Biotyping of Campylobacter pylori

Genomic DNA fingerprinting of clinical isolates of Helicobacter pylori by REP-PCR and restriction fragment end-labelling

Genetic diversity of 32 Helicobacter pylori strains isolated from patients with gastritis, gastric or duodenal ulcer, carcinoma, or lymphoma was determined by repetitive sequence element polymerase chain reaction (REP-PCR), and by the new typing method restriction fragment end-labelling (RFEL). Furthermore, these two methods were used to investigate a possible correlation between clinical symptoms and the genetic background of Helicobacter pylori. Both REP-PCR and RFEL revealed 31 different patterns for the 32 strains tested, but the pair of isolates with identical REP-PCR patterns was not the same as the pair of isolates with identical RFEL patterns. Computer-assisted analysis of the DNA fingerprints was used to determine similarity coefficients. This analysis revealed no clustering of disease-specific strains by any of the two methods.

Typing of Helicobacter pylori with monoclonal antibodies against Lewis antigens in lipopolysaccharide

Recently, it has been shown that the lipopolysaccharide (LPS) O antigen of Helicobacter pylori contains Lewis x (Lex), Lewis y (Ley), or both Lex and Ley antigens. We applied a serotyping method for H. pylori by an enzyme-linked immunosorbent assay with monoclonal antibodies (MAbs) specific for these antigens and the related fucosylated H type 1 (H1) antigen. The selected MAbs recognized the Lex and/or Ley structures in the LPS of H. pylori. The agreement between the results of biochemical compositional analysis and the serological data validated our serotyping system. A total of 152 strains from different geographic origins (The Netherlands, Canada, Poland, Italy, and People's Republic of China) were examined for typeability based on the presence of Lewis antigens. One hundred twenty-nine (84.9%) strains were typeable, and 12 different serotyping patterns were observed; 80.9% of the strains contained Lex and/or Le(y) antigens, and 18.4% reacted with the MAb against the related H1 antigen either alone or in combination with the Lex and/or Ley antigen. Our results show that the Lex and Ley antigens are frequently encountered in the LPS of H. pylori strains from various geographic origins. This typing method is an easy-to-perform technique, which can be used for strain differentiation in epidemiological studies of H. pylori infections.

Population genetic analysis of Helicobacter pylori by multilocus enzyme electrophoresis: extensive allelic diversity and recombinational population structure

Genetic diversity and relationships in 74 Helicobacter pylori isolates recovered from patients assigned to distinct clinical categories were estimated by examination of allelic variation in six genes encoding metabolic housekeeping enzymes by multilocus enzyme electrophoresis. Seventy-three distinct allele profiles, representing multilocus chromosomal genotypes, were identified. All six loci were highly polymorphic, with an average of 11.2 alleles per locus. The mean genetic diversity in the sample was 0.735, a value that exceeds the level of diversity recorded in virtually all bacterial species studied by multilocus enzyme electrophoresis. A high frequency of occurrence of null alleles (lack of enzyme activity) was identified and warrants further investigation at the molecular level. Lack of linkage disequilibrium (nonrandom association (of alleles over loci) indicates that horizontal transfer and recombination of metabolic enzyme genes have contributed to the generation of chromosomal diversity in H. pylori. In this sample of isolates, there was no statistically significant association of multilocus enzyme electrophoretic types or cluster of related chromosomal types and disease category.

Bacteriology of Helicobacter pylori

The discovery and first isolation of H. pylori in pure culture from gastric biopsies in 1982 provided the basis for a completely new area of microbiology. Since then, H. pylori has been an intensively pursued topic world-wide, and extensive data have been acquired on all aspects of its basic microbiology, both at the conventional phenotypic level and at the molecular level. H. pylori is a remarkable microorganism because of its ability to readily colonize a major proportion of human population worldwide and to persist successfully for long periods (probably decades) in a hostile environment. At the same time it interacts with the host immune system in such a way as to permit long-term survival. Blaser (1993) proposed a model in which both host and parasite adapt to down regulate inflammatory phenomena to promote survival. Urease production by H. pylori (an important factor in that process) is one of its most distinct features with a key role in its success as an infective agent. Another less obvious yet highly significant feature of H. pylori is the ability to achieve a high degree of interstrain diversity in genomic DNA nucleotide sequences, while maintaining overall genetic homology and phenotypic homogeneity amongst strains. The selective advantage this diversity provides the bacterium is not understood. A key objective of future microbiological studies should be to understand the population genetic structure of H. pylori. Most species of bacteria are clonal in natural population structure, yet all genomic data suggest the contrary is true for H. pylori. Furthermore, it is not clear if all strains of H. pylori are equally pathogenic, and that some subsets may possess additional pathogenicity factors that are responsible for the development of different disease pathologies. A phylogenetic framework of the genetic relationships of the clones within H. pylori would enable an examination of the total genetic diversity, with respect to ethnic or geographical population and the nature of the disease caused. A second aim would be to understand the mode of transmission of H. pylori from individual to individual. Although there is some evidence for either an oral-oral or a faecal-oral route, no reliable microbiological protocols exist for the isolation of H. pylori from non-gastric sites. There is therefore, considerable scope for the development of microbiological media and test methods for isolation from faeces and dental plaque, and possibly even food and environmental sources. To conclude, the availability of new information on the above aspects would greatly facilitate the monitoring of therapy; would enable more accurate epidemiological studies on the age of acquisition and spread of H. pylori infection; and would provide a basis for future prevention of disease by identification of individuals at high risk of infection with a particular pathogenic strain type.

