: 978-91-554-9276-2OAI: oai:DiVA.org:uu-255804DiVA: diva2:842408
2015-09-10, A1:111a, Biomedicinskt Centrum, Husargatan 3, Ing C7:2, Uppsala, 09:00 (Swedish)
Lindmark, Hans, Docent
Ellström, Patrik, DocentOlsen, Björn, ProfessorAxelsson-Olsson, Diana, lektor
FunderSwedish Research Council Formas, 2220-8779-120, 221-2012-1442Medical Research Council of Southeast Sweden (FORSS)Swedish Research Council Formas, 2007-438Swedish Research Council for Environment, Agricultural Sciences and Spatial PlanningThe Crafoord Foundation
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