A highly specific and sensitive DNA probe derived from chromosomal DNA of Helicobacter pylori is useful for typing H. pylori isolates

Colonization of Helicobacter pylori in the oral cavity - an endless controversy?

Helicobacter pylori is associated with chronic gastritis, gastric or duodenal ulcers, and gastric cancer. Since the oral cavity is the entry port and the first component of the gastrointestinal system, the oral cavity has been discussed as a potential reservoir of H. pylori. Accordingly, a potential oral-oral transmission route of H. pylori raises the question concerning whether close contact such as kissing or sharing a meal can cause the transmission of H. pylori. Therefore, this topic has been investigated in many studies, applying different techniques for detection of H. pylori from oral samples, i.e. molecular techniques, immunological or biochemical methods and traditional culture techniques. While molecular, immunological or biochemical methods usually yield high detection rates, there is no definitive evidence that H. pylori has ever been isolated from the oral cavity. The specificity of those methods may be limited due to potential cross-reactivity, especially with H. pylori-like microorganisms such as Campylobacter spp. Furthermore, the influence of gastroesophageal reflux has not been investigated so far. This review aims to summarize and critically discuss previous studies investigating the potential colonization of H. pylori in the oral cavity and suggest novel research directions for targeting this critical research question.

The lipid A 1-phosphatase of Helicobacter pylori is required for resistance to the antimicrobial peptide polymyxin

Modification of the phosphate groups of lipid A with amine-containing substituents, such as phosphoethanolamine, reduces the overall net negative charge of gram-negative bacterial lipopolysaccharide, thereby lowering its affinity to cationic antimicrobial peptides. Modification of the 1 position of Helicobacter pylori lipid A is a two-step process involving the removal of the 1-phosphate group by a lipid A phosphatase, LpxEHP (Hp0021), followed by the addition of a phosphoethanolamine residue catalyzed by EptAHP (Hp0022). To demonstrate the importance of modifying the 1 position of H. pylori lipid A, we generated LpxEHP-deficient mutants in various H. pylori strains by insertion of a chloramphenicol resistance cassette into lpxEHP and examined the significance of LpxE with respect to cationic antimicrobial peptide resistance. Using both mass spectrometry analysis and an in vitro assay system, we showed that the loss of LpxEHP activity in various H. pylori strains resulted in the loss of modification of the 1 position of H. pylori lipid A, thus confirming the function of LpxEHP. Due to its unique lipid A structure, H. pylori is highly resistant to the antimicrobial peptide polymyxin (MIC > 250 microg/ml). However, disruption of lpxEHP in H. pylori results in a dramatic decrease in polymyxin resistance (MIC, 10 microg/ml). In conclusion, we have characterized the first gram-negative LpxE-deficient mutant and have shown the importance of modifying the 1 position of H. pylori lipid A for resistance to polymyxin.

Overexpression of TLR2 and TLR4 susceptibility to serum deprivation-induced apoptosis in CHO cells

We examined the effect of overexpression of TLR2 and TLR4 on apoptosis. TLR2 and TLR4 transfected CHO cells were subjected to serum deprivation for 0, 24, and 48 h. CHO cells served as control. The survival was 80.4% and 66.8% in CHO cells, 73.8% and 47.6% in TLR2/CHO, and 70.5% and 53.0% in TLR4/CHO, respectively. Flow cytometry examination suggested that apoptotic cells were 7.17% and 32.91% in control CHO cells, 29.0% and 64.6% in TLR2/CHO, and 41.4% and 64.6% in TLR4/CHO, respectively. The levels of FasL and caspase-8 activity in TLR2/CHO and TLR4/CHO cells were significantly higher than that of CHO cells. Transfection of dominant negative FADD into TLR2/CHO and TLR4/CHO cells significantly reduced apoptosis. Our results suggest that overexpression of TLR2 and TLR4 in CHO cells sensitizes the cells to serum deprivation-induced apoptosis and that the mechanisms are involved in the death receptor-mediated signaling pathway.

