Virulence of infecting Helicobacter pylori strains and intensity of mononuclear cell infiltration are associated with levels of DNA hypermethylation in gastric mucosae

DNA methylation changes are known to occur in gastric cancers and in premalignant lesions of the gastric mucosae. In order to examine variables associated with methylation levels, we quantitatively evaluated DNA methylation in tumors, non-tumor gastric mucosae, and in gastric biopsies at promoters of 5 genes with methylation alterations that discriminate gastric cancers from non-tumor epithelia (EN1, PCDH10, RSPO2, ZIC1, and ZNF610). Among Colombian subjects at high and low risk for gastric cancer, biopsies from subjects from the high-risk region had significantly higher levels of methylation at these 5 genes than samples from subjects in the low risk region (p ≤ 0.003). When results were stratified by Helicobacter pylori infection status, infection with a cagA positive, vacA s1m1 strain was significantly associated with highest methylation levels, compared with other strains (p = 0.024 to 0.001). More severe gastric inflammation and more advanced precancerous lesions were also associated with higher levels of DNA methylation (p ≤ 0.001). In a multivariate model, location of residence of the subject and the presence of cagA and vacA s1m1 in the H. pylori strain were independent variables associated with higher methylation in all 5 genes. High levels of mononuclear cell infiltration were significantly related to methylation in PCDH10, RSPO2, and ZIC1 genes. These results indicate that for these genes, levels of methylation in precancerous lesions are related to H. pylori virulence, geographic region and measures of chronic inflammation. These genes seem predisposed to sustain significant quantitative changes in DNA methylation at early stages of the gastric precancerous process.

Non-invasive genotyping of Helicobacter pylori cagA, vacA, and hopQ from asymptomatic children

BACKGROUND

Helicobacter pylori infection is usually acquired in childhood, but little is known about its natural history in asymptomatic children, primarily due to the paucity of non-invasive diagnostic methods. H. pylori strains harboring cagA and specific alleles of hopQ and vacA are associated with increased risk for gastric cancer. Many studies of H. pylori virulence markers in children have the bias that symptomatic subjects are selected for endoscopy, and these children may harbor the most virulent strains. Our aim is to genotype cagA, hopQ, and vacA alleles in stool DNA samples of healthy Colombian children residing in an area with high incidence of gastric cancer, to avoid selection bias resulting from endoscopy.

METHODS

H. pylori status of 86 asymptomatic children was assessed by (13) C-urea breath test (UBT) and PCR. H. pylori 16S rRNA, cagA, hopQ, and vacA genes were amplified from stool DNA samples and sequenced.

RESULTS

UBT was positive in 69 (80.2%) of 86 children; in stool DNA analysis, 78.3% were positive by 16S rRNA PCR. cagA, vacA, and hopQ were detected in 66.1%, 84.6%, and 72.3% of stool DNA samples from 16S rRNA-positive children. Of the children's DNA samples, which revealed vacA and hopQ alleles, 91.7% showed vacA s1 and 73.7% showed type I hopQ. Type I hopQ alleles were associated with cagA positivity and vacA s1 genotypes (p < 0.0001).

CONCLUSIONS

Using stool DNA samples, virulence markers of H. pylori were successfully genotyped in a high percentage of the asymptomatic infected children, revealing a high prevalence of genotypes associated with virulence. Type I hopQ alleles were associated with the presence of cagA and the vacA s1 genotype.

Capsaicin consumption, Helicobacter pylori CagA status and IL1B-31C>T genotypes: a host and environment interaction in gastric cancer

Gastric cancer (GC) has been associated with a complex combination of genetic and environmental factors. In contrast to most countries, available information on GC mortality trends showed a gradual increase in Mexico. Our aim was to explore potential interactions among dietary (chili pepper consumption), infectious (Helicobacter pylori) and genetic factors (IL1B-31 genotypes) on GC risk. The study was performed in three areas of Mexico, with different GC mortality rates. We included 158 GC patients and 317 clinical controls. Consumption of capsaicin (Cap), the pungent active substance of chili peppers, was estimated by food frequency questionnaire. H. pylori CagA status was assessed by ELISA, and IL1B-31 genotypes were determined by TaqMan assays and Pyrosequencing in DNA samples. Multivariate unconditional logistic regression was used to estimate potential interactions. Moderate to high Cap consumption synergistically increased GC risk in genetically susceptible individuals (IL1B-31C allele carriers) infected with the more virulent H. pylori (CagA+) strains. The combined presence of these factors might explain the absence of a decreasing trend for GC in Mexico. However, further research on gene-environment interactions is required to fully understand the factors determining GC patterns in susceptible populations, with the aim of recommending preventive measures for high risk individuals.

