From UPSC perspective, the following things are important :
Prelims level : H. pylori
Mains level : NA
- Indian researchers have developed a groundbreaking two-step PCR-based assay for detecting Helicobacter pylori (H. pylori) infection, determining clarithromycin resistance, and distinguishing drug-sensitive strains.
- This molecular diagnostic tool reduces the detection time from weeks to just six-seven hours and exhibits remarkable accuracy, boasting 100% sensitivity and specificity.
About H. Pylori Detection
- Helicobacter pylori, often abbreviated as H. pylori, is a type of bacteria that can infect the stomach and the upper part of the small intestine.
- It is a common bacterial infection associated with various gastrointestinal conditions, including gastritis (inflammation of the stomach lining) and peptic ulcers (sores or lesions in the lining of the stomach or the duodenum, which is the first part of the small intestine).
Why discuss this?
- Increasing Resistance: India faces a growing challenge of clarithromycin-resistant H. pylori strains, resulting in decