However, here we describe the novel finding that some strains of H. pylori harbor multiple tandem copies of cagA. Among the strains that carry multiple cagA copies, PMSS1 was originally isolated from a patient with a duodenal ulcer and has recently been widely studied since it can persistently colonize mice; this provides an invaluable tool to study gastric disease development in an animal model (52). The gene discussed is S100A8; the disease is duodenal ulcer.