Phylogeographic origin of Helicobacter pylori is a determinant of gastric cancer risk

BACKGROUND AND AIMS

Helicobacter pylori colonises the stomach in half of all humans, and is the principal cause of gastric cancer, the second leading cause of cancer death worldwide. While gastric cancer rates correlate with H pylori prevalence in some areas, there are regions where infection is nearly universal, but rates of gastric cancer are low. In the case of Colombia, there is a 25-fold increase in gastric cancer rate in the Andean mountain (high risk) region compared to the coastal (low risk) region, despite similarly high (∼90%) prevalence of H pylori in the two locations. Our aim was to investigate the ancestral origin of H pylori strains isolated from subjects in these high- and low-risk regions and to determine whether this is a predictive determinant of precancerous lesions.

METHODS

Multi-locus sequence typing was used to investigate phylogeographic origins of infecting H pylori strains isolated from subjects in the Pacific coast and Andes Mountains in the state of Nariño, Colombia. We analysed 64 subjects infected with cagA+ vacA s1m1 strains. Gastric biopsy slides from each individual were scored for histological lesions and evaluated for DNA damage by immunohistochemistry.

RESULTS

We show that strains from the high-risk region were all of European phylogeographic origin, whereas those from the low risk region were of either European (34%) or African origin (66%). European strain origin was strongly predictive of increased premalignant histological lesions and epithelial DNA damage, even in the low-risk region; African strain origin was associated with reduced severity of these parameters.

CONCLUSION

The phylogeographic origin of H pylori strains provides an explanation for geographic differences in cancer risk deriving from this infection.

Promoter DNA hypermethylation in gastric biopsies from subjects at high and low risk for gastric cancer

Gene promoter CpG island hypermethylation is associated with Helicobacter pylori (H. pylori) infection and may be an important initiator of gastric carcinogenesis. To examine factors influencing methylation, we utilized bisulfite Pyrosequencing® technology for quantitative analysis of promoter DNA methylation in RPRM, APC, MGMT and TWIST1 genes using DNA from 86 gastric biopsies from Colombian residents of areas with high and low incidence of gastric cancer. H. pylori colonies were cultured from the same subjects, and gastric pathology was evaluated. Virulence factors cagA (including segments of the 3' end, encoding EPIYA polymorphisms) and vacA s and m regions were characterized in the H. pylori strains. Using univariate analysis, we found significantly elevated levels of RPRM and TWIST1 promoter DNA methylation in biopsies from residents of the high-risk region compared to those from residents of the low-risk region. The presence of cagA and vacA s1m1 alleles were independently associated with elevated levels of promoter DNA methylation of RPRM and MGMT. Using multivariate analysis, DNA methylation of RPRM was associated with location of residence, cagA and vacA s1m1 status and methylation of TWIST1. We conclude that cagA and vacA virulence determinants are significantly associated with quantitative differences in promoter DNA methylation in these populations, but that other as yet undefined factors that differ between the populations may also contribute to variation in methylation status.

Abstract A77: Gastric cancer risk in relation to capsaicin intake, H. pylori CagA status, and IL1B-31 C&gt;T genotypes

Background: In contrast to the situation in most countries, gastric cancer (GC) incidence is not declining in Mexico. Capsaicin (Cap) is the pungent active substance of chili peppers and it is related to an increased risk of GC in studies performed in Mexico, Spain, Serbia, Korea and India. Host genetic characteristics and variations in dietary patterns are considered concomitant risk factors for GC development. Helicobacter pylori (H. pylori) infection is considered a necessary but not sufficient cause of GC, as less than 3 % of infected patients develop this tumor. Increased risk for GC has been observed among Mexican C allele carriers of the pro-inflammatory interleukin 1B position-31 (IL1B-31) infected with more virulent H. pylori CagA = strains, we explored if that risk varies according to the consumption of Cap, since chili pepper consumption is highly prevalent among Mexicans.

