Campylobacter jejuni Colonization in Wild Birds: Results from an Infection Experiment

Campylobacter jejuni is a common cause of bacterial gastroenteritis in most parts of the world. The bacterium has a broad host range and has been isolated from many animals and environments. To investigate shedding patterns and putative effects on an avian host, we developed a colonization model in which a wild bird species, the European Robin Erithacus rubecula, was inoculated orally with C. jejuni from either a human patient or from another wild bird species, the Song Thrush Turdus philomelos. These two isolates were genetically distinct from each other and provoked very different host responses. The Song Thrush isolate colonized all challenged birds and colonization lasted 6.8 days on average. Birds infected with this isolate also showed a transient but significant decrease in body mass. The human isolate did not colonize the birds and could be detected only in the feces of the birds shortly after inoculation. European Robins infected with the wild bird isolate generated a specific antibody response to C. jejuni membrane proteins from the avian isolate, which also was cross-reactive to membrane proteins of the human isolate. In contrast, European Robins infected with the human isolate did not mount a significant response to bacterial membrane proteins from either of the two isolates. The difference in colonization ability could indicate host adaptations

The abundant free-living amoeba, Acanthamoeba polyphaga, increases the survival of Campylobacter jejuni in milk and orange juice

Background: Campylobacter jejuni is a common cause of human bacterial diarrhea in most parts of the world. Most C. jejuni infections are acquired from contaminated poultry, milk, and water. Due to health care costs and human suffering, it is important to identify all possible sources of infection. Unpasteurized milk has been associated with several outbreaks of C. jejuni infection. Campylobacter has been identified on fresh fruit, and other gastrointestinal pathogens such as Salmonella, E. coli O157:H7 and Cryptosporidium have been involved in fruit juice outbreaks. C. jejuni is sensitive to the acidic environment of fruit juice, but co-cultures with the amoeba, Acanthamoeba polyphaga, have previously been shown to protect C. jejuni at low pH. Methods: To study the influence of A. polyphaga on the survival of C. jejuni in milk and juice, the bacteria were incubated in the two products at room temperature and at 4°C with the following treatments: A) C. jejuni preincubated with A. polyphaga before the addition of product, B) C. jejuni mixed with A. polyphaga after the addition of product, and C) C. jejuni in product without A. polyphaga. Bacterial survival was assessed by colony counts on blood agar plates. Results: Co-culture with A. polyphaga prolonged the C. jejuni survival both in milk and juice. The effect of co-culture was most pronounced in juice stored at room temperature. On the other hand, A. polyphaga did not have any effect on C. jejuni survival during pasteurization of milk or orange juice, indicating that this is a good method for eliminating C. jejuni in these products. Conclusion: Amoebae-associated C. jejuni in milk and juice might cause C. jejuni infections

Data from: Marked host specificity and lack of phylogeographic population structure of Campylobacter jejuni in wild birds

Zoonotic pathogens often infect several animal species, and gene flow among populations infecting different host species may affect the biological traits of the pathogen including host specificity, transmissibility and virulence. The bacterium Campylobacter jejuni is a widespread zoonotic multihost pathogen, which frequently causes gastroenteritis in humans. Poultry products are important transmission vehicles to humans, but the bacterium is common in other domestic and wild animals, particularly birds, which are a potential infection source. Population genetic studies of C. jejuni have mainly investigated isolates from humans and domestic animals, so to assess C. jejuni population structure more broadly and investigate host adaptation, 928 wild bird isolates from Europe and Australia were genotyped by multilocus sequencing and compared to the genotypes recovered from 1366 domestic animal and human isolates. Campylobacter jejuni populations from different wild bird species were distinct from each other and from those from domestic animals and humans, and the host species of wild bird was the major determinant of C. jejuni genotype, while geographic origin was of little importance. By comparison, C. jejuni differentiation was restricted between more phylogenetically diverse farm animals, indicating that domesticated animals may represent a novel niche for C. jejuni and thereby driving the evolution of those bacteria as they exploit this niche. Human disease is dominated by isolates from this novel domesticated animal niche

Experimental setup and outcome.

a<p>samples for the control birds at day 19 were taken 5 h post-infection the same day as the challenge occurred.</p><p>Columns A–Y refer to individual birds. <i>Campylobacter jejuni</i> growth for each day is denoted as follows: R for rich growth (>100 cfu), M for median growth (11–100 cfu), and S for sparse growth (1–10 cfu). The challenge day is indicated with * for the human 00F4382 <i>C. jejuni</i> isolate and # for the Song Thrush 00-4:268 isolate.</p

Development of antibody responses over the course of the infection experiment.

<p>For each treatment group and sampling occasion, the mean (with 95% confidence interval) of the birds' antibody responses (mOD/min) to membrane proteins of the (A) human <i>C. jejuni</i> isolate 00F4382 and (B) the Song Thrush isolate 00-4:268 are given. The control birds are shown in blue, TR1 birds in green, and TR2 birds in yellow. Samples were taken at days 0, 6, 13, and 25 post-infection.</p

Body mass changes in European Robins <i>Erithacus rubecula</i> over the course of the infection experiment.

<p>Body mass is presented as the mean (±2 SE) of all individuals in each treatment group for each day over the course of the experiment. Challenge time points are marked with stars (*) for the human <i>C. jejuni</i> isolate 00F4382 and a bracket (#) for the Song Thrush isolate 00-4:268. Blood sampling time points are noted with hatched reference lines at days 0, 6, 13, and 25 post-infection.</p

Wild_bird_isolates_concatenated_alignment

A fasta-file alignment containing the concatenated MLST sequences from each wild bird C. jejuni isolate presented in the article