A novel 3-deoxy-D-manno-octulosonic acid (Kdo) hydrolase that removes the outer Kdo sugar of Helicobacter pylori lipopolysaccharide

The lipid A domain anchors lipopolysaccharide (LPS) to the outer membrane and is typically a disaccharide of glucosamine that is both acylated and phosphorylated. The core and O-antigen carbohydrate domains are linked to the lipid A moiety through the eight-carbon sugar 3-deoxy-D-manno-octulosonic acid known as Kdo. Helicobacter pylori LPS has been characterized as having a single Kdo residue attached to lipid A, predicting in vivo a monofunctional Kdo transferase (WaaA). However, using an in vitro assay system we demonstrate that H. pylori WaaA is a bifunctional enzyme transferring two Kdo sugars to the tetra-acylated lipid A precursor lipid IV(A). In the present work we report the discovery of a Kdo hydrolase in membranes of H. pylori capable of removing the outer Kdo sugar from Kdo2-lipid A. Enzymatic removal of the Kdo group was dependent upon prior removal of the 1-phosphate group from the lipid A domain, and mass spectrometric analysis of the reaction product confirmed the enzymatic removal of a single Kdo residue by the Kdo-trimming enzyme. This is the first characterization of a Kdo hydrolase involved in the modification of gram-negative bacterial LPS.

Expression of Helicobacter pylori vacuolating toxin in Escherichia coli

VacA is a secreted toxin that plays a role in Helicobacter pylori colonization of the stomach and that contributes to the pathogenesis of peptic ulcer disease. Studies of VacA structure and function have been hindered by the lack of an efficient system for expression and genetic manipulation of this toxin. In this study, we developed methodology for expression of a functionally active VacA toxin in Escherichia coli. We then used a high-throughput screen to analyze a library of mutant toxins with pentapeptide insertions and identified six mutants that lacked the capacity to induce vacuolation of HeLa cells. The capacity to analyze VacA in this heterologous-expression system should greatly facilitate efforts to elucidate the structure and function of this toxin.

A new method for rapid screening of bacterial species- or subspecies-specific DNA probes

A simple assay for the rapid screening of bacterial species- or subspecies-specific DNA probes for the random cloning method is presented, involving the use of genomic DNAs as probes and recombinant plasmid DNAs containing genomic DNA digested with HindIII as targets. The optimal amount of target DNAs and the concentration of digoxigenin-labeled genomic DNA probes were 20 ng and 100 ng ml(-1) (or 10 ng and 200 ng ml(-1)), respectively. The method was applied to the development of Fusobacterium nucleatum subspecies-specific probes. Our results showed that four out of 96 probes were F. nucleatum subspecies-specific, which was confirmed by Southern blot analysis. Our results indicate that the new method can be used for the rapid screening of species- or subspecies-specific probes.

Comparison of cytotoxin genotypes of Helicobacter pylori in stomach and saliva

We have previously reported a high prevalence of H. pylori DNA in saliva. In this study, the cytotoxin genotypes of H. pylori strains from both stomach and saliva were compared in 31 patients with gastritis and peptic ulcer. The cagA, vacA m1, vacA m2, and vacA s1 genotypes were analyzed by PCR. The 417 bp PCR products from three patients were also subjected to DNA sequencing analysis. There was 95% agreement between stomach H. pylori isolates and their corresponding saliva DNA in at least one cytotoxin genotype; 86% agreement with two cytotoxin genotypes; 59% agreement with three cytotoxin genotypes; and 27% agreement with all four cytotoxin genotypes studied. DNA sequencing from three patients showed 78.0%, 64.0%, and 66.9% homology of H. pylori from both sources, respectively. The data suggest that more than one H. pylori strain may exist in the stomach and saliva in the same patient.

