Conservation and microdiversity of the phospholipase A (pldA) gene of Helicobacter pylori infecting dyspeptics from different countries

Abstract

Phospholipase activity is important in bacterial pathogenicity and could contribute to the pathogenic role of Helicobacter pylori by degradation of the gastric mucus, and in maintaining long-term colonisation. Our aim was to determine the degree of variation in the phospholipase A gene (pldA) of H. pylori from different geographic locations, and to investigate links between pldA genotype and clinical disease severity, as well as with variation in cagA status and vacA genotypes. PCR-restriction fragment length polymorphism (RFLP) analysis with MboI and HaeIII was used to study 124 isolates from 10 countries that included the two genome-sequenced strains (26695 and J99), as well as Tx30a and NCTC 11637 (type strain). The 925-bp pldA fragment was amplified with a frequency of 90%. The presence of pldA was confirmed in the other strains using an alternative forward primer. Isolates were distinguished by PCR-RFLP analysis with 10 MboI and four HaeIII restriction patterns that combined to give 25 distinct pldA RFLP types. The pldA M2H2 strain genotype was most common (20%) in the UK but similar strains came from several other countries. Microdiversity was evident in pldA sequences of strains representing different RFLP types, and five M2H2 strains each had a distinct pldA sequence type. Intragenic variation was independent of gastric disease severity as well as strain cagA status and vacA genotype, with the exception of eight geographically diverse strains all with the pldA M4H3/cagA+/vacA s1m1 genotype predominantly from peptic ulcer patients. The study indicated a spectrum of genotypic variants and was supportive of a pldA function in H. pylori colonisation and persistence rather than in chronicity of infection. ß

Phospholipase A in Gram-negative bacteria and its role in pathogenesis

“…It was concluded that pldA is a conserved feature of the H. pylori genome, with isolates of the same PCR-RFLP genotype having a widespread geographical distribution. The study also supported the theory that the role for PLA activity in H. pylori is in colonization and persistence rather than in chronicity of infection (Xerry & Owen, 2001). …”

“…However, adherence to gastric epithelial cells in vitro does not imply that the mutant can successfully colonize in vivo. Xerry & Owen (2001), in a study to determine the degree of variation in the PLA gene in H. pylori isolates, found that the pldA gene is a highly conserved feature of the H. pylori genome irrespective of the geographical origin of the isolate. The study also investigated links between pldA genotype and clinical disease severity, as well as with variation in cagA status and vacA genotypes.…”

Characterization of a haemolytic phospholipase A2 activity in clinical isolates of Campylobacter concisus

“…Similar research with a H. pylori pldA mutant has been reported, suggesting that the H. pylori pldA phospholipase has a role in colonization of the gastric mucosa and possible tissue damage after colonization (Dorrell et al, 1999). Moreover, pldA gene has been related to colonization and persistence of H. pylori strains isolated from different geographical locations (Xerry & Owen, 2001). …”

“…Such enzymes include PLA in pathogens such as H. pylori (Dorrell et al, 1999;Tannaes et al, 2001;Xerry & Owen, 2001), Legionella species (Flieger et al, 2000), C. coli (Grant et al, 1997), Yersinia enterocolitica (Schmiel et al, 1998) and PLA 1 in Aeromonas species (Merino et al, 1999).…”

Cell-Associated Hemolysis Induced by Helicobacter pylori Is Mediated by Phospholipases with Mitogen-Activated Protein Kinase-Activating Properties

“…We also demonstrate that both H. pylori phospholipases analyzed mediate synergistic hemolysis in combination with the S. agalactiae CAMP factor. PldA1 is highly conserved among H. pylori strains, but variation in pldA1 sequences exists among strains from different geographic locales (35). Our current experiments also indicate that H. pylori PldD can activate ERK1/2 in AGS cells and thus represent a novel function of H. pylori phospholipases.…”