Detection of Helicobacter pylori in gastric mucosa of patients with gastroduodenal diseases by PCR-restriction analysis using the RNA polymerase gene (rpoB)

Application of PCR and Microscopy to Detect Helicobacter pylori in Gastric Biopsy Specimen among Acid Peptic Disorders at Tertiary Care Centre in Eastern Nepal

BACKGROUND

Helicobacter pylori infection is most prevalent in developing countries. It is an etiological agent of peptic ulcer, gastric adenocarcinoma, and mucosal-associated lymphoid tissue (MALT) lymphoma. Despite the development of different assays to confirm H. pylori infection, the diagnosis of infection is challenged by precision of the applied assay. Hence, the aim of this study was to understand the diagnostic accuracy of PCR and microscopy to detect the H. pylori in the gastric antrum biopsy specimen from gastric disorder patients.

METHODS

A total of 52 patients with gastric disorders underwent upper gastrointestinal endoscopy with biopsy. The H. pylori infection in gastric biopsies was identified after examination by microscopy and 23S rRNA specific PCR. The agreement between two test results were analysed by McNemar's test and Kappa coefficient.

RESULT

H. pylori infection was confirmed in 9 (17.30%) patients by both assays, 6.25% in antral gastritis, 22.22% in gastric ulcer, 100% in gastric ulcer with duodenitis, 50% in gastric ulcer with duodenal ulcer, and 33.33% in severe erosive duodenitis with antral gastritis. Out of nine H. pylori infection confirmed patients, 3 patients were confirmed by microscopy and 8 patients by PCR. In case of two patients, both microscopy and PCR assay confirmed the H. pylori infection. The agreement between two test results was 86.54% and disagreed by 13.46% (p value > 0.05).

CONCLUSION

We found that PCR assay to detect H. pylori is more sensitive than microscopy. However, we advocate for the combination of both assays to increase the strength of diagnostic accuracy due to the absence of the gold standard assay for H. pylori infection.

An investigation of Panax ginseng Meyer growth promotion and the biocontrol potential of antagonistic bacteria against ginseng black spot

Background

Ginseng black spot disease resulting from Alternaria panax Whuetz is a common soil-borne disease, with an annual incidence rate higher than 20–30%. In this study, the bacterial strains with good antagonistic effect against A. panax are screened.

Methods

A total of 285 bacterial strains isolated from ginseng rhizosphere soils were screened using the Kirby–Bauer disk diffusion method and the Oxford cup plate assay. We analyzed the antifungal spectrum of SZ-22 by confronting incubation. To evaluate the efficacy of biocontrol against ginseng black spot and for growth promotion by SZ-22, we performed pot experiments in a plastic greenhouse. Taxonomic position of SZ-22 was identified using morphology, physiological, and biochemical characteristics, 16S ribosomal DNA, and gyrB sequences.

Results

SZ-22 (which was identified as Brevundimonas terrae) showed the strongest inhibition rate against A. panax, which showed 83.70% inhibition, and it also provided broad-spectrum antifungal effects. The inhibition efficacies of the SZ-22 bacterial suspension against ginseng black spot reached 82.47% inhibition, which is significantly higher than that of the 25% suspension concentrate azoxystrobin fungicide treatment (p < 0.05). Moreover, the SZ-22 bacterial suspension also caused ginseng plant growth promotion as well as root enhancement.

Conclusion

Although the results of the outdoor pot-culture method were influenced by the pathogen inoculum density, the cropping history of the field site, and the weather conditions, B. terrae SZ-22 controlled ginseng black spot and promoted ginseng growth successfully. This study provides resource for the biocontrol of ginseng black spot.

Bacillus amyloliquefaciens: a mosquitocidal bacterium from mangrove forests of Andaman & Nicobar islands, India

Samples collected from the mangrove forests of Andaman & Nicobar islands yielded a mosquitocidal bacterium, whose extracellular metabolite(s) exhibited mosquito larvicidal and pupicidal activity. The bacterium was isolated using standard microbiological methods and identified using classical biochemical tests and rpoB gene sequences. The mosquitocidal bacterium was identified as Bacillus amyloliquefaciens. Mosquitocidal metabolite(s) was separated from the culture supernatant of the bacterium and its efficacy against the larval and pupal stages of different species of mosquitoes was determined in terms of LC(50) and LC(90). Mosquito larvicidal activity in terms of LC(50) against Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti was respectively, 26.4μg, 22.2μg and 20.5μg/ml and its pupicidal activity was 4.4μg, 8.2μg and 14.5μg/ml respectively. The mosquitocidal metabolite(s) was found to be a biosurfactant. This is the first report of the mosquitocidal activity of B. amyloliquefaciens and it is a new weapon which can be added to the array of microbial agents for use against mosquitoes.

PCR-based genotyping of Helicobacter pylori of Gambian children and adults directly from biopsy specimens and bacterial cultures

Background

Helicobacter pylori is an important agent of gastroduodenal disease in Africa and throughout the world. We sought to determine an optimum method for genotyping H. pylori strains from children and adults in The Gambia, West Africa.

