HELICOBACTER-PYLORI VIRULENCE FACTORS

Among people infected with Helicobacter pylori, the virulence of the i nfecting strain is a major determinant of who develops disease. Strain s producing vacuolating cytotoxin activity are more commonly isolated front people with peptic ulcers than without, The gene encoding the to xin, vacA, varies between strains, especially in its signal sequence a nd mid regions. vacA genotype influences cytotoxin activity and signal sequence type correlates closely with peptic ulceration. infection wi th strains possessing cagA (cytotoxin associated gene A) is more commo n among people with peptic ulceration or gastric adenocarcinoma than w ithout, cagA is a marker for the cag pathogenicity island, which inclu des genes necessary for the enhanced inflammation induced by pathogeni c strains. Serological detection of infection with cagA(+) strains is at present the best practical test for virulence. However, before a st rategy of screening and selective treatment can be considered, it is i mportant to assess whether cagA(-) strains are entirely non-pathogenic ,