After obtaining positive cultures from the biopsies, 6 isolated colonies from a single culture plate were examined for the genotypes using polymerase chain reaction (PCR) approach as described previously [29, 30, 32]. Briefly, the genomic DNA was extracted from the colonies by the sterile micropestle in guanidinium isothiocyanate, and the prepared DNA was dissolved in 10 mM Tris-HCl (pH 8.3). Two microliters of the eluted DNA was subjected to each PCR reaction. Twelve paired primers (Table 1) were then used to amplify specific DNA fragments. The PCR was performed under the following condition: 30 cycles at 94°C for 1 min, 50.9–63°C for 2 min, 72°C for 1 min, and final extension at 72°C for 5 min. Mixed infection was defined as distinct expression of cagA, cagE, cagT, cagM, and vacA s- or m-regions among the 6 isolates isolated from one host.