Comparison of cytotoxin genotypes of Helicobacter pylori in stomach and saliva

We have previously reported a high prevalence of H. pylori DNA in saliva. In this study, the cytotoxin genotypes of H. pylori strains from both stomach and saliva were compared in 31 patients with gastritis and peptic ulcer. The cagA, vacA m1, vacA m2, and vacA s1 genotypes were analyzed by PCR. The 417 bp PCR products from three patients were also subjected to DNA sequencing analysis. There was 95% agreement between stomach H. pylori isolates and their corresponding saliva DNA in at least one cytotoxin genotype; 86% agreement with two cytotoxin genotypes; 59% agreement with three cytotoxin genotypes; and 27% agreement with all four cytotoxin genotypes studied. DNA sequencing from three patients showed 78.0%, 64.0%, and 66.9% homology of H. pylori from both sources, respectively. The data suggest that more than one H. pylori strain may exist in the stomach and saliva in the same patient.

Accurate diagnosis of Helicobacter pylori. Polymerase chain reaction tests

Although PCR has improved considerably the sensitivity of the diagnosis of H. pylori infection, many studies have not shown conclusively the full potential of PCR in clinical diagnosis. In daily clinical practice, PCR does not have to be performed to establish H. pylori infection. PCR is still classified primarily as a research technique in the Helicobacter field. PCR or similar technology will expand in the future when automation and commercialized kits are available to most laboratories. The development of a noninvasive PCR test may prove useful because it may lead ultimately to the determination of the source and route of transmission of this important pathogen.

Helicobacter pylori in the oral cavity: high prevalence and great DNA diversity

To test the hypothesis that Helicobacter pylori may be transmitted by the oral-oral route, we applied nested PCR and DNA sequencing to detect and analyze H. pylori DNA in the oral cavity of 20 adult patients undergoing endoscopy. Dental plaques of molars, premolars, and incisors and saliva were collected. Additional paraffin-embedded gastric biopsies were analyzed in four patients. Two sets of highly sensitive and specific primers, EHC-U/EHC-L and ET5-U/ET-5L directed to a 860-bp fragment of H. pylori DNA, were used in the nested PCR. Eight patients had an active infection in the stomach determined with the [13C]urea breath test and the other 12 were negative. Nested PCR showed that all 20 subjects (100%) were positive for H. pylori in the oral cavity. DNA sequencing demonstrated that all tested PCR products of the expected size from the oral samples have more than 97% identity with that from H. pylori type strain ATCC 43629. However, sequences differed in oral samples from different subjects as well as between different oral locations and gastric biopsies within the same individuals. In conclusion, the oral cavity may be a permanent reservoir for H. pylori and can harbor multiple H. pylori strains at the same time.

Identification of Campylobacter jejuni, C. coli, C. lari, C. upsaliensis, arcobacter butzleri, and A. butzleri-like species based on the glyA gene

Currently, the detection and identification of Campylobacter and Arcobacter species remains arduous, largely due to cross-species phenotypic similarities and a relatively narrow spectrum of biochemical reactivity. We have developed a PCR-hybridization strategy, wherein degenerate primers are used to amplify glyA fragments from samples, which are then subjected to species-specific oligodeoxyribonucleotide probe hybridizations, to identify and distinguish between Campylobacter jejuni, C. coli, C. lari, C. upsaliensis, Arcobacter butzleri, and an A. butzleri-like species. Evaluation of this strategy with genomic DNA from different type strains suggests that this approach is both specific and sensitive and thus may be applicable in a diagnostic assay to identify and differentiate these highly related species.

Quantitation of Helicobacter pylori in dental plaque samples by competitive polymerase chain reaction

AIM

To establish a competitive PCR (cPCR) assay for quantitation of H pylori organisms in dental plaque samples.

METHODS

The cPCR co-amplified target H pylori DNA and a known amount of internal standard template in the same tube with the same primers directed to 0.86 kb DNA of H pylori. The internal standard was a synthesised DNA bearing the same primer recognition sites at two ends and a non-homologous core sequence as the target DNA fragment. Quantitation was based on determination of the relative, not absolute, amounts of the differently sized and [32P]-dCTP labelled products derived from H pylori DNA and the competitive internal standard after gel electrophoresis separation.

RESULTS

A significant correlation between known amounts of H pylori added to dental plaque samples and the results of the cPCR was found, and a standard line was developed which allowed quantitation of H pylori in the plaque samples. cPCR was performed on supragingival plaque samples from 10 adult patients with H pylori infection in the stomach, and from five adults and six children without H pylori infection in the stomach. The ranges of H pylori numbers were 1-213 (median 25), 6-76 (10), and 4-94 (14) cells/mg of dental plaque in the three groups, respectively.