Methods: A total of 158 histologically confirmed GC patients and 317 clinical controls from three states with contrasting GC mortality rates in Mexico were included in this report. Cap intake was estimated by a previously validated food frequency questionnaire. H. pylori CagA status was assessed by an ELISA test, and genotypes of the IL1 B-31 were determined byTaqMan assays and Pyrosequencing in DNA samples isolated from serum.

Results: Using unconditional adjusted logistic regression models, a significant 3.5-fold increased GC risk was observed among individuals with moderate to high Cap consumption, who were IL1B-31 C allele carriers and were H. pylori CagA positive, with a significant interaction term between Cap consumption and IL1B-31 genotypes (p=0.039): Odds Ratio (OR) among TC vs.TT carriers: 3.48; 95%CI: 1.01-12.0, and OR among CC vs. TT carriers: 3.37; 95%CI: 1.05-10.85; in contrast, no significant negative associations with GC were estimated when any of these three factors was absent.

Conclusions. This is the first epidemiological report considering a potential interaction amongst dietary, infectious and genetic factors on GC risk and suggests that moderate to high Cap intake synergistically increases the risk of GC in genetically susceptible individuals (IL1 B-31 C allele carriers) infected with more virulent H. pylori (CagA positive) strains. The significant interaction between Cap consumption and genotypes of the IL1 B-31 suggests that a reduction of Cap intake under 30 mg/day among susceptible carriers with high consumption of Cap would reduce GC risk. Underlying mechanisms that explain these results, warrant attention and may include an up-regulation of H. pylori CagA expression in response to high capsaicin consumption.

Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):A77.

Role of Helicobacter pylori CagA molecular variations in induction of host phenotypes with carcinogenic potential

Helicobacter pylori cagA-positive strains exert population-specific risks for gastric cancer. We determined whether variations in CagA phosphorylation motifs were associated with carcinogenic or proinflammatory epithelial phenotypes induced by strains from regions with divergent cancer risks (Colombia and Nashville, TN). Motif number was significantly related to levels of CagA phosphorylation and cytoskeletal abnormalities. Precancerous isolates possessed a higher number of motifs, and precancerous strains from Nashville induced higher levels of IL-8 than Colombian strains. These results indicate that CagA variants are linked with premalignant lesions in distinct populations and that epithelial responses to these strains are selective based upon locale.

CagA C-terminal variations in Helicobacter pylori strains from Colombian patients with gastric precancerous lesions

The C-terminus of the Helicobacter pylori CagA protein is polymorphic, bearing different EPIYA sequences (EPIYA-A, B, C or D), and one or more CagA multimerization (CM) motifs. The number of EPIYA-C motifs is associated with precancerous lesions and gastric cancer (GC). The relationship between EPIYA, CM motifs and gastric lesions was examined in H. pylori-infected Colombian patients from areas of high and low risk for GC. Genomic DNA was extracted from H. pylori strains cultured from gastric biopsies from 80 adults with dyspeptic symptoms. Sixty-seven (83.8%) of 80 strains were cagA positive. The 3' region of cagA was sequenced, and EPIYA and CM motifs were identified. CagA proteins contained one (64.2%), two (34.3%) or three EPIYA-C motifs (1.5%), all with Western type CagA-specific sequences. Strains with one EPIYA-C motif were associated with less severe gastric lesions (non-atrophic and multifocal atrophic gastritis), whereas strains with multiple EPIYA-C motifs were associated with more severe lesions (intestinal metaplasia and dysplasia) (p <0.001). In 54 strains, the CM motifs were identical to those common in Western strains. Thirteen strains from the low-risk area contained two different CM motifs: one of Western type located within the EPIYA-C segment and another following the EPIYA-C segment and resembling the CM motif found in East Asian strains. These strains induced significantly shorter projections in AGS cells and an attenuated reduction in levels of CagA upon immunodepletion of SHP-2 than strains possessing Western/Western motifs. This novel finding may partially explain the difference in GC incidence in these populations.

