SF6022 - Identification of Bacterial Components That Influence Colonization of Poultry by Campylobacter jejuni

Researcher:

Dr. Brenda Allan, Veterinary Infectious Disease Organization

Objectives:

Long term

• To increase food safety by the reduction of colonization of poultry by C. jejuni.
  

Specific

• To identify factors which contribute to the colonization of poultry by C. jejuni.
  
• To identify factors that are important in the spread of C. jejuni from one animal to another.

Expected Benefits:

• Investigation of the colonization of poultry by C. jejuni to determine what factors are required for efficient colonization will provide information that will be essential in developing an effective vaccination program for the control of colonization of poultry by C. jejuni.

Summary of Research Results:

Campylobacter jejuni is the leading cause of bacterial gastroenteritis in humans in North America. The handling and consumption of poultry has been identified as a major risk factor for infection of humans by C. jejuni. Chicks, at one-day of age, are not colonized by C. jejuni, but by two weeks of age it is possible to detect colonization of birds. At time of slaughter, between 30 and 100% of the flocks are colonized. During the slaughtering process C. jejuni may be spread to previously uncontaminated carcasses. Colonization of poultry produces no harmful effect in the birds. However, reduction of the level of colonization of poultry by C. jejuni has been identified as a priority to increase food safety and improve human health.

The overall objective of this research was to understand the mechanism of colonization of poultry by C. jejuni. We have done an extensive comparison of two closely related variants of C. jejuni. C. jejuni-V1 colonizes birds well while C. jejuni-V26 colonizes birds poorly. Both of these strains were derived from the same parent bacterial strain and do not differ in their genomic DNA composition. The two variants differ in the way the DNA is expressed. These differences were observed by a number of analyses, including transcriptional analysis, proteomic analysis, motility measurements, tissue culture assays, electron microscopy and chick colonization studies. The most obvious difference between the two variants is the lack of polar flagella on the variant that colonizes poultry poorly. This, however, is not the only difference observed.

We have also studied the role of surface structures on colonization of poultry. Because capsular polysaccharides are the outermost structure on the bacterial cell, they play an important role in the interaction of bacteria, host and environment. In this study we have shown that the presence of an intact capsule plays an important role in the colonization of poultry. Mutations that result in the loss of the capsule also result in the loss of the ability to colonize birds. C. jejuni lipooligosaccharides (LOS) have received much attention due to their potential role in virulence in humans. We have demonstrated that they are also important in the colonization of poultry.

Glycosylation of proteins was once considered to be of little importance in bacteria. We have determined that in C. jejuni N-linked glycoyslation of proteins plays an important role in colonization of poultry.

This work provides information that will be essential in development of an effective vaccination program or other intervention program for the control of colonization of poultry by C. jejuni. Reduction of colonization of poultry will result in a decrease in risk of the occurrence of gastroenteritis and long term sequelae caused by C. jejuni in humans and to enhance food and water safety.