CONCLUSIONS

cPCR is useful for quantitation of H pylori in supragingival dental plaque samples; however, the number of the organisms in dental plaque samples seems very low.

Performance criteria of DNA fingerprinting methods for typing of Helicobacter pylori isolates: experimental results and meta-analysis

Typing systems are used to discriminate between isolates of Helicobacter pylori for epidemiological and clinical purposes. Discriminatory power and typeability are important performance criteria of typing systems. Discriminatory power refers to the ability to differentiate among unrelated isolates; it is quantitatively expressed by the discriminatory index (DI). Typeability refers to the ability of the method to provide an unambiguous result for each isolate analyzed; it is quantitatively expressed by the percentage of typeable isolates. We evaluated the discriminatory power and the typeability of the most currently used DNA fingerprinting methods for the typing of H. pylori isolates: ribotyping, PCR-based restriction fragment length polymorphism (PCR-RFLP) analysis, and random amplified polymorphism DNA (RAPD) analysis. Forty epidemiologically unrelated clinical isolates were selected to constitute a test population adapted to the evaluation of these performance criteria. A meta-analysis of typeability and discriminatory power was conducted retrospectively with raw data from published studies in which ribotyping, PCR-RFLP, RAPD, repetitive extragenic palindromic DNA sequence-based PCR (REP-PCR), or pulsed-field gel electrophoresis (PFGE) was used. Experimental results and the meta-analysis demonstrated the optimal typeability (100%) and the excellent discriminatory powers of PCR-based typing methods: RAPD analysis, DIs, 0.99 to 1; REP-PCR, DI, 0.99; and PCR-RFLP analysis, DIs, 0.70 to 0.97). Chromosome restriction-based typing methods (ribotyping and PFGE) are limited by a low typeability (12.5 to 75%) that strongly decreases their discriminatory powers: ribotyping, DI, 0.92; PFGE, DIs, 0.24 to 0.88. We do not recommend the use of ribotyping and PFGE for the typing of H. pylori isolates. We recommend the use of PCR-based methods.

Evaluation of two string tests for obtaining gastric juice for culture, nested-PCR detection, and combined single- and double-stranded conformational polymorphism discrimination of Helicobacter pylori

We have compared two gastric string tests for obtaining gastric juice for culture of Helicobacter pylori and for nested-PCR detection and PCR-based combined single- and double-stranded conformational polymorphism (SDSCP) discrimination of infecting strains. String test specimens were obtained from one seropositive volunteer for 13 consecutive weeks. The distal 10 cm of each string was suspended in 1 ml saline and quantitatively cultured. An additional nine volunteers with histories of upper-gastrointestinal complaints were given a string test for culture and nested-PCR assay. H. pylori isolates and/or gastric juice from each volunteer were extracted for DNA and analyzed by PCR-based SDSCP. Quantitative culture showed that the Entero-test was four times as sensitive as the Gastro-test but was more prone to contamination by oral flora. However, the two string tests are equally sensitive by PCR assays. Thus, the Gastro-test is more suitable for culture detection of H. pylori, since it is less prone to oral contamination and its shorter length is better tolerated. SDSCP analysis of H. pylori DNA from four PCR-positive volunteers without requiring culture showed four distinct profiles, indicating different infecting strains. SDSCP analysis of strains isolated before and after treatment of one volunteer had the same SDSCP profile, suggesting endogenous reinfection by the same strain.

