Direct detection of Helicobacter pylori in biopsy specimens using a high-throughput multiple genetic detection system

A rapid and high-throughput multiplex genetic detection assay for detection, semi-quantification and virulence genotyping of Helicobacter pylori in non-invasive oral samples

Aim

This study established a high-throughput multiplex genetic detection assay (HMGA) for rapid identification, semi-quantification and virulence analysis of Helicobacter pylori directly from the clinical non-invasive oral samples.

Methods

The gastric mucosa and oral samples were collected from 242 patients in Shanghai from 2021 to 2022. All the samples were detected by routine clinical tests for H. pylori and Sanger sequenced for inconsistent results. A new multiplex PCR assay providing results within 4 hours was designed and optimized involving fluorescent dye-labeled specific primers targeted 16S rRNA gene, semi-quantitative gene ureC and 10 virulence genes of H. pylori. Semi-quantification was carried out by simulating the serial 10-fold dilutions of positive oral samples, and the H. pylori loads in different clinical samples were further compared. The mixed plasmids of virulence genes vacA s1, vacA m1 and vacA m2 were used to evaluate the performance on different genotypes. The consistency of 10 virulence genes in gastric mucosa, saliva, mouthwash and dental plaque of H. pylori-positive patients was compared.

Results

The non-invasive HMGA was highly specific for detection of all 12 targets of H. pylori and human internal reference gene β-globin, and the sensitivity to all target genes could reach 10 copies/μL. Compared with routine clinical tests and sequencing, non-invasive HMGA has a high level (>0.98) of sensitivity, specificity, accuracy, PPV, NPV and kappa coefficient for direct detection of H. pylori in oral samples. Moreover, by detecting peak area levels of ureC, it was confirmed that the H. pylori loads in gastric mucosa were significantly higher than those of the three kinds of oral samples (p<0.05). We also found that 45.0% (91/202) of patients had different H. pylori virulence genes in different oral samples. The concordance of positive detection rates of each virulence gene between saliva and gastric mucosa was more than 78% (p<0.05).

Conclusion

The non-invasive HMGA proved to be a reliable method for the rapid H. pylori identification, semi-quantification and detection of 10 virulence genes directly in oral samples, providing a new idea for non-invasive detection of H. pylori.

Generation and identification of a thyroid cancer cell line with stable expression of CCDC67 and luciferase reporter genes

Coiled-coil domain containing 67 (CCDC67) gene is a tumor suppressor gene that exhibits a significant inhibitory effect on a variety of tumors. Our previous study demonstrated that the upregulation of CCDC67 gene in TPC-1 cells inhibited cell proliferation, migration and invasion, and promoted apoptosis in vitro. However, due to the lack of a suitable cell tool, these results were not validated in vivo. In the present study, a thyroid cancer cell line with stable expression of CCDC67 and luciferase reporter genes was generated and identified. Firstly, cDNA clones of the CCDC67 gene were obtained by reverse transcription using a custom-designed primer. The results of subsequent electrophoresis analysis and sequencing revealed that the cDNA clones of CCDC67 gene were obtained successfully, with a length of 1,862 bp. The lentiviral vectors, containing the CCDC67, luciferase reporter and puromycin acetyltransferase genes, were co-transfected with two plasmids that encode lentiviral structural proteins and envelope proteins into 293T cells. Following ultracentrifugation, the titer of lentivirus was determined by ELISA to be 5.0×10⁸ TU/ml. The constructed lentiviral vector was used to transfect TPC-1 thyroid cancer cells, and stabilization was achieved by puromycin screening. The expression of CCDC67 gene, luciferase activity and tumorigenic ability of the generated cell line were detected. Reverse transcription-qPCR results demonstrated that the expression levels of CCDC67 gene in TPC-1 cells following transfection were increased 194,46.782-fold compared with those in the negative control group (P<0.01). A higher fluorescence intensity was detected in the generated cell line, while no detectable fluorescence was observed in untransfected TPC-1 cells. The tumorigenic ability of TPC-1-Luc-Puromycin-CCDC67 cells was verified by bioluminescence imaging and histopathological analysis using a pulmonary metastasis model. These results demonstrated that a thyroid cancer cell line with stable expression of CCDC67 and luciferase reporter genes was generated successfully. The TPC-1-Luc-Puromycin-CCDC67 cell line may be a helpful tool for further research on CCDC67 in vivo.