Rapid fingerprinting of Helicobacter pylori by polymerase chain reaction and restriction fragment length polymorphism analysis

A simple and reliable technique was developed for differentiating Helicobacter pylori strains by restriction fragment length polymorphism analysis of polymerase chain reaction (PCR)-amplified DNAs. Oligonucleotide primer pairs developed to the urease, 48-kDa stress protein (htrA), and 26-kDa antigen-encoding genes were used to amplify fragments of the appropriate size from crude boiled cell preparations. The PCR-amplified products were digested with Sau3A, HaeIII, MspI, AluI, MluI, HinfI, and XbaI restriction endonucleases. Restriction fragment length polymorphisms were particularly evident within the urease and htrA genes and were easily detected by Sau3A, HaeIII, MspI, and AluI restriction endonuclease analysis. Double digestion of these separately amplified products or restriction analysis of multiple PCR-amplified fragments was found to discriminate 17 of 17 (100%) H. pylori strains which had unique genomic DNA fingerprints. Results of an investigation of multiple isolate sets obtained from patients before and after therapy was consistent with the hypothesis that treatment failures were due to the persistence of the same strain but did not discount the possibility that the patients were reinfected with a strain shared by family members or close contacts. The results indicate that the PCR-restriction endonuclease analysis method can be applied directly to biopsy samples, has the potential to fingerprint H. pylori isolates rapidly, and may permit detailed epidemiological investigations on the transmission of this important pathogen.

Categorization of clinical isolates of Helicobacter pylori on the basis of restriction digest analyses of polymerase chain reaction-amplified ureC genes

Restriction endonuclease analyses of a 1.1-kb polymerase chain reaction-amplified portion of the ureC gene from Helicobacter pylori were used to group or to differentiate 21 clinical isolates. Isolates were placed into 4 groups after HindIII digestion alone, and placement was expanded into 15 groups after isolates were digested with AluI and PvuI.

Evaluation of fingerprinting methods for identification of Helicobacter pylori strains

Variation amongst strains of Helicobacter pylori was examined by 35S-methionine-labelled protein SDS-PAGE (Radio-PAGE), immunoblot and DNA fingerprinting techniques. These methods allowed discrimination amongst isolates and showed total correlation. Pig and baboon gastric Helicobacter pylori-like organisms were found to be very similar to Helicobacter pylori by both Radio-PAGE and immunoblotting, whereas a Helicobacter mustelae isolate was markedly different. The HindIII restriction endonuclease digest patterns of Helicobacter pylori DNA illustrated the considerable genomic variation of this organism. The Radio-PAGE and immunoblot typing methods both gave precise identification of Helicobacter pylori strains, but Radio-PAGE was found to give higher resolution and represents a standardised universally applicable fingerprinting method for Helicobacter pylori.

Macromolecular structure and aggregation states of Helicobacter pylori urease

Urease purified from Helicobacter pylori by differential ultracentrifugation and fast pressure liquid chromatography was composed of subunits with apparent molecular weights (MrS) of 66,000 and 30,000. Electron microscopy of this purified material demonstrated that it formed disc-shaped macromolecular aggregates that were approximately 13 nm in diameter and 3 nm thick. Images of both negatively stained and shadowed preparations indicated that the discs tended to stack to form pairs and then these pairs further aggregated to form four-disc stacks. This stacking of subunits explains the heterogeneity observed previously in the molecular weight of urease preparations. In some negatively stained preparations there were also some smaller (approximately 8-nm-diameter) annular units present, which may represent individual urease units or possibly an aggregate of one of the two subunits from which urease is constructed.

