Helicobacter pylori cagA, vacA, and iceA genotypes and clinical outcomes: a cross-sectional study in central Vietnam.

Helicobacter pylori is the most common cause of gastroduodenal diseases. The concept that cagA-positive H. pylori is a risk factor for gastric cancer appears to be true only for H. pylori strains from Western countries. Other virulent genes may have a synergistic interaction with cagA during pathogenesis. This study aims to investigate H. pylori cagA, vacA, and iceA prevalence, genotypes, and their association to clinical outcomes in Vietnamese patients. The cagA status and vacA and iceA genotypes were determined using the PCR technique on DNA extracted from gastric biopsies of 141 patients with gastroduodenal diseases. After performing molecular analysis for cagA, vacA, and iceA genes, samples with mixed H. pylori strains, positivity, or negativity for both cagA and cagPAI-empty site, or unidentified genotypes were excluded. Finally, 107 samples were examined. The presence of the cagA, vacA, and iceA genes were detected in 77.6%, 100%, and 80.4% of cases, respectively. Notably, cagA( +) with EPIYA-ABD, vacA s1i1m1, vacA s1i1m2, iceA1, and iceA2 accounted for 73.8%, 44.9%, 33.6%, 48.6%, and 31.8% of cases, respectively. Four iceA2 subtypes (24-aa, 59-aa, 94-aa, and 129-aa variants) were found, with the 59-aa variant the most prevalent (70.6%). The cagA( +)/vacAs1i1m1/iceA1 and cagA( +)/vacAs1i1m2/iceA1 combinations were found in 26.2% and 25.1% of cases, respectively. A multivariable logistic regression analysis was performed, after adjusting for age and gender, with the gastritis group was used as a reference control. Statistically significant associations were found between the vacA s1i1m2 genotype, the iceA1 variant, and the cagA( +)/vacAs1i1m2/iceA1 combination and gastric cancer; the adjusted ORs were estimated as 18.02 (95% CI: 3.39-95.81), 4.09 (95% CI: 1.1-15.08), and 16.19 (95% CI: 3.42-76.66), respectively. Interestingly, for the first time, our study found that vacA s1i1m2, but not vacA s1i1m1, was a risk factor for gastric cancer. This study illustrates the genetic diversity of the H. pylori cagA, vacA, and iceA genes across geographical regions and contributes to understanding the importance of these genotypes for clinical outcomes.

Current status of Helicobacter pylori resistance to clarithromycin and levofloxacin in Vietnam: Results from molecular analysis of gastric biopsy specimens.

OBJECTIVES: The management of Helicobacter pylori in Vietnam is becoming progressively more difficult due to increasing antibiotic resistance, particularly to clarithromycin (CLR) and levofloxaxin (LVX). In Vietnam, the selection of an H. pylori eradication regimen is predominantly based on empirical evidence. However, molecular analysis aimed at identifying H. pylori antibiotic-resistant genotypes is a promising method in antibiotic susceptibility testing. In this study, we aimed to determine the rates of genotypic H. pylori resistance to CLR and LVX by using DNA strip technology in Vietnam. METHODS: We performed DNA-strip technology-based testing on 112 patients with H. pylori-positive gastroduodenal diseases to detect 23S rRNA and gyrA mutations. RESULTS: Helicobacter pylori genotypic resistance to CLR and LVX was evident in 81.3% and 53.6% of the patients, respectively, and dual resistance was observed in 48.2%. The 23S rRNA A2142G and A2143G mutations accounted for 1.8% and 79.5% of cases, respectively. The gyrA N87K, D91N, D91G, and D91Y mutations were present in 37.5%, 11.6%, 5.4%, and 5.4% of patients, respectively. All four gyrA mutations were observed in both the naïve and failure patients. We further found an association between the 23S rRNA A2143G mutation and a history of CLR use as well as between the gyrA N87K mutation and a history of LVX use. CONCLUSIONS: We found a very high prevalence of H. pylori resistance to CLR and LVX and dual resistance to these antibiotics in Vietnam. The application of molecular assays is feasible and may improve the management of H. pylori infection in Vietnam.