Eosinophils and mast cells in chronic gastritis: possible implications in carcinogenesis

Eosinophils and mast cells participate in the immune response against Helicobacter pylori, but their involvement in the gastric precancerous process is unclear. This study aimed to estimate eosinophil and mast cell density in antral mucosa in subjects from 2 Colombian populations with contrasting gastric cancer risks. Gastric mucosa biopsies were collected from 117 adult males (72 from a high-risk area and 45 from a low-risk area). A histopathology score was used to quantify severity of the lesions. Quantitation of eosinophils in hematoxylin-eosin-stained sections and mast cells in immunostained sections for CD117/c-Kit was performed. Helicobacter pylori infection and genotyping were assessed in Steiner stain and polymerase chain reaction, respectively. Logistic regression models and semiparametric cubic smoothing splines were used for analysis of the results. Eosinophil density was significantly higher in subjects from the low-risk area as compared with subjects from the high-risk area. In both populations, eosinophil density increased with the histopathology score in the progression of lesions from normal morphology to multifocal atrophic gastritis. Intestinal metaplasia and dysplasia specimens showed further increase in eosinophil density in the high-risk area but an abrupt decrease in the low-risk area. Mast cell density increased in parallel to the histopathology score in both populations. Our results suggest that eosinophils play a dual role in chronic gastritis. In the low-risk area, elevated eosinophil density represents a T helper 2-biased response that may down-regulate the effects of proinflammatory cytokines preventing cancer development. In contrast, in the high-risk area, eosinophils might promote a T helper 1-type response leading to progression of precancerous lesions.

Helicobacter pylori genotyping and sequencing using paraffin-embedded biopsies from residents of colombian areas with contrasting gastric cancer risks

BACKGROUND

cagA-positive and vacA s1 and m1 genotypes of Helicobacter pylori are associated with an elevated risk of gastric cancer (GC). We determined these genotypes using paraffin-embedded gastric biopsy specimens harvested from infected individuals and compared genotype distributions in two Colombian populations residing in geographic regions with a high and low incidence of GC.

METHODS

DNA from paraffin-embedded gastric biopsies from 107 adults was amplified using primers specific for cagA, for the cag'empty site', for the s and m alleles of vacA, and for H. pylori 16S rRNA.

RESULTS

H. pylori infection was detected by molecular assays in 97 (90.7%) biopsies. Complete genotyping of cagA and vacA was achieved in 94 (96.9%) cases. The presence of cagA was detected in 78 of 97 cases (80.4%); when considered separately, cagA and vacA s regions were not significantly associated with a particular geographic area. The vacA m1 allele and s1m1 genotypes were more common in the area of high risk for GC (p = .037 and p = .044, respectively), while the vacA m2 allele and s2m2 genotypes were more prevalent in the low-risk area. The prevalence of the combination of cagA-positive, vacA s1m1 genotypes was 84.3% and 60.5% for high and low risk areas, respectively (p = .011).

CONCLUSIONS

H. pylori cagA and vacA genotyping from paraffin-embedded gastric biopsies permitted reliable typability and discrimination. The more virulent cagA-positive s1m1 strains, as well as vacA m1 genotype, were more prevalent in high risk than in low risk areas, which may contribute to the difference in GC risk between those two regions.

Cytokine polymorphisms and gastric cancer risk: an evolving view

More than 20 years after the identification of Helicobacter pylori as a human pathogen, gastric cancer continues to be a leading cause of cancer deaths worldwide. Genetic association studies have the potential for helping to identify those at greatest risk for developing gastric cancer subsequent to infection by H. pylori. IL1B promoter polymorphisms have been supported by several meta-analyses as being associated with gastric cancer risk. In this review, we discuss challenges in experimental design of gene association studies in gastric cancer, with attention to gene-environment interactions that may lead to inconsistency in findings across populations.

Gastric cancer risk in a Mexican population: role of Helicobacter pylori CagA positive infection and polymorphisms in interleukin-1 and -10 genes