Differential Helicobacter pylori Plasticity in the Gastric Niche of Subjects at Increased Gastric Cancer Risk

Helicobacter pylori (H. pylori) represents an independent risk factor for Gastric Cancer (GC). First Degree Relatives (FDR) of GC subjects and Autoimmune Gastritis (AG) patients are both at increased risk for GC. H. pylori genetic heterogeneity within the gastric niche of FDR and AG individuals has been little explored. To understand whether they exploit an increased H. pylori stability and virulence, 14 AG, 25 FDR, 39 GC and 13 dyspeptic patients (D) were investigated by a cultural PCR-based approach characterizing single colonies-forming-units. We chose three loci within the Cytotoxin-associated gene-A Pathogenicity Island (CagPAI) (cagA,cagE,virB11), vacA, homA and homB as markers of virulence with reported association to GC. Inflammatory/precancerous lesions were staged according to Sydney System. When compared to D, FDR, similarly to GC patients, were associated to higher atrophy (OR = 6.29; 95% CI:1.23-31.96 in FDR; OR = 7.50; 95% CI:1.67-33.72 in GC) and a lower frequency of mixed infections (OR = 0.16; 95% CI:0.03-0.81 in FDR; OR = 0.10; 95% CI:0.02-0.48 in GC). FDR presented also an increased neutrophil infiltration (OR = 7.19; 95% CI:1.16-44.65). Both FDR and GC carried a higher proportion of CagPAI⁺vacAs1i1mx⁺homB⁺ profiles (OR = 2.71; 95% CI: 1.66-4.41 and OR = 3.43; 95% CI: 2.16-5.44, respectively). Conversely, AG patients presented a lower frequency of subtypes carrying a stable CagPAI and vacAs1i1mx. These results underline different H. pylori plasticity in FDR and AG individuals, and thus, a different host-bacterium interaction capacity that should be considered in the context of eradication therapies.

Antibiotic resistance in Helicobacter pylori

PURPOSE OF REVIEW

Treatment of Helicobacter pylori is difficult nowadays because of its high resistance. The prevalence and mechanism of resistance, the different methods to detect it and the clinical implication of resistance were addressed in several research papers last year.

RECENT FINDINGS

Clarithromycin-resistant H. pylori has been recognized by the WHO as 'high priority', for which new antibiotics are needed. Moreover, the Maastricht consensus recommended, in areas with high resistance, that susceptibility tests should be performed, at least after a treatment failure.

SUMMARY

Metronidazole and clarithromycin resistance rates are alarming although they vary among populations. Tetracycline and amoxicillin-resistance are very low in most countries. H. pylori resistance can be detected by phenotypic or by molecular methods. Different break points may be used when performing an antimicrobial susceptibility test, so comparing resistance among different populations is challenging. Genomic techniques open new possibilities in the diagnosis of H. pylori, and the detection of H. pylori and its antimicrobial resistance in faeces is an interesting approach. Eradication rates are dependent on the susceptibility of the strain to metronidazole and clarithromycin, being lower in patients infected with a resistant strain.

Diagnosis of Helicobacter pylori infection

Important progress is being made in endoscopic methods which allow clinicians to predict the presence of Helicobacter pylori based on characteristics of gastric mucosa and to obtain targeted biopsies. There are also important developments in molecular methods with various techniques derived from standard PCR, applied both on gastric biopsies and stool specimens. Progress is being made in microfluidic systems to get a reliable diagnosis in a very short time. The interest of the ¹³ C urea breath test has been confirmed as well as stool antigen tests. Attempts are being made to find biological markers of premalignant conditions by serology, other than pepsinogens.