Cell cycle arrest & apoptosis of epithelial cell line by cytolethal distending toxin positive Campylobacter jejuni.

Background & objectives: Campylobacter jejuni is the leading cause of gastroenteritis worldwide; cytolethal distending toxin (CDT) being an important virulence determinant. As its role in pathogenesis remains unclear, this study aims to investigate cell cycle arrest and apoptosis by CDT (+ve) and CDT (-ve) C. jejuni isolates on HeLa cells. Methods: Culture supernatants and lysates from 10 C. jejuni isolates [CDT (+ve) and CDT (-ve), five each] were incubated with HeLa cells. CDT activity on HeLa cells was confirmed by cell distension, cell cycle arrest by flowcytometry, and apoptosis by DNA fragmentation and flowcytometry. Results: Culture supernatant and lysate of only CDT (+ve) C. jejuni isolates produced cell distension. For CDT (+ve) and CDT (-ve) isolates, the cells at G2/M phase after 24, 48 and 72 h were 25.8 ± 3.79 per cent and 11.2 ± 0.58 per cent, 72.9 ± 2.44 and 14.3 ± 1.88 per cent, 93.5 ± 0.54 per cnet and 18.0 ± 1.80 per cent respectively (P<0.001). All CDT (+ve) isolates induced DNA fragmentation. Apoptosis induced by CDT (+ve) C. jejuni was significantly greater than CDT (-ve) (26.3 ± 3.49 % vs. 10.4 ± 1.01% at 24 h, 43.9 ± 2.40% vs. 17.6 ± 0.88% at 48 h, 68.4 ± 1.61% vs. 28.4 ± 1.62% at 72 h); (P<0.001). Interpretation & conclusion: The present study shows that CDT (+ve) C. jejuni contributes to the pathogenesis through epithelial cell G2/M phase arrest and apoptosis.

Effect of the complement system on the sensitivity of Campylobacter jejuni and Campylobacter coli to human blood serum

We determined the sensitivity of five strains Compylobacter jejuni and C. coli isolated from children with diarrhea and from chicken feces to normal human blood serum (undiluted and at concentrationss of 10, 30, 50 and 70 per cent), hypogmmaglobulinemic serum and a complemented-deficient serum. Both species were highly sensitive to the bactecidal activity of human serum, regardless of their source. The highest bactericidal activity was observed with pooled fresh normal serum, with bacterial survival rates inversely correlated to serum dilutions. Inactivated serum had the least bactericidal activity. When complement was partially restored to inactivated serum, lower survival rates were observed. The hypogammaglobulinemic-normal complement-containing serum had strong bactericidal activity whereas the normal immunoglobulin-containing but complement-feficient serum had little bactericidal activity. These results suggest that Campylobacter may be able to directly activate complement by the alternative pathway