Abstract
The aim of this study was to determine the pathogenic markers associated with Campylobacter infection in humans. A total of 104 Campylobacter isolates obtained from poultry and humans were examined for the presence of nine virulence genes and their ability to adhere to, invade and produce cytotoxin were defined using HeLa cells. The diversity of the Campylobacter spp. isolates was studied based on sequencing of the SVR-region of flaA gene. Altogether 45 flaA-SVR alleles were identified among 104 Campylobacter isolates of poultry and human origin. All Campylobacter isolates possessed flaA, cadF and racR genes involved in adherence. Accordingly, all poultry and human isolates exhibited adherence towards HeLa cells at mean levels of 0.95% and 0.82% of starting viable inoculum, respectively. The genes involved in invasion (iam and pldA) and cytotoxin production (cdtA, cdtB and cdtC) were also widely distributed among the human and poultry Campylobacter isolates. Significantly higher invasiveness was observed for poultry isolates (mean level of 0.002% of starting bacterial inoculum) compared to human isolates (0.0005%). Interestingly the iam gene, associated with invasion, was more common in human (100%) than poultry (84%) isolates, and the poultry isolates lacking the iam gene showed a marked reduction in their ability to invade HeLa cells. Moreover, virB11 was present in 22% of the poultry and 70.4% of the human isolates. Strains lacking virB11 showed a slight reduction in invasion, however in the absence of iam even the poultry isolates containing virB11 were unable to invade HeLa cells. The mean cytotoxicity of Campylobacter isolates from poultry and human was 26.7% and 38.7%, respectively. Strains missing both the cdtB and cdtC genes were non-cytotoxic compared to strains containing all three cdtABC genes, which were the most cytotoxic among the C. jejuni and C. coli isolates from both sources. No cytotoxic effect was observed in only 4% of poultry and 5.6% of human isolates.
Highlights
The widespread occurrence of pathogens in the animal population contributes to their frequent presence in food and leads to foodborne diseases in human
Diversity of isolates flaA-short variable region (SVR) sequencing revealed a total of 28 different alleles among 50 Campylobacter isolates from poultry and 34 alleles among 54 isolates from humans (Fig. 1)
The results showed considerable and equal diversity both in Campylobacter spp. isolates obtained from poultry and human with Simpson's diversity index of 0.973 (CI 95% 0.960–0.986) and 0.979 (CI 95% 0.967–0.991), respectively
Summary
The widespread occurrence of pathogens in the animal population contributes to their frequent presence in food and leads to foodborne diseases in human. According to the scientific report of the European Food Safety Authority (EFSA, 2019), Campylobacter has been the most frequently isolated gastrointestinal bacterial pathogen in humans for the last 10 years. In four EU countries, including Poland, the isolation rate of this pathogen exceeded 50% in broilers. These data are in accordance with studies recently conducted in Poland (Wieczorek and Osek, 2015), Spain (Perez-Arnedo and Gonzalez-Fandos, 2019) and China (Zhang et al, 2018) describing poultry as a common reservoir of Campylobacter spp. Infected people exhibit a range of symptoms varying from mild watery
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