Investigation of the association between specific Campylobacter concisus virulence factors and host cell invasion

Campylobacter concisus is an emergent pathogen that is associated with gastroenteritis and Inflammatory Bowel Diseases (IBD). Previous studies have shown that C. concisus UNSWCD can attach to and invade human intestinal cells including the Caco-2 cells. A number of genes have been associated with the ability of C. concisus to invade host cells including the Campylobacter invasion antigen B (ciaB) a chromosomal gene associated with host cell invasion. The initial aim of this study was to develop a broth media that would support the growth of C. concisus UNSWCD and C. concisus ATCC-51561 in order to allow the determination of the effect of acid shock for 10 and 30 minutes on the survival of C. concisus. Additionally the ability of C. concisus UNSWCD and C. concisus ATCC-51561 to grow in media with a range of pH values was investigated. Further investigation of the effect of pH on the invasive potential of C. concisus UNSWCD was investigated using Caco2 cells. Furthermore studies were undertaken to determine the effect of knocking out the ciaB gene on the invasive potential of C. concisus UNSWCD. The results of this study showed that Brain Heart Infusion (BHI) and Mueller Hinton broth supplemented with 10% fetal bovine serum (FBS) were optimal media for the growth of C. concisus UNSWCD and C. concisus ATCC-51561respectively. Following a short exposure of C. concisus UNSWCD and C. concisus ATCC-51561 to pH 2 and pH 3, both strains showed extremely low percentage survival rates, these being 0.1% and 10%, respectively. The percentage survival rates at higher pH levels (pH 4-7) ranged from 70% to 100 % for both strains. Neither strain grew in media at pH values of 2, 3 and 4; however at pH 5, 6 and 7 growth of C. concisus UNSWCD and C. concisus ATCC-51561 reached a VI maximal concentration of 5.0 X 108 CFU/ml. The invasive potential of C. concisus UNSWCD grown at pH 4, 5, and 6 were extremely low, the relative percentage invasion levels being less than 0.01% while at pH 7 it was 0.05% and for the bacteria grown in HBA ...