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Increase in acid tolerance of Campylobacter jejuni through coincubation with amoebae
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences. (infektionssjukdomar)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Infectious Diseases. (Infektionssjukdomar)
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2010 (English)In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 76, no 13, 4194-4200 p.Article in journal (Refereed) Published
Abstract [en]

Campylobacter jejuni is a recognized and common gastrointestinal pathogen in most parts of the world. Human infections are often food borne, and the bacterium is frequent among poultry and other food animals. However, much less is known about the epidemiology of C. jejuni in the environment and what mechanisms the bacterium depends on to tolerate low pH. The sensitive nature of C. jejuni stands in contrast to the fact that it is difficult to eradicate from poultry production, and even more contradictory is the fact that the bacterium is able to survive the acidic passage through the human stomach. Here we expand the knowledge on C. jejuni acid tolerance by looking at protozoa as a potential epidemiological pathway of infection. Our results showed that when C. jejuni cells were coincubated with Acanthamoeba polyphaga in acidified phosphate-buffered saline (PBS) or tap water, the bacteria could tolerate pHs far below those in their normal range, even surviving at pH 4 for 20 h and at pH 2 for 5 h. Interestingly, moderately acidic conditions (pH 4 and 5) were shown to trigger C. jejuni motility as well as to increase adhesion/internalization of bacteria into A. polyphaga. Taken together, the results suggest that protozoa may act as protective hosts against harsh conditions and might be a potential risk factor for C. jejuni infections. These findings may be important for our understanding of C. jejuni passage through the gastrointestinal tract and for hygiene practices used in poultry settings.

Place, publisher, year, edition, pages
2010. Vol. 76, no 13, 4194-4200 p.
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-134586DOI: 10.1128/AEM.01219-09ISI: 000279082800010PubMedID: 20453130OAI: oai:DiVA.org:uu-134586DiVA: diva2:372882
Available from: 2010-11-29 Created: 2010-11-29 Last updated: 2015-09-07Bibliographically approved
In thesis
1. Amoebae as Hosts and Vectors for Spread of Campylobacter jejuni
Open this publication in new window or tab >>Amoebae as Hosts and Vectors for Spread of Campylobacter jejuni
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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
National Category
Medical and Health Sciences
Research subject
Infectious Diseases
urn:nbn:se:uu:diva-255804 (URN)978-91-554-9276-2 (ISBN)
Public defence
2015-09-10, A1:111a, Biomedicinskt Centrum, Husargatan 3, Ing C7:2, Uppsala, 09:00 (Swedish)
Swedish 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
Available from: 2015-08-19 Created: 2015-06-18 Last updated: 2015-09-07

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