Results

Virulence genes were amplified in 127 of 190 cases tested (121 adults and 6 children); each of 60 bacterial cultures, and 116 from DNA extracted directly from biopsies. The proportion of biopsies that were cagA+, the ratio of vacAs1/s2, and vacAm1/m2, and the proportion of mixed strain populations in individual subjects changed with age. Strains lacking virulence cagA and vacA genes and with apparently homogeneous (one predominant strain) infections were more common among infants than adults.

Conclusions

In order to detect the range of bacterial genotypes harbored by individual patients, direct PCR proved slightly superior to isolation of H. pylori by biopsy culture, but the techniques were complementary, and the combination of both culture and direct PCR produced the most complete picture. The seemingly higher virulence of strains from adult than infant infections in The Gambia merits further analysis.

Molecular Characterization of the 16S rRNA Gene of Helicobacter fennelliae Isolated from Stools and Blood Cultures from Paediatric Patients in South Africa

Forty strains of H. fennelliae collected from paediatric blood and stool samples over an 18 year period at a children's hospital in Cape Town, South Africa, were amplified by PCR of the 16S rRNA. Two distinct genotypes of H. fennelliae were identified based on the phylogenetic analysis. This was confirmed by sequencing a portion of the beta subunit of the RNA polymerase (rpoB) gene. All isolates from South Africa clustered with a proposed novel Helicobacter strain (accession number AF237612) isolated in Australia, while three H. fennelliae type strains from the northern hemisphere, NCTC 11612, LMG 7546 and CCUG 18820, formed a separate branch. A large (355bp) highly conserved intervening sequence (IVS) in the 16S rRNA was found in all isolates. Predicted secondary structures of the IVS from the 16S rRNA and 23S rRNA were characterised by a primary stem structure formed by base pairing of the 3′ and 5′ ends and internal loops and stems. This phylogenetic analysis is the largest undertaken of H. fennelliae. The South African H. fennelliae isolates are closely related to an Australian isolate previously reported to be a possible novel species of Helicobacter. This study suggests that the latter is strain of H. fennelliae.

Differentiation of Bifidobacterium species using partial RNA polymerase {beta}-subunit (rpoB) gene sequences

Partial RNA polymerase β-subunit gene (rpoB) sequences (315 bp) were determined and used to differentiate the type strains of 23 species of the genus Bifidobacterium. The sequences were compared with those of the partial hsp60 (604 bp) and 16S rRNA genes (1475 or 1495 bp). The rpoB gene sequences showed nucleotide sequence similarities ranging from 84.1 % to 99.0 %, while the similarities of the hsp60 sequences ranged from 78.5 % to 99.7 % and the 16S rRNA gene sequence similarities ranged from 89.4 % to 99.2 %. The phylogenetic trees constructed from the sequences of these three genes showed similar clustering patterns, with the exception of several species. The Bifidobacterium catenulatum-Bifidobacterium pseudocatenulatum, Bifidobacterium pseudolongum subsp. pseudolongum-Bifidobacterium pseudolongum subsp. globosum and Bifidobacterium gallinarum-Bifidobacterium pullorum-Bifidobacterium saeculare groups were more clearly differentiated in the partial rpoB and hsp60 gene sequence trees than they were in the 16S rRNA gene tree. Based on sequence similarities and tree topologies, the newly determined rpoB gene sequences are suitable molecular markers for the differentiation of species of the genus Bifidobacterium and support various other molecular tools used to determine the relationships among species of this genus.

Quantitative detection of Helicobacter pylori in water samples by real-time PCR amplification of the cag pathogenicity island gene, cagE

AIMS

A new real-time PCR assay that simultaneously amplifies a 102-bp fragment of the cagE gene from Helicobacter pylori and a new internal positive control containing a specific sequence of the gyrB gene from Aeromonas hydrophila, was developed and validated for the detection of H. pylori in environmental samples.

METHODS AND RESULTS

The specificity, limits of detection and quantification, repeatability, reproducibility, and accuracy of the method were calculated. The resulting values confirmed the applicability of the method for the quantitative detection of H. pylori. The feasibility of the method was also evaluated by testing 13 pyloric antrum-positive biopsies and 69 water samples, including potable (10), surface (19) and wastewater (40) matrices. The results showed that all the biopsies and 3 of the 40 wastewater samples analysed were positive.

CONCLUSIONS

This real-time PCR method provides a sensitive, specific, and accurate method for the rapid quantification of H. pylori in environmental samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

The PCR diagnostic system proposed in this work, provides a suitable tool for the quantitative detection of H. pylori in environmental samples and can be useful for verifying the role of water as a potential route of its transmission.