Deficient Mismatch Repair Proteins in Gastric Mixed Neuroendocrine Non-Neuroendocrine Neoplasm: A Rare Case Report.

Mixed neuroendocrine non-neuroendocrine neoplasm (MiNEN) is a rare type of gastric carcinoma with controversial diagnosis and treatment. Recent data implies that deficiency mismatch repair proteins inducing microsatellite instability are considered one of the potential drivers of this disease. Hence, we report a stomach MiNEN with MMR protein loss. An admitted 60-year-old woman complained of epigastric pain. The pathological analysis of the gastro-endoscopic biopsy specimen revealed gastric adenocarcinoma. The radiological staging was cT3N1M0; therefore, she received D2 distal gastrectomy. Suspecting neuroendocrine component admix with adenocarcinoma part on the resected specimen microscopy, applying biomarkers including AE 1/3, synaptophysin, and chromogranin A to confirm the diagnosis of MiNEN. The neuroendocrine part was classified as neuroendocrine tumor grade 2 with Ki 67 at 16.5%. To further understand the molecular characterization of this disease, we evaluated mismatch protein expression by staining MLH1, MSH2, MSH6, and PMS2 antibodies. Interestingly, both components lost MLH1 and PMS2 proteins. Her radical surgery followed oxaliplatin/capecitabine adjuvant chemotherapy. The patient is still well after eight cycles of chemotherapy. dMMR gastric MiNENs and dMMR gastric cancer share many clinical and genetic characteristics. Further studies are necessary to survey the role of dMMR in the prognosis and treatment of this entity.

An extremely rare missense mutation of the androgen receptor gene in a Vietnamese family with complete androgen insensitivity syndrome.

We report a Vietnamese family with complete androgen insensitivity syndrome that included several phenotypic females who have a 46,XY karyotype with an extremely rare mutation of the androgen receptor gene. The proband was a 27-year-old phenotypic adult female referred to our department for karyotyping due to primary amenorrhea. Ultrasound examination revealed a small uterus. Chromosomal analysis showed a 46,XY karyotype. A polymerase chain reaction assay revealed the presence of the sex-determining region Y gene. Next-generation sequencing detected the NM_000044.6(AR):c.2170C>T(p.Pro274Ser) mutation, which was confirmed by Sanger sequencing. There is only one previous report of this mutation in a child with complete androgen insensitivity syndrome. In the family presented in this study, there were four more phenotypic adult females with primary amenorrhea and a phenotypic female infant with testes in the inguinal canals. The infant (first cousin once removed of the proband) presented with inguinal hernia/swelling in a phenotypic female and one of the four abovementioned adults had similar genetic analysis results. This is the second report of a missense mutation NM 000044.6(AR):c.2170C>T in the world and the first study to document a pedigree consisting of several individuals with CAIS as a result of this mutation. The presence of a tiny uterus in the proband, which is a rare occurrence in complete androgen insensitivity syndrome, is a unique clinical indicator of the disorder's variable expressivity.

Genetic diversity of the oipA gene among Helicobacter pylori isolates and clinical outcome in Vietnam.