Helicobacter pylori in dental plaque: a comparison of different PCR primer sets

This study was designed to compare different primer sets for PCR analysis of H. pylori in the same series of 40 dental plaque samples. Three pairs of primers, HPU1/HPU2, HP1/HP2, and EHC-U/EHC-L, directed to the urease A gene, 16S rRNA gene, or 860-bp DNA of H. pylori, respectively, were used. Our results demonstrate that EHC-L/EHC-U were more specific and sensitive for H. pylori added to saliva or dental plaque than HPU1/HPU2 and HP1/HP2. The detection rates for H. pylori DNA in dental plaque samples from randomly selected adult patients from the Dental Clinic of the University of Ulm were 26.5% (9/34) for HPU1/HPU2, 78.9% (30/38) for HP1/HP2, and 100% (40/40) for EHC-U/EHC-L (P < 0.001). Nested PCR using primers directed to the 860-bp DNA of H. pylori further confirmed the presence of H. pylori DNA (40/40) in all these samples. Our results indicate that primers EHC-U/EHC-L are to be recommended for PCR detection of H. pylori in the oral cavity.

Identification of H. pylori in saliva by a nested PCR assay derived from a newly cloned DNA probe

A novel probe was developed from genomic DNA of Helicobacter pylori ATCC type strain 43629. It hybridized with all 73 H. pylori clinical isolates tested but not with any of 183 non-H. pylori DNAs in dot blot hybridization. Typing tests revealed 41 different HaeIII-digestion patterns from 57 H. pylori strains tested. Based on the sequence of the probe, a nested PCR was developed that detected as little as 2 fg of H. pylori DNA or approximately equivalent to one cell. No PCR products were amplified from any of 21 non-H. pylori strains tested. Using this nested PCR, H. pylori DNA was detected in 33 of 45 (73%) saliva samples collected from patients with gastric H. pylori infection. These data suggest that the probe is useful for typing H. pylori and that the nested PCR is a valuable tool for detecting H. pylori DNA in saliva.

Differentiation of Helicobacter pylori strains directly from gastric biopsy specimens by PCR-based restriction fragment length polymorphism analysis without culture

Recent studies have shown the usefulness of PCR-based restriction fragment length polymorphism (RFLP) analysis for differentiating Helicobacter pylori strains isolated by culture. For this study, a PCR-based RFLP assay was developed for directly typing H. pylori strains from gastric biopsy specimens. Nineteen gastric biopsy specimens obtained from patients undergoing endoscopy for gastrointestinal complaints were cultured for isolation of H. pylori. Genomic DNA preparations from these gastric biopsy specimens and the corresponding H. pylori isolates were tested by our PCR-based RFLP assay. The 1,179-bp H. pylori DNA fragments amplified by the PCR assay were digested with the restriction enzymes HhaI, MboI, and AluI and analyzed by agarose gel electrophoresis. HhaI, MboI, and AluI digestion produced 11, 10, and 6 distinguishable digestion patterns, respectively, from the 19 H. pylori isolates tested and generated 13, 11, and 6 different patterns, respectively, from the 19 gastric biopsy specimens. The patterns from 13 of the 19 gastric biopsy specimens matched those of the H. pylori isolates from the corresponding patients. The patterns from the remaining six biopsy specimens appeared to represent infection by two strains of H. pylori; the pattern of one strain was identical to that of the isolate from the corresponding patient. By combining all the restriction enzyme digestion patterns obtained by using HhaI, MboI, and AluI, we observed 19 distinct RFLP patterns from the 19 specimens. The results suggest that the PCR-based RFLP analysis method may be useful as a primary technique to identify and distinguish H. pylori strains directly from gastric biopsy specimens without culture of the organisms.

A newly developed PCR assay of H. pylori in gastric biopsy, saliva, and feces. Evidence of high prevalence of H. pylori in saliva supports oral transmission

We have recently developed a new PCR assay for the detection of H. pylori. In this study, the polymerase chain reaction (PCR) assay was used to detect H. pylori in 88 gastric biopsy, 85 saliva, and 71 fecal specimens from 88 patients. H. pylori infection was confirmed in 71 of 88 patients by culture and/or histological stain of gastric biopsies. Serum IgG antibody to H. pylori was also measured and resulted in 97% sensitivity and 94% specificity. H. pylori DNA was detected by the PCR assay in gastric biopsy specimens from all 71 patients (100% sensitivity) with proven gastric H. pylori infection but not from 17 noninfected patients (100% specificity). In saliva specimens, H. pylori DNA was identified in 57 of the 68 patients (84%) with proven gastric H. pylori infection and in three of the 17 patients without gastric H. pylori infection. However, the PCR assay was only able to detect H. pylori DNA in the feces from 15 of 61 patients (25%) with proven gastric H. pylori infection and one of the 10 patients without gastric H. pylori infection. The results show that the PCR assay is reliable for detecting the presence of H. pylori in gastric biopsy and saliva specimens. The data indicate that H. pylori exists in a higher prevalence in saliva than feces and that the fecal-oral route may be an important means of transmission of this infection in developing countries but not as significant as previously suspected in the developed countries. It is likely that the oral-oral route is more prominent.

Identification methods for campylobacters, helicobacters, and related organisms

The organisms which are referred to as campylobacteria are associated with a diverse range of diseases and habitats and are important from both clinical and economic perspectives. Accurate identification of these organisms is desirable for deciding upon appropriate therapeutic measures, and also for furthering our understanding of their pathology and epidemiology. However, the identification process is made difficult because of the complex and rapidly evolving taxonomy, fastidious nature, and biochemical inertness of these bacteria. These problems have resulted in a proliferation of phenotypic and genotypic methods for identifying members of this group. The purpose of this review is to summarize the problems associated with identifying campylobacteria, critically appraise the methods that have been used for this purpose, and discuss prospects for improvements in this field.

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.

Development of a rapid PCR method for identification of Helicobacter pylori in dental plaque and gastric biopsy specimens

A rapid and simple polymerase chain reaction (PCR) method was developed to detect Helicobacter pylori in gastric biopsy specimens and dental plaque samples. The primers were targeted to the 16S rRNA sequence of Helicobacter pylori strain ATCC 43504. The system was found to have a theoretical detection level of 0.5 to 5 Helicobacter pylori cells in a 5 microliters sample of dental plaque. In the absence of plaque, the detection level was even better: theoretically, 0.05 to 0.5 Helicobacter pylori cells were detected in water suspension. However, this appeared to be due to the presence of free bacterial DNA in the culture used for the sensitivity determination. Thus, the actual sensitivity of the system was found to be fewer than five Helicobacter pylori cells, irrespective of the type of sample used. The method was then used to analyse 29 dental plaque and gastric biopsy specimens collected from patients with a history of recurrent peptic ulcer disease. Fourteen stomach specimens were positive for Helicobacter pylori when tested with the PCR method, while the respective figures with culture, histological examination and the urease test were 11, 12 and 9. No positive dental plaque samples were observed.

High prevalence of Helicobacter pylori in saliva demonstrated by a novel PCR assay

AIMS

To investigate the prevalence of Helicobacter pylori in the saliva of patients infected with this bacterium.

METHODS

A novel polymerase chain reaction (PCR) assay was developed to detect H pylori in saliva and gastric biopsy specimens from patients undergoing endoscopy.

RESULTS

Our PCR assay amplified a 417 base pair fragment of DNA from all 21 DNAs derived from H pylori clinical isolates but did not amplify DNA from 23 non-H pylori strains. Sixty three frozen gastric biopsy and 56 saliva specimens were tested. H pylori specific DNA was detected by PCR in all 39 culture positive biopsy specimens and was also identified from another seven biopsy specimens which were negative by culture but positive by histology. H pylori specific DNA was identified by PCR in saliva specimens from 30 (75%) of 40 patients with H pylori infection demonstrated by culture or histological examination, or both, and in three patients without H pylori infection in the stomach.

CONCLUSION

The results indicate that the oral cavity harbours H pylori and may be the source of infection and transmission.

Isolation of Helicobacter pylori from saliva

Helicobacter pylori was grown in low numbers from the saliva of one of nine patients who were positive for gastric H. pylori. The saliva-derived isolate from this patient was identical to the antral biopsy-derived isolate from the same patient and differed from isolates cultured from the antral biopsies of all other patients by soluble-protein electrophoresis, restriction endonuclease DNA analysis, and Southern blot hybridization. This is the first observation, to our knowledge, of the recovery of viable H. pylori from saliva.