Direct detection and analysis of vacA genotypes and cagA gene of Helicobacter pylori from gastric biopsies by a novel multiplex polymerase chain reaction assay

Several tests/methods for the infection, detection, and genotyping of Helicobacter pylori have been developed in the past; all these differ in specificity and sensitivity and thereby could not be routinely used in clinical study especially in resource-poor developing countries. In the present study, a novel method based on multiplex polymerase chain reaction (PCR) assay was developed to detect H. pylori in patients suffering from gastrointestinal diseases. This method does not require steps of sonication, boiling, or centrifugation for obtaining DNA from biopsy samples, which are otherwise prerequisite in detecting H. pylori by PCR assay. Two hundred seventy-six patients were examined, of which 182 cases (excluding 36 patients having multiple H. pylori strain infection and 8 showing amplification of 16S rDNA only) were H. pylori positive. The dominant vacA genotype was s1 and m1 being present in 168 (92.3%) and 106 (58.2%) patients, respectively, followed by m2 (41.7%), and the lowest being s2 (7.7%). Detection of H. pylori by this method seems rapid, simpler, and suitable for both types 1 and 2 bacteria. Furthermore, genotyping of vacA and cagA genes could also be routinely performed in a large number of patients for diagnostic purposes.

Expression of Helicobacter pylori virulence factors and associated expression profiles of inflammatory genes in the human gastric mucosa

Helicobacter pylori virulence factors have been suggested to be important in determining the outcome of infection. The H. pylori adhesion protein BabA2 is thought to play a crucial role in bacterial colonization and in induction of severe gastric inflammation, particularly in combination with expression of CagA and VacA. However, the influence of these virulence factors on the pathogenesis of H. pylori infection is still poorly understood. To address this question, the inflammatory gene expression profiles for two groups of patients infected with triple-negative strains (lacking expression of cagA, babA2, and vacAs1 but expressing vacAs2) and triple-positive strains (expressing cagA, vacAs1, and babA2 but lacking expression of vacAs2) were investigated. The gene expression patterns in the antrum gastric mucosa from patients infected with different H. pylori strains were very similar, and no differentially expressed genes could be identified by pairwise comparisons. Our data thus suggest that there is a lack of correlation between the host inflammatory responses in the gastric mucosa and expression of the babA2, cagA, and vacAs1 genes.

Moraxella bovoculi sp. nov., isolated from calves with infectious bovine keratoconjunctivitis

Eighteen isolates of a Gram-negative coccus (strain 237T) were cultured from the eyes of dairy and beef calves affected with infectious bovine keratoconjunctivitis (IBK; ‘pinkeye’) in northern California, USA, during summer 2002. These isolates had near full-length (1397 bp) 16S rRNA gene sequences that clustered into three groups with 99.9 % sequence similarity. On the basis of 16S rRNA gene sequence, the isolates were most closely associated with Moraxella bovis and Moraxella ovis in clade I of the classical moraxellae. Biochemically, the novel isolates could be distinguished from the other members of the genus Moraxella isolated from animals on the basis of phenylalanine deaminase activity. The results of partial sequence analysis of six housekeeping genes, the 16S–23S rRNA gene interspacer region and partial 23S rRNA gene provide strong support for the inclusion of these isolates in a novel taxon, for which the name Moraxella bovoculi sp. nov. is proposed. The type strain is strain 237T (=ATCC BAA-1259T=CCUG 52049T).

Detection and identification of Mycobacterium tuberculosis in joint biopsy specimens by rpoB PCR cloning and sequencing

Osteoarticular tuberculosis (OAT) is an extrapulmonary tuberculosis and accounts for 1 to 3% of all tuberculosis cases. We used an rpoB PCR-plasmid TA cloning-sequencing method to detect and identify tubercle bacilli in surgical specimens from patients suspected of having OAT. By comparing the similarities of the rpoB sequences determined with those in GenBank, Mycobacterium tuberculosis was detected in 23 of 43 samples. Three of the 23 positive samples had mutations at codon 531, which are commonly observed in rifampin-resistant M. tuberculosis strains. Our results suggest that the rpoB PCR-TA cloning-sequencing method developed, which detects M. tuberculosis and which simultaneously determines its rifampin susceptibility, can also be used efficiently for the diagnosis of OAT.

Alanine-threonine polymorphism of Helicobacter pylori RpoB is correlated with differential induction of interleukin-8 in MKN45 cells

Geographical differences in the genetic diversity of Helicobacter pylori isolates were examined by analyzing rpoB sequences. An extremely high level of allelic diversity among H. pylori strains was found. The rpoB sequences of Asian and non-Asian (North and South American, European, and South African) strains were found to differ. An amino acid polymorphism (alanine and threonine RpoB types) was found at the 497th residue by deduced amino acid analysis. RpoB with a threonine residue (RpoB(Thr)) was uniquely present in East Asian countries, and two-thirds of the H. pylori isolate population in this region was RpoB(Thr); however, this type was rare or absent in Western countries, where RpoB(Ala) predominated. RpoB(Thr) strains induced a much larger amount of interleukin-8, a chemokine that plays an important role in chronic inflammation, than RpoB(Ala) strains in cultured MKN45 cells.

Multiplex PCR assay for rapid detection and genotyping of Helicobacter pylori directly from biopsy specimens

We developed and evaluated a simple, novel multiplex PCR assay for rapid detection of Helicobacter pylori infection and for the determination of vacA and cagA genotypes directly from gastric biopsy specimens. This assay did not require culturing of strains or extraction of DNA from biopsy samples. This multiplex PCR assay would be of particularly great value for laboratories in developing countries.