<prompt> All are true regarding Helicobacter pylori except:Less prevalent in developing countriesToxicogenic strains usually causes ulcersUrea breath test is positiveGram negative organism  <response>: Ans. is a ie Less prevalent in developing countries Ref. Harrison 17e p 946 16e, p 886 15e p 962 963All the options can be easily understood as they have been frequently asked in previous year papers. Only option b needs some explanation.Virulence factors in H. Pylori are-Vacuolating cytotoxin Vac AGroup of genes termed the cag pathogenicity island cag PAIHow do them because ulcers is not exactly known but their association with ulcers is firmly established. Lets see the evidences from Harrison - Cytotoxic strains are more commonly associated from patients with peptic ulcer disease than from persons without ulcersThe cag PAI genes confer enhanced virulence on H. Pylori strains by inducing inflammatory cells to produce cytokines. Patients with peptic ulcers or gastric adenocarcinomas are more likely to have a cag A antibodies than patients without these conditions. 