Several polymorphisms of the IL1B and IL10 gene promoters have been reported to be associated with gastric cancer risk in Caucasians. However, studies in other populations have shown differing results. We aimed to test for associations between polymorphisms in IL1B (-31 and +3954), IL10-592 and IL1RN variable number of tandem repeats (VNTR) and risk of gastric cancer in a Mexican population. DNA was extracted from sera of 183 gastric adenocarcinoma patients and 377 controls. The IL1B-31, IL1B+3954 and IL10-592 biallelic polymorphisms were discriminated using 5' Nuclease (TaqMan) assays and Pyrosequencing. The IL1RN penta-allelic VNTR polymorphism was genotyped using PCR followed by GeneScan analysis. A significant interaction was found between IL1B-31 and CagA status for the risk of intestinal-type gastric cancer (p = 0.023). Among CagA positive subjects, those with IL1B-31CC genotype had an increased risk of intestinal-type gastric cancer (OR 3.19, 95%CI = 1.05-9.68), compared to carriers of IL1B-31TT genotype. In contrast, among CagA negative subjects, no significant association of IL1B-31CC genotype with gastric cancer was observed. The IL10-592CC genotype was associated with more than doubling of the risk of the intestinal-type gastric cancer (OR, 2.20, 95%CI = 1.04-4.65). A nonsignificantly increased risk for intestinal-type gastric cancer was found in IL1RN*2 carriers (OR 1.49, 95%CI = 0.89-2.50). None of these polymorphisms was significantly related to the risk of diffuse-type gastric cancer. No significant association was found between risk of gastric cancer and the IL1B+3954 polymorphism. Individuals carrying 2 or more of the risk-associated alleles (IL1B-31C, IL1RN *2 and IL10-592C) were at increased risk for intestinal-type gastric cancer, compared to those with 0 or 1 risk-associated allele. The risk from multiple risk-associated alleles was especially high in subjects infected with CagA positive H. pylori. Our results support the identification of the IL1B-31 promoter polymorphism as a useful marker for risk of intestinal type gastric cancer in persons with CagA positive H. pylori infections.

Association of interleukin-1beta gene polymorphisms with precancerous gastric lesions in African Americans and Caucasians

OBJECTIVE

Interleukin-1beta plays an important role in inflammation and gastric physiology. Polymorphisms of the IL1B gene have been associated with gastric atrophy and increased cancer risk, especially in Helicobacter pylori-infected subjects. The aim of this study was to evaluate the relationship between IL1B and IL1 receptor antagonist gene polymorphisms and the risk of multifocal atrophic gastritis in African Americans and Caucasians.

METHODS

Genomic DNA was extracted from gastric biopsies of 269 adult outpatients (172 African Americans and 97 Caucasians) undergoing diagnostic upper gastrointestinal endoscopy. Histological diagnosis was evaluated according to the updated Sydney System and H. pylori status was assessed by Steiner silver stain. Polymorphisms of the IL1B gene (-511, -31, and +3954) and the IL1 receptor antagonist were investigated by PCR-RFLP. Logistic regression models were used to identify variables associated with multifocal atrophic gastritis in terms of odds ratios and 95% confidence intervals.

RESULTS

Considering subjects with normal histology and nonatrophic gastritis as controls, a significant association was found between IL1B+3954T carrier and multiatrophic gastritis (OR 2.23, 95% CI 1.28, 3.88). Analyses stratified by ethnic group demonstrated similar associations in both African Americans (OR 2.23, 95% CI 1.14, 4.37) and Caucasians (OR 2.04, 95% CI 0.74, 5.65). A positive but not significant association was found between the allele 2 of the IL1RN and the presence of multifocal atrophic gastritis. The remaining proinflammatory polymorphisms were not associated with this precancerous lesion.

CONCLUSIONS

Our results suggest that the presence of IL1B+3954T allele is a risk marker for multifocal atrophic gastritis in the population studied.

A positive assay for identification of cagA negative strains of Helicobacter pylori

A new PCR protocol was developed for the positive identification of cagA negative Helicobacter pylori strains. Amplification of a portion of the genome across the insertion point of the cag pathogenicity island (the ES-"empty site") generated a 106-bp fragment, which produces a positive signal for cagA negative strains. Combined with the results of the cagA assay, the signals for ES allowed the complete characterization of the patients' cagA status. DNA sequencing analysis confirmed the identity of the ES fragment. The new protocol and cagA assay were applied to 22 DNA preparations isolated from stools from H. pylori infected adult patients and to 21 DNA preparations isolated from stools from H. pylori infected children. The same analysis was also performed on nine colonies of H. pylori derived from gastric biopsies of nine of the adult patients. The total number of cagA positive cases from adult patients was 14 or 63.6% (11 mono- and 3 mixed) and of the cagA negative cases (or ES positive) was 9 or 40.9% (6 mono- and 3 mixed). Of the 21 stool DNA samples from children, 6 (28.6%) were cagA positive, 12 (57.1%) were cagA negative and 3 (14.3%) were positive for cagA and for the ES simultaneously. The proportions of mixed cagA positive and cagA negative H. pylori infections were almost equal in adults and children (13.6% and 14.3%, respectively). No reaction products of the proper fragment sizes for cagA or the empty site (ES) were obtained from any of the stool DNA samples of 10 H. pylori uninfected subjects (100% specificity). This noninvasive assay discriminates consistently cagA negative cases from cagA positive strains and from amplification failures. It can be a useful tool for clinical and epidemiological studies of H. pylori infection.