Outer inflammatory protein A (OipA), which is encoded by the oipA gene, can induce interleukin-8 secretion in gastric epithelial cells. The functional status of the oipA gene is regulated by the slipped-strand mispairing mechanism based on the CT dinucleotide repeat number in the 5' region. This study aimed to investigate the oipA functional status ("on/off") of Helicobacter pylori (H. pylori) and its association with gastroduodenal diseases in southwestern Vietnam. The cross-sectional study was conducted on 173H. pylori isolates from 173 patients with gastroduodenal diseases. Sanger sequencing was used to determine the functional status of oipA. Multivariable logistic regression analysis was performed to identify the association between oipA status and gastroduodenal diseases. The oipA "on" status accounted for 96% of H. pylori isolates. Twenty-five CT repeat patterns of the oipA 5' signal region were observed, five of which were novel CT repeat patterns. The oipA "on" status was found in 100%, 97.8%, and 86.8% of H. pylori isolates from patients with peptic ulcer, precancerous lesions, and chronic gastritis, respectively (p < 0.01). The oipA "on" status was related to gastric precancerous lesions versus chronic gastritis (adjusted OR = 7.39, 95% CI: 1.35-40.59, p = 0.021) and peptic ulcers versus chronic gastritis (adjusted OR = 12.79, 95% CI: 1.19-1760.32, p = 0.033). Our data show a high prevalence of the oipA "on" status, which was associated with precancerous gastric lesions and peptic ulcers. Moreover, genetic diversity in the number and pattern of CT dinucleotide repeat of oipA among Vietnamese H. pylori strains was identified.

Combined Gap-Polymerase Chain Reaction and Targeted Next-Generation Sequencing Improve α- and ß-Thalassemia Carrier Screening in Pregnant Women in Vietnam.

Vietnam has a high thalassemia burden. We collected blood samples from 5880 pregnant Vietnamese women during prenatal health checks to assess thalassemia carrier frequency using combined gap-polymerase chain reaction (gap-PCR) and targeted next-generation sequencing (NGS). Thalassemia carriers were identified with prevalence of 13.13% (772), including 7.82% (460) carriers of α-thalassemia (α-thal), 5.31% (312) carriers of ß-thalassemia (ß-thal), and 0.63% (37) concurrent α-/ß-thal carriers. Deletional mutations (368) accounted for 80.0% of α-thal carriers, of which, --SEA (Southeast Asian) (n = 254; 55.0%) was most prevalent, followed by the -α3.7 (rightward) (n = 66; 14.0%) and -α4.2 (leftward) (n = 45; 9.8%) deletions. Hb Westmead (HBA2: c.369C>G) (n = 53) and Hb Constant Spring (Hb CS or HBA2: c.427T>C) (in 28) are the two most common nondeletional α-globin variants, accounting for 11.5 and 6.0% of α-thal carriers. We detected 11 different ß-thal genotypes. Hb E (HBB: c.79G>A) (in 211) accounted for 67.6% of ß-thal carriers. The most common ß-thal genotypes were associated with mutations at codon 17 (A>T) (HBB: c.52A>T), codons 41/42 (-TTCT) (HBB: c.126_129delCTTT), and codon 71/72 (+A) (HBB: c.217_218insA) (prevalence 0.70%, 0.68%, and 0.2%, respectively). Based on mutation frequencies calculated in this study, estimates of 5021 babies in Vietnam are affected with clinically severe thalassemia annually. Our data suggest a higher thalassemia carrier frequency in Vietnam than previously reported. We established that combining NGS with gap-PCR creates an effective large-scale thalassemia screening method that can detect a broad range of mutations.

Detection of maternal carriers of common α-thalassemia deletions from cell-free DNA.

α-Thalassemia is a common inherited blood disorder manifested mainly by the deletions of α-globin genes. In geographical areas with high carrier frequencies, screening of α-thalassemia carrier state is therefore of vital importance. This study presents a novel method for identifying female carriers of common α-thalassemia deletions using samples routinely taken for non-invasive prenatal tests for screening of fetal chromosomal aneuploidies. A total of 68,885 Vietnamese pregnant women were recruited and α-thalassemia statuses were determined by gap-PCR, revealing 5344 women (7.76%) carried deletions including αα/--SEA (4.066%), αα/-α3.7 (2.934%), αα/-α4.2 (0.656%), and rare genotypes (0.102%). A two-stage model was built to predict these α-thalassemia deletions from targeted sequencing of the HBA gene cluster on maternal cfDNA. Our method achieved F1-scores of 97.14-99.55% for detecting the three common genotypes and 94.74% for detecting rare genotypes (-α3.7/-α4.2, αα/--THAI, -α3.7/--SEA, -α4.2/--SEA). Additionally, the positive predictive values were 100.00% for αα/αα, 99.29% for αα/--SEA, 94.87% for αα/-α3.7, and 96.51% for αα/-α4.2; and the negative predictive values were 97.63%, 99.99%, 99.99%, and 100.00%, respectively. As NIPT is increasingly adopted for pregnant women, utilizing cfDNA from NIPT to detect maternal carriers of common α-thalassemia deletions will be cost-effective and expand the benefits of NIPT.

