PCR amplification of 12 representative H. pylori isolates from patients in China with primers 5g and DP5. Lanes: 1, H. pylori strain R-50 with the A2143G mutation (CLR resistant); 2 to 12, wild-type H. pylori strains; 13, CLR-resistant reference H. pylori strain 5883 (A2143G); 14, CLR-sensitive wild-type H. pylori strain 26695; M, DNA molecular size marker.