RESEARCH ARTICLE Summary. Forty nine Campylobacter jejuni isolates from cattle feces collected from Alberta feedlots and 50 clinical C. jejuni isolates from people in Alberta were tested for the presence of 14 genes encoding putative virulence factors by PCR. These included genes implicated in adherence and colonization (flaC, cadF, docC, racR, jlpA, peb1, and dnaJ), invasion (virB11, ciaB, pldA, and iamA) and protection against harsh conditions (htrA, cbrA, and sodB). The genes examined were widely distributed in both the cattle fecal isolates and the human isolates. Of the isolates tested, 67% contained all of the genes except virB11. The cadF gene was found in 100% of the isolates tested. The presence or absence of virulence-associated genes was not associated with the ability of the organism to colonize birds. All of the C. jejuni isolates used to challenge birds were able to colonize the animals regardless of virulence gene profile. While some diversity in the profile of the occurrence of vir- ulence-associated genes in C. jejuni exists, the distribution of these putative virulence-associated genes isolates from feedlot cattle feces and humans in Alberta was similar. In addition it was not possible to predict the ability of the selected isolates to colonize young chicks based on the presence of these genes coding for virulence determinants. [Int Microbiol 2011; 14(1):25-32] Keywords: Campylobacter jejuni · virulence genes · bacterial adherence · bacterial invasion · bacterial colonization Introduction Bacteria belonging to the genus Campylobacter are frequently isolated from people with gastrointestinal infections [3,22,40]. Campylobacter jejuni and Campylobacter coli are the two most common species isolated from human cases of campy- lobacteriosis [3,41], although C. jejuni is responsible for the majority of these infections [4]. The spectrum of disease observed in C. jejuni-infected individuals ranges from asymptomatic infection to severe enteritis, and may include fever, severe abdominal cramps and diarrhea with blood and mucus [2,10]. Campylobacter jejuni is also the infectious agent most frequently associated with the development of immunoreactive complications such as Guillain-Barré and Miller-Fisher syndromes [16], and recent evidence has revealed that C. jejuni infection may lead to the development of serological markers for celiac disease in people [43]. These complications enhance the significance of infection by this bacteria. INTERNATIONAL MICROBIOLOGY (2011) 14:25-32 DOI: 10.2436/20.1501.01.132 ISSN: 1139-6709 www.im.microbios.org *Corresponding author: B.J. Allan Vaccine and Infectious Disease Organization University of Saskatchewan 120 Veterinary Road Saskatoon, SK, S7N 5E3, Canada Tel. +1-3069661522. Fax +1-3069667478 E-mail: brenda.allan@usask.ca † Current address: Center for Food Safety, Department of Food Science, University of Arkansas, 2650 North Young Avenue, Fayetteville, AR 72704, USA Debabrata Biswas, 1† Sherry J. Hannon, 2 Hugh G. G. Townsend, 1 Andrew Potter, 1 Brenda J. Allan 1 * 1 Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, Canada. 2 Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada Received 18 February 2011 · Accepted 30 March 2011 Genes coding for virulence determinants of Campylobacter jejuni in human clinical and cattle isolates from Alberta, Canada, and their potential role in colonization of poultry