H. pylori clinical isolates have diverse babAB genotype distributions over different topographic sites of stomach with correlation to clinical disease outcomes

Abstract

Background: Intragenomic recombination between babA and babB mediates antigenic variations and may help H. pylori colonization. This study determined whether variable genotypes of babA and babB correlate to different clinical disease outcomes, and can distribute over the different gastric niches.

Results: This study enrolled 92 clinical strains (45 from peptic ulcer, 27 from gastritis, and 20 from gastric cancer) to detect whether the babA and babB are at locus A or B by PCR reactions using the primers designed from the upstream and variable region of the babA and babB genes. Four genotypes of babA and babB (A B, AB B, A AB, AB AB) were found. The distribution of the 4 genotypes in 92 clinical strains was significantly different among patients with different gastric diseases (p < 0.05). The isolates from gastric cancer patients had a higher rate of AB AB genotype than those from non-cancer patients (40.0% vs. 9.7%, p < 0.05). The AB AB genotype was associated with a higher intensity of intestinal metaplasia (p < 0.05), but did not correlate with a higher inflammation and colonization density in gastric histology (p > 0.05). Besides, the study enrolled 19 patients to verify whether variable genotypes of babAB existed in the different gastric niches. Among the patients infected with more than one babAB genotypes over antrum and corpus, there were higher rate of genotypes as A B or AB AB in isolates from antrum than in those from corpus (75.0 % vs. 16.7%, p < 0.05).

Conclusions: The H. pylori isolate with the AB AB genotype correlates with an increased gastric cancer risk, and colonize in an antrum predominant manner.

Figure 1

PCR banding patterns of babAB genotypes. (A) Primer pairs used for gene detection at locus A and B. The forward primers, HypDF1 and S18F1, located in the upstream region of babA or babB, are paired with BabAR1 or BabBR1 primers to determine whether the gene at locus A and B is babA or babB. (B) PCR banding patterns of genotype A B, AB B, A AB and AB AB. The AB B genotype showed two bacterial populations in the single-colony isolate, the dominant as babA and the minor as babB, at locus A. The strain with A AB genotype represented a dominant population of babB and a minor population of babA at locus B. The combination of AB B and A AB was defined as an AB AB genotype. Lane M1, a 100 bp molecular marker; lane M2, l HindIII marker. The size of PCR products at locus A and B was 2.1-2.6 kb and 1.0-1.5 kb, respectively.

Figure 2

The babA sequences at locus A of the antrum and corpus isolates. Cardinal numbers indicate different patients’ isolates. A1-4 and C1-4 were single-colony isolate isolated from the antrum and the corpus, respectively. White highlighting indicates amino acids different from consensus.

Figure 3

babAat locus A dominantly determined BabA expression. (A) Effect of babA at locus B on the BabA expression.The isolate (19C3) had babA at locus A and in-frame CT repeats of babA at locus B, which were compared with the isolate only having babA at locus A (19C1). The presence of babA at locus A and B was in the isolates 26A1, A4, C2 and C3, but C2 had an out of frame babA at locus B. (B) Effect of mixed genotype at locus A on the BabA expression. The isolates from one patient (no. 14) had a mixed genotype at locus A (14C2 and C3), which was compared with those with babA only at locus A (14A2 and A4). (C) Comparison of BabA between AB AB and A B genotypes. Hsp60 was as an internal control.