Helicobacter pylori strains from 299 patients were tested in six laboratories in different countries. Macrolide susceptibility of the strains was determined by agar dilution (17.4%) or the epsilometer test (82.6%). Mutations in the 23S ribosomal DNA (rDNA) that are associated with macrolide resistance were analyzed by PCR and reverse hybridization (PCR-line probe assay [LiPA]). This method identifies A2115G, G2141A, A2142G, A2142C, A2142T, A2143G, and A2143C mutations in the 23S rDNA. vacA s-region (s1a, s1b, s1c, and s2) and m-region (m1, m2a, and m2b) genotypes and cagA status were also determined using another PCR-LiPA system. Of the 299 strains investigated by MIC testing, 130 (43.5%) were resistant and 169 (56.5%) were susceptible to clarithromycin. Of the 130 resistant strains, 127 (97.7%) contained 23S rDNA mutations, whereas 167 (98.8%) of the 169 susceptible strains contained wild-type sequences. The predominant mutations were A2143G (45.2%) and A2142G (33.3%). Twenty-eight (19.8%) strains contained multiple 23S rDNA mutations. Only five resistant strains contained the A2142C mutation (three of these in combination with the A2142G mutation), and the A2115G, G2141A, A2142T, and A2143C mutations were not found. MICs of clarithromycin for the A2142G mutant strains were significantly higher than MICs for the A2143G strains. Although there was no significant association between 23S rDNA mutations and the vacA and cagA status, clarithromycin-susceptible strains more often contained mixed vacA genotypes, indicating the presence of multiple H. pylori strains. In conclusion, our data confirmed the very strong association between 23S rDNA mutations and macrolide resistance and showed that the PCR-LiPA permits accurate and reliable diagnosis of macrolide resistance in H. pylori.

Background-Virulence factors of Helicobacter pylori are associated with peptic ulcer disease and may be also associated with the eYcacy of treatment. Aims-To determine the relation between the vacA and the cagA status of H pylori, clinical disease, and treatment outcome. Patients-121 patients with H pylori infection and peptic ulcer disease or functional dyspepsia were treated by quadruple antibiotic therapy in two groups for one and two days, respectively. Methods-DNA was isolated from gastric antral biopsy specimens, taken before and after treatment, and the vacA and cagA status was determined by polymerase chain reaction and reverse hybridisation. Results-Peptic ulcer disease was significantly associated with the vacA s1 type, and cagA positivity, but not with the vacA m type. Treatment eYcacy was significantly higher in patients with peptic ulcer disease, or infected with cagA+/vacA s1 strains. Conclusions-The strong association between the cagA and vacA status and peptic ulcer disease was confirmed. Cure rates seem to be higher for patients with cagA+/ vacA s1 H pylori strains, which is consistent with the higher cure rate observed among ulcer patients compared with functional dyspepsia patients. Therefore, treatment studies may require stratification for presence of ulcers as well as H pylori genotypes. (Gut 2000;46:321-326)

Helicobacter pylori strains can be distinguished by genotyping of virulence-associated genes, such as vacA and cagA. Because serological discrimination between strain types would reduce the need for endoscopy, 61 patients carrying H. pylori were studied by vacA and cagA genotyping of H. pylori in gastric biopsy specimens and by detection of specific serum antibodies. Serological responses to H. pylori were determined by Helicoblot (versions 2.0 and 2.1). Antibodies to CagA also were determined by a rapid anti-CagA assay (Pyloriset screen CagA) as well as by two noncommercially developed enzyme immunoassays, each using a recombinant CagA protein. Helicobacter pylori persistently colonizes the mucosa of the human stomach, causes chronic gastritis, and is an important risk factor for gastroduodenal diseases, such as peptic ulcers and gastric carcinoma (11). There is increasing evidence that distinct variants of H. pylori exist and that these may be associated with the pathogenicity of the bacterium (41); several virulence-associated genes have been identified (1,8).vacA encodes a vacuolating toxin that is released by H. pylori and injuries epithelial cells (9,21). vacA is present in all H. pylori strains, and includes two variable regions (1). The s region (encoding the signal peptide) is located at the 5Ј end of the gene and exists as an s1 or s2 allele. Within type s1, several subtypes (s1a, s1b, and s1c) can be distinguished (39). The m region (middle) occurs as an m1 or m2 allele. The mosaic combination of s-and m-region allelic types correlates with the production of the cytotoxin and is thereby associated with virulence of the bacterial strain (1).cagA (cytotoxin-associated gene) is considered a marker for the presence of the pathogenicity (cag) island of about 35 kbp (6). Carriage of cagA ϩ strains increases the risk for the development of atrophic gastritis and gastric cancer (4,19). Several studies have shown clinical relevance of specific antibodies to CagA using noncommercial assays (3,5,7,20,29,(33)(34)(35)44), whereas others failed to confirm these findings (14,17,18,23,27,45) H. pylori can be diagnosed by analysis of gastric biopsy specimens by urease tests, culture of the bacterium, histopathology, or detection of bacterial DNA by PCR. Noninvasive diagnostic methods include the urea breath test and serological assays measuring antibodies to H. pylori in the serum (15,22). The distinct vacA and cagA genotypes of H. pylori can best be identified by molecular methods, using cultured strains, or directly in gastric biopsy specimens, but this requires endoscopy. Therefore, serological typing methods analyzing specific antibodies to H. pylori if accurate, would be most suitable for routine clinical use. The present study assessed the relationship between the vacA and cagA genotypes of H. pylori and the presence of specific anti-Helicobacter antibodies, in particular, antibodies to CagA. MATERIALS AND METHODSPatients. Gastric (antral) biopsy specimens and serum samples were obtained from patients, undergoin...

A total of 500 consecutive patients undergoing upper endoscopy were biopsied and tested for H. pylori infection by the Campylobacter -like organism (CLO) test, culture, histology, and PCR. Serum samples were tested by two different serological assays. Patients were considered H. pylori positive if at least two of the four biopsy specimen-based methods yielded positive results. PCR had the highest diagnostic sensitivity (99.4%), followed by histology (92.2%), culture (89.5%), and the CLO test (89.0%). The specificities of all methods were higher than 98%. Of the organisms from the 181 PCR-positive patients, the vacA (s and m regions), cagA , and iceA genotypes were determined by reverse hybridization (line probe assay) or an allele-specific PCR. Organisms that were detected by PCR but that remained undetected by the CLO test were significantly more often vacA s1 ( P = 0.006), m1 ( P = 0.028), and cagA positive ( P = 0.029) than vacA s2, m2, and cagA negative, respectively. Organisms that were detected by PCR but that remained undetected by culture or histology more often contained iceA1 ( P = 0.034 and P = 0.029, respectively) than iceA2 . Higher H. pylori density was associated with vacA s2 ( P = 0.024), vacA m2 ( P = 0.050), and cagA -negative ( P = 0.035) genotypes. Also, the diagnostic results of the CLO test ( P = 0.001) and culture ( P = 0.031) but not those of the PCR ( P = 0.130) were significantly associated with the H. pylori density. The rate of detection by the four biopsy specimen-based tests was lower for patients who used proton pump inhibitors, but this was independent of the H. pylori genotypes. These observations may be explained by different bacterial densities, as established by the distinct genotypes of H. pylori , and confirm that the biologies of strains with such genotypes are considerably different.