Hereditary multiple exostoses: A case report and literature review.

Osteochondroma is the most common bone tumor representing 20%-50% of all benign bone tumors and 10%-15% of all bone tumors. Osteochondroma has similar radiological appearance in both solitary and multiple forms; the latter is an autosomal dominant disorder termed hereditary multiple exostoses. Associated complications of osteochondroma include deformity, fracture, neurovascular compromise, bursa formation, and malignant transformation. Measurement of the cartilage cap thickness is an important index suggesting secondary malignancy of osteochondroma. The upper limit of cap thickness after skeletal maturation is 1.5 cm which can be reliably measured on ultrasound or magnetic resonance imaging. Hereditary multiple exostoses are linked to the mutations of different exostoses genes located on chromosome 8, 11, and 19. We reported cases of two siblings presented with multiple osteochondromas managed by surgical excision. We evaluated their clinical and radiological presentation, genetic correlations and compared with the literature.

Massively parallel sequencing uncovered disease-associated variant spectra of glucose-6-phosphate dehydrogenase deficiency, phenylketonuria and galactosemia in Vietnamese pregnant women.

BACKGROUND: Several inherited metabolic diseases are underreported in Vietnam, namely glucose-6-phosphate dehydrogenase deficiency (G6PDd), phenylketonuria (PKU) and galactosemia (GAL). Whilst massively parallel sequencing (MPS) allows researchers to screen several loci simultaneously for pathogenic variants, no screening programme uses MPS to uncover the variant spectra of these diseases in the Vietnamese population. METHODS: Pregnant women (mean age of 32) from across Vietnam attending routine prenatal health checks agreed to participate and had their blood drawn. MPS was used to detect variants in their G6PD, PAH and GALT genes. RESULTS: Of 3259 women screened across Vietnam, 450 (13.8%) carried disease-associated variants for G6PD, PAH and GALT. The prevalence of carriers was 8.9% (291 of 3259) in G6PD and 4.6% (152 of 3259) in PKU, whilst GAL was low at 0.2% (7 of 3259). Two GALT variants, c.593 T > C and c.1034C > A, have rarely been reported. CONCLUSION: This study highlights the need for routine carrier screening, where women give blood whilst receiving routine prenatal care, in Vietnam. The use of MPS is suitable for screening multiple variants, allowing for identifying rare pathogenic variants. The data from our study will inform policymakers in constructing cost-effective genetic metabolic carrier screening programmes.

An Extremely Rare SRD5A2 Gene c.485A>C Mutation in a Compound Heterozygous Newborn with Disorders of Sex Development First Identified in Vietnam.

SRD5A2 (steroid 5-alpha-reductase 2) mutation, which impairs 5α-reductase-2 enzyme activity, is among the causes of 46,XY disorders of sex development (DSD). Here, we report a rare pathogenic mutation NM_000348.4:c.485A>C (NP_000339.2:p.His162Pro) of SRD5A2 gene in a compound heterozygous state first identified in a Vietnamese newborn with 5α-reductase-2 enzyme deficiency. We also first submitted this rare mutation to ClinVar database (VCV000973099.1). The patient presented with hyperpigmented labia-majora-like bifid scrotum, clitoris-like phallus, perineoscrotal hypospadias, and blind-ending vagina. The other mutation NM_000348.4:c.680G>A (NP_000339.2:p.Arg227Gln) was reported previously. This compound heterozygous mutation was first detected by next-generation sequencing. By Sanger sequencing, we confirmed that the c.485A>C mutation was maternal inherited, whereas the c.680G>A mutation was paternal inherited. Up to date, this is the first report of this rare compound heterozygous state of SRD5A2 c.485A>C and c.680G>A mutations in patients with 46,XY DSD generally as well as in Vietnamese population particularly and is also the second report in the world carrying the pathogenic mutation NM_000348.4:c.485A>C (NP_000339.2:p.His162Pro). Our finding has enriched the understanding of the spectrum of SRD5A2 variants and phenotypic correlation in Asian patients with 46,XY DSD.

