CagL polymorphisms D58/K59 are predominant in strains isolated from Mexican patients with chronic gastritis.

Background: is a Gram-negative bacterium that colonizes the gastric mucosa in humans. One of the main virulence factors of is the pathogenicity island (PAI), which encodes a type 4-secretion system (T4SS) and the cytotoxin CagA. Translocation of CagA through the T4SS triggers host-signaling pathways. One of the T4SS proteins is CagL, which is necessary for CagA translocation. CagL is a 26-kDa protein that contains a hypervariable motif, which spans residues 58 to 62. Several polymorphisms in this region have been associated with different disease outcomes, e.g. in Mexico, N58 is associated with a higher risk of gastric cancer. The aim of this work is to analyze the sequence of the hypervariable motif (residues 58 to 62) of clinical isolates from Mexican patients with chronic gastritis, and to correlate these polymorphisms with the genotype.

Results: Of the 164 biopsies analyzed, only 30.5% (50/164) were positive for . Thirty-six of the 50 clinical isolates (72%) were positive, and 40 (80%) had the most virulent genotype (s1/m1). Of the positive strains, 94.4% were s1/m1. All the strains contained the gene. The most prevalent sequence in the polymorphic region (residues 58-62) was DKMGE (75.8%, 25/33), followed by NKMGQ and NEIGQ (6.1%, 2/33), and DEIGQ, NKMGE, DKIGE, and DKIGK (3%, 1/33). Regarding polymorphisms in positions 58 and 59, the most common were D58/K59 (81.8%, 27/33), followed by N58/K59 (9.1%, 3/33), and D58/E59 (3%, 1/33). Only two isolates (6.1%) contained residues N58/E59, which correspond to those found in strain ATCC 26695. 92.6% of the clinical isolates having polymorphism D58/K59 had the genotype s1/m1, considered to be the most virulent, while 7.4% had the genotypes s1/m2 and s2/m2.

Conclusions: In Mexican patients, CagL polymorphisms D58, K59, M60, E62, K122, and I134 are more common in patients with chronic gastritis.