HP and gastric cancer: According to the overlap analysis of non-Hp urease-producing bacteria and non-Hp nitrate-reducing bacteria, Streptococcus accounted for the largest proportion in Hp-negative gastric cancer at the family level, while Streptococcus pseudopneumoniae, Streptococcus parasanguinis, and Streptococcus oralis accounted for a larger proportion at the species level (Sohn et al., 2017).