The MinION as a cost-effective technology for diagnostic screening of the SCN1A gene in epilepsy patients.

The MinION is a portable DNA sequencer that allows real time sequencing at low capital cost investment. We assessed accuracy and cost-effectivess of the MinION for genetic diagnostic testing of known SCN1A mutations that cause Dravet Syndrome (DS). DNA samples (n = 7) from DS patients previously shown to carry SCN1A mutations via Ion Torrent and Sanger sequencing were sequenced using the MinION. SCN1A amplicons for 8 exons were sequenced using the MinION with 1D chemistry on an R9.4 flow cell. All known missense mutations were detected in all samples showing 100 % concordance with results from other methods. However, the MinION failed to detect the insertions/deletions (INDELs) present in these patients. Nevertheless, these results indicate that MinION is a cost-effective platform for use as an initial screening step in the detection of nucleotide substitution mutations in in SCN1A, especially in under-resourced laboratories or hospitals. Further improvements are required to reliably detect INDELS in this gene.

De novo c.2455C>T mutation of NPR2 gene in a fetus with shortened long bones and a ventricular septal defect conceived by a mother with a fragile site at 16q22.1 and a father with a rare heterochromatic variant of chromosome 4 from Vietnam.

BACKGROUND: A heterozygous natriuretic peptide receptor 2 (NPR2) gene c.2455C>T mutation was identified as a cause of familial idiopathic short stature (ISS). Only two cases with this mutation were reported previously, and the probands with ISS had no organ system defects. METHODS: Next-generation sequencing (NGS) was performed on an amniotic fluid DNA sample of a fetus with shortened long bones and a small ventricular septal defect detected by an obstetric ultrasound examination. The pathogenic variant of the fetus was confirmed by Sanger sequencing. Sanger sequencing, G-banded, and C-banded karyotyping of the fetus's parents were subsequently performed. RESULTS: A de novo NPR2 gene c.2455C>T, p.(Arg819Cys) mutation was identified in the fetus. No microdeletion or microduplication was identified in the fetus by copy number variation sequencing with a maximum resolution of 400 kb. The two previous miscarriages experienced by the fetus's parents were interpreted as a result of chromosomal aberrations, including a maternal fragile site at 16q22.1 and a rare paternal variant involving in a large G-band-positive and C-band-positive block of paracentric heterochromatin of chromosome 4p. CONCLUSION: This report provides clinical signs of a de novo heterozygous NPR2 gene c.2455C>T mutation in the fetus and shows paternal chromosomal aberrations causing repeated pregnancy loss.

MBD5-related intellectual disability in a Vietnamese child.

The disruption of methyl-binding domain protein 5 (MBD5) gene has been determined as a significant cause of a group of disorders known as MBD5-associated neurodevelopmental disorder. Here, we report a novel pathogenic mutation, NM_001378120.1 (MBD5): c.217-1G>C, occurring at the acceptor splicing site of intron 6 of the MBD5 gene identified in a Vietnamese child with intellectual disability, autistic-like behaviors, and seizure. Phenotypic manifestations in this patient are highlighted with neurodevelopmental impairments whereas his facial dysmorphism is unremarkable. Our finding has enriched the understanding of the spectrum of MBD5 variants, a critical database for diagnosis, genetic counseling, and management of the patients with neurological diseases.

An experience in prenatal diagnosis via QF-PCR of a female child with a 9.9 Mb pure deletion at 18p11.32-11.22.