Molecular techniques for studying the epidemiology of infection by Helicobacter pylori

The efficacy of one-dimensional sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell protein patterns for fingerprinting isolates of Helicobacter pylori was assessed by means of computerized numerical analysis. Virtually all strains were found to have unique, stable, and reproducible protein profiles. The application of this technique to a collection of isolates from eight patients showed clearly that each harboured a distinct strain that was present before treatment and persisted after treatment. This suggests that relapse was due to recrudescence of the same strain rather than re-infection with a different strain. Minor differences in protein banding profiles within sets of isolates from the same patient were evident, and this was confirmed by means of both two-dimensional PAGE protein patterns and restriction endonuclease analysis of DNA on the same strains.

Helicobacter pylori and gastric acid output in peptic ulcer disease

Helicobacter pylori is associated with peptic ulcer, and a causal relationship has been postulated. We investigated the association between Helicobacter pylori and gastric acid output. Two hundred forty-one patients were studied: 173 with duodenal ulcer, 51 with gastric ulcer (41 corpus, 10 prepyloric), and 17 with combined gastric and duodenal ulcer. In 194 patients (80%), Helicobacter pylori could be demonstrated histologically from gastric antral biopsies. The presence or absence of Helicobacter pylori was not influenced by age, sex, or use of tobacco or analgesics. Patients with duodenal ulcer or combined gastric and duodenal ulcer had similar gastric acid outputs irrespective of the presence or absence of Helicobacter pylori. However, gastric ulcer patients with Helicobacter had higher basal and maximal acid outputs when compared to patients without Helicobacter (mean basal output: 4.1 mmol/hr vs 2.4, P less than 0.05; mean maximal output 19.5 mmol/hr vs. 14.4, P less than 0.05). Although Helicobacter pylori is associated with both gastric ulcer and duodenal ulcer, its significance may be different in the two diseases.

Use of DNA restriction endonuclease digest and ribosomal RNA gene probe patterns to fingerprint Helicobacter pylori and Helicobacter mustelae isolated from human and animal hosts

Variation amongst strains of Helicobacter pylori and Helicobacter mustelae was examined by DNA restriction endonuclease digestion and rRNA gene patterns generated using a non-radioactive probe. Chromosomal DNA was extracted from 30 cultures of H. pylori from human, Rhesus monkey and pig gastric mucosa, and from three H. mustelae isolates from ferret gastric mucosa. DNA fingerprinting with Hae III and Hind III showed H. mustelae was relatively homogeneous but revealed genomic heterogeneity within H. pylori with at least 18 different DNA patterns identifiable amongst the 30 isolates. Five sets of strains other than duplicates with matching DNA fingerprints were identified within H. pylori. The Peruvian isolates were the largest identical set and comprised eight isolates from four different patients with five consecutive isolates from one patient. The Rhesus monkey strains were a relatively homogeneous set as were several Australian human isolates. The study demonstrates that rRNA gene restriction patterns provide a simple but highly discriminatory electrophoretic fingerprint for H. pylori with potential for use as a novel epidemiological marker in addition to total DNA digest analysis.

Helicobacter pylori and gastritis in patients with peptic ulcer and non-ulcer dyspepsia: ethnic differences in Singapore

Peptic ulcer occurs with different frequencies in the three main racial groups in Singapore. This study aimed firstly to determine the prevalence of Helicobacter pylori in peptic ulcer and non-ulcer dyspepsia patients of the different races and secondly, to assess the relation between H pylori, histological gastritis, patient diagnosis, and race. Gastric antral biopsy specimens from 1502 patients undergoing gastroduodenoscopy were studied and 892 (59%) were positive for H pylori. H pylori was strongly associated with gastritis: 873 of 1197 (73%) patients with gastritis were positive compared with 19 of 305 (6%) without gastritis (p less than 0.0001). The prevalences of H pylori and gastritis were similar in peptic ulcer patients of different races. Malay patients with non-ulcer dyspepsia, however, were less likely to be positive for H pylori (10 of 46 (22%] or to have antral gastritis (17 of 46 (37%] than Chinese (292 of 605 (48%) were positive for H pylori and 421 of 605 (70%) had gastritis) and Indians (35 of 61 (57%) were H pylori positive and 42 of 61 (69%) had gastritis). Patients with duodenal ulcer were more likely to be positive for H pylori than those with non-ulcer dyspepsia, even when subjects with gastritis were considered separately. While our results do not help to explain the observed racial differences in peptic ulcer frequency it may be that the pathophysiology of non-ulcer dyspepsia is different in the different races in Singapore.