Helicobacter pullorum as a cause of enterohepatic disease in poultry and humans

Starting approximately two decades ago, research about Helicobacter organisms has progressively gained importance. One of the enterohepatic Helicobacter species (EHS) was isolated from chickens and humans and assigned Helicobacter pullorum. Although the scientific community tagged this species as a potential emerging pathogen, little information about its actual significance was available at the beginning of this thesis. Indeed, one had to guess at the actual prevalence of H. pullorum in its host species and information about virulence factors was very scarce. This thesis starts with an introduction about the relevant literature on the EHS highlighting the need for additional research. The general aims, described in the chapter subsequent to the literature review, comprised the investigation of the occurrence of H. pullorum in poultry and human beings and the study of the interaction of H. pullorum with its animal host. The experimental research is divided into two main parts, chapters 1 and 2. Chapter 1 includes the prevalence of H. pullorum in humans and chickens and its in vitro susceptibility to different antimicrobial agents. In chapter 2, bacteria-host interactions are studied both in vitro and in vivo. In the first study of chapter 1, the actual occurrence of H. pullorum in broiler chickens was determined. The caeca, colon, jejunum and liver of 110 animals obtained from 11 different flocks, were tested for the presence of H. pullorum using a PCR method based on the 16S rRNA gene; positive samples were re-examined with a conventional isolation method. Therefore, samples were inoculated onto brain heart infusion (BHI) agar supplemented with 10 % horse blood and subsequently incubated in a microaerobic atmosphere at 37°C for minimum three days. The retrieved H. pullorum isolates were examined by amplified fragment length polymorphism (AFLP) fingerprinting for investigating genetic diversity and relatedness between strains. In the caecum and colon, the PCR reaction for H. pullorum gave positive results in 33.6 % and 31.8 % of the samples, respectively. In total, 10.9 % and 4.6 % of all jejunum and liver samples, respectively, were positive for H. pullorum DNA. Sixteen isolates from caecal samples of chickens from two different flocks were obtained. AFLP analysis showed that these isolates and four additional isolates previously obtained from another flock, clustered with respect to their origin. This indicates that H. pullorum colonization may occur with a single strain that disseminates throughout the flock. Isolates obtained from different host species or geographical sources, displayed a distinctive pattern. Because literature data illustrated that this Helicobacter species may also be present in human beings, the objective of the second study of chapter 1 was to determine the prevalence of H. pullorum both in patients with gastrointestinal disease and clinically healthy people. In this experiment, faecal material from 531 individuals with gastrointestinal disease and 100 clinically healthy persons was examined for the presence of H. pullorum by the same PCR method as used in the first study. Samples proving positive in PCR were selected for isolation purposes in a similar way to the aforementioned study. H. pullorum DNA was demonstrated in faeces from 4.3 % of patients with gastrointestinal disease, but also from 4.0 % of clinically healthy persons. We were furthermore able to isolate one strain from a patient suffering from diarrhoea. To complete this first chapter, the in vitro activity of 13 antimicrobial agents against 21 poultry and two human H