Quantitative Fluorescent - Polymerase Chain Reaction (QF-PCR) is a rapid prenatal diagnosis test for 21, 18, 13 and sex chromosomal aneuploidy detection. However, it could not detect partial trisomy or partial monosomy of those chromosomes. Here, we report a 19-month-old Vietnamese female with a 9.9 Mb pure deletion of chromosome 18 at 18p11.32-11.22 confirmed by next generation sequencing. The patient was short statured with facial dysmorphic features as well as motor skill and speech delays. First trimester screening showed high risk of trisomy 21 with only increased nuchal translucency (NT 3.9 mm) by ultrasound as an indication. Prenatal diagnosis by QF-PCR from amniotic DNA revealed normal disomy. Noticeably, two short tandem repeat (STR) markers D18S391 and D18S976 located on 18p exhibited uninformative patterns (one peak). Thus, our case suggested that the combination of both D18S391 and D18S976 markers with uninformative patterns in QF-PCR for prenatal diagnosis and increased NT in the first trimester ultrasound may be a significant indication of 18p monosomy.

High rates of clarithromycin and levofloxacin resistance of Helicobacter pylori in patients with chronic gastritis in the south east area of Vietnam.

BACKGROUND: The increasing rates of clarithromycin (CLR)- and levofloxacin (LVX)-resistant Helicobacter pylori are the main causes of the considerable decrease in the eradication rates of triple therapy and LVX-based regimens. The aims of this study were to determine the rates of CLR- and LVX-resistant H. pylori by the Epsilometer test and to assess the risk factors for this antibiotic resistance among patients with chronic gastritis in the south east area of Vietnam. METHODS: Gastric biopsy specimens were obtained from 153 patients with H. pylori-positive chronic gastritis for use in culture and in the Epsilometer test to determine CLR and LVX susceptibilities. RESULTS: The rates of H. pylori resistance to CLR and LVX were 72.6% and 40.5%, respectively. Dual-resistant H. pylori (to both CLR and LVX) accounted for 30.7% of patients. The rates of high-level resistance to CLR and LVX were 18.9% and 83.9%, respectively. Multivariate analysis showed that age older than 30 years (odds ratio [OR] = 3.80, 95% confidence interval [CI] 1.61-8.97) and history of H. pylori treatment (OR = 8.72, 95% CI 1.90-39.91) were independent risk factors for CLR resistance, whereas only age older than 35 years (OR = 2.42, 95% CI 1.23-4.76) was an independent risk factor for LVX resistance. CONCLUSIONS: These results revealed high rates of resistance of H. pylori to CLR and LVX in patients with chronic gastritis in the south east area of Vietnam. This suggests that CLR-based triple therapy should not be used for the eradication treatment of H. pylori, and LVX susceptibility testing of H. pylori strains should be performed before choosing alternative regimens.

Association of TP53 gene codon 72 polymorphism with Helicobacter pylori-positive non-cardia gastric cancer in Vietnam.

INTRODUCTION: This research aimed to determine the association of the combination of H. pylori infection and TP53 codon 72 polymorphism with non-cardia gastric cancer (GC) in Vietnam. METHODOLOGY: A total of 164 patients with non-cardia GC and 164 patients with peptic ulcer disease or functional dyspepsia in controls matched by sex and age were enrolled. H. pylori infection was diagnosed by rapid urease test and polymerase chain reaction (PCR). The cagA gene-positivity and vacA sm subtypes were determined by multiplex PCR. Genotypes of TP53 codon 72 polymorphism were determined by PCR-restriction fragment length polymorphism. RESULTS: The prevalence of H. pylori infection in GC and control group were 61.6% and 55.4%, respectively. The rates of cagA-positive strains in the two H. pylori-positive groups were 80.2% and 71.4%, respectively. There was no statistically significant difference in TP53 codon 72 genotype distribution between GC group (frequencies of Arg/Arg, Arg/Pro and Pro/Pro genotypes were 31.1%, 43.3% and 25.6%, respectively) and controls (29.3%, 52.4% and 18.3%, respectively), p = 0.172. The significant difference in genotype distribution was observed in recessive model (Pro/Pro vs Arg/Arg + Arg/Pro) when stratifying by H. pylori infection (OR = 2.02, 95% CI 1.03-3.96, p = 0.041) and by cagA-positivity (OR = 2.33, 95% CI 1.07-5.07, p = 0.032). CONCLUSIONS: This study suggests a synergistic interaction between H. pylori infection, especially cagA-positive H. pylori, and Pro/Pro genotype of TP53 codon 72 polymorphism might play a significant role in the pathogenesis of GC in the Vietnamese population.

