Objective  To explore the pathogenicity of Campylobacter jejuni (CJ) O∶19 strain after deletion of neuB1.   Methods  The mutant of CJ O∶19 by deleting neuB1

which LPS is deficient in sialic acid

was compared with the homologous wild strain by assaying their sensitivity to bactericidal activity

motility and autoagglutination of 10% normal human serum (NHS).   Results  The sensitivity of the mutant strain to bactericidal activity of serum was superior to that of the wild strain. The survival rate of the mutant strain was (20.6±7.4)% and (9.6±3.6)% after incubation with 10% NHS for 15 min and 60 min

that of wild strain was (36.9±5.9)% and (15.5±4.3)% respectively. The wild and mutant strains showed no significant difference in sensitivity to motility and autoagglutination of NHS.   Conclusion  The mutant strain possesses remarkable pathogenicity so that an inactivated vaccine from the mutant strain should be first considered.