Comparison of genotyping of Helicobacter pylori cagA and vacA virulence genes from gastric biopsies and stool specimens

BACKGROUND

We compared results of genotyping of Helicobacter pylori cagA and vacA virulence genes in DNA from gastric biopsies, both paraffin-embedded and frozen, and from stool samples, in order to evaluate the comparative sensitivity of the stool assay.

METHODS

Genomic DNA from paraffin-embedded biopsies, unfixed frozen biopsies, and stool samples of the same 20 patients was amplified for the cagA gene, an empty site (which provides a positive signal for cagA negative strains) and for the s and m alleles of the vacA gene. Composite genotypes were determined by combining data from analysis of all three materials.

RESULTS

Analysis of none of the materials taken singly showed all of the genotypes revealed by all three materials taken together, probably because of sampling error. Analysis of paraffin biopsies revealed 83.5%, that of frozen biopsies revealed 74.7% and that of stools revealed 75.9% of the genotypes. There was no significant difference in the percentage of the H. pylori genotypes identified from the three materials. Analysis of combinations of frozen biopsies and stools revealed 89.9% of the composite genotypes, and that of paraffin biopsies and stools revealed 96.2% of the composite genotypes. Evidence of multiple genotypes was found in 10 of 20 (50%) of the cases.

CONCLUSIONS

Any one of the investigated biological materials can be used for detection of cagA and vacA genes, but no single assay provided a complete genotype. The use of a combination of two materials may generate a more accurate representation of H. pylori genotypes in each individual.

Detection and typing of Helicobacter pylori cagA/vacA genes by radioactive, one-step polymerase chain reaction in stool samples from children

The detection and molecular typing of Helicobacter pylori virulence genes in human stool specimens by polymerase chain reaction (PCR) require an adequate amount of bacterial DNA and an appropriately adjusted PCR protocol. DNA was isolated from stool samples of 39 H. pylori-infected and nine uninfected Colombian children using the QIAamp Kit following the manufacturer's instructions but with modifications. DNA templates were amplified for the vacA s and m regions and for the cagA gene by PCR using radioactively labeled (32P) primers. The modifications in the standard Qiagen protocol of stool DNA extraction increased the final concentration of eluted total stool DNA 4.7 times (117 +/- 17 versus 22 +/- 3 ng/microl; P < 0.0001). Nevertheless, its amplification by regular PCR programs (30-40 cycles) did not generate visible signals because of the very low ratio of H. pylori DNA to other DNA. PCR for 80 cycles successfully amplified vacA in 36/39 samples (sensitivity, 92.3%) and cagA fragments in 21/39 (53.8%) fecal DNA samples. Both s and m vacA regions were amplified in 33/36 (91.7%) DNA samples. The s1m1 genotype was the most commonly isolated variant, accounting for 17/36 or 47.2% of positive samples. The s2m2 genotype was ascertained to be frequent also (14/36 or 38.9%). Almost all (94.1%) s1m1 genotypes were cagA positive. The majority of s2m2 genotypes (78.6%) were not associated with the cagA gene. Neither cagA nor vacA fragments were amplified from DNA isolates of H. pylori-uninfected children nor from DNA isolated from six gastrointestinal bacterial strains (specificity, 100%). The data suggest that the proposed modified technique of DNA extraction and PCR assay of stool samples may be an effective and reliable noninvasive tool for the detection and typing of H. pylori cagA/vacA virulence genes in infected individuals.

Enrichment medium for isolation of Campylobacter jejuni-Campylobacter coli

A kaseini-broth enrichment medium (KBEM) for the isolation improvement of Campylobacter jejuni-Campylobacter coli from stool samples is described. Isolation of Campylobacters from stool specimens by direct inoculation onto solid selective medium was compared with isolation after twenty-four hours enrichment at 37 degrees C in KBEM, followed by subculture onto the same solid selective medium. Of 156 examined stool samples from diarrhoeal children positive results were obtained from 17 patients altogether: 11 by direct inoculation on selective media and 6 only owing to enrichment. Thus, an increase of 35.3% in the isolation rate was obtained by using the enrichment medium. The same medium allows the preservation of isolates of Campylobacter jejuni-Campylobacter coli for 2 months and longer at 37 degrees C.