Characterisation of point mutations in domain V of the 23S rRNA gene of clinical Helicobacter pylori strains and clarithromycin-resistant phenotype in central Vietnam.

OBJECTIVES: The prevalence of clarithromycin (CLR)-resistant Helicobacter pylori is increasing worldwide, including in Vietnam. The aims of this study were to determine point mutations in the 23S rRNA domain V of clinical H. pylori strains in central Vietnam, to estimate the prevalence of phenotypic CLR resistance and to assess the association between 23S rRNA domain V genotype and CLR-resistant phenotype. METHODS: Sequencing of the 23S rRNA domain V of H. pylori strains from gastric biopsy specimens was performed for 185 patients with H. pylori-positive chronic gastritis, of which 104 samples were subjected to susceptibility testing to determine CLR resistance. RESULTS: A total of 24 types of point mutation were detected. A2143G and A2142G mutations were observed in 40.5% and 4.3%, respectively. New point mutations were detected (C2041T, C2083T, C2191T, G2220A, G2225A, G2240A, C2273T, T2276C, G2287A, C2399T, A2445G and C2622T). 23S rRNA domain V genotypes were diversified, with combinations of two or more point mutations as well as single point mutations. The rate of phenotypic CLR resistance was 53.8%, increasing from 40.4% in 2012-2014 to 70.2% in 2015-2017 (P=0.0045). A2143G and A2142G accounted for 89.3% of phenotypically CLR-resistant H. pylori isolates. CONCLUSIONS: A diversity of point mutations in the 23S rRNA domain V was observed in clinical H. pylori isolates. The rate of phenotypically CLR-resistant H. pylori is significantly increasing in central Vietnam. Further research is necessary to clarify the role of the combination of 23S rRNA domain V mutations in the molecular mechanism of CLR resistance.

Helicobacter pylori 23S rRNA gene mutations associated with clarithromycin resistance in chronic gastritis in Vietnam.

INTRODUCTION: Data about the prevalence of the A2142C, A2142G, and A2143G mutations in 23S rRNA gene is still limited. The aim of this study was to determine the prevalence of these mutations in 23S rRNA gene of H. pylori vietnamese strains. METHODOLOGY: One hundred and sixty-nine patients with H. pylori-positive chronic gastritis were examined. H. pylori was detected by rapid urease test and Polymerase chain reaction (PCR). Total DNA was extracted from gastric biopsy specimens. A2142C, A2142G, and A2143G mutations were detected by DNA sequencing and PCR-restriction fragment length polymorphism (PCR-RFLP). RESULTS: A2143G mutation was detected in 36.1% of samples, A2142G mutation in 3.6%, while A2142C mutation was not found in any case. The mixture of wild-type and mutation strains was found in 50% of specimens with A2142G, in 23% of specimens with A2143G mutation. There was no association of 23S rRNA gene point mutations with gender or age. However, an association between the heterogeneity of mutation and age was evidenced, with mean age of the group of pure A2143G higher than the group of wild-type/A2143G mixture, and rate of the wild-type/A2143G mixture higher in patients under 40 years of age. CONCLUSION: A2143G mutation was prominent, while A2142C mutation was not found in the 23S rRNA gene. PCR-RFLP has revealed a reliable assay allowing a rapid and cost-effective detection of clarithromycin-resistant strains. This is useful in countries as Vietnam with high prevalence of clarithromycin-resistance before choosing optimal therapy for H. pylori eradication.