From January 2011 to December 2014, 70 patients diagnosed with upper gastrointestinal diseases and H. pylori-positive status (9 with chronic gastritis, 21 with duodenal ulcer, 22 with gastric ulcer, and 18 with gastric carcinoma) were enrolled in this study. From each patient, the biopsies were taken from the antrum and body of stomach. We obtained 6 colonies from pooled isolates in one culture plate, for a total of 420 isolates, to study the H. pylori genes. cag-PAI status and the s-region or m-region of vacA in H. pylori were assessed by PCR using unique primers. Mixed infection was defined as distinct expression of cagA, cagE, cagT, cagM, and vacA s- or m-regions among the 6 isolates in one host. The PCR distribution of positive/negative results for individual genes was shown in Table 2. All the isolates from single infection (n = 300) and mixed infection (n = 120) were positive for cagA. There were no major differences of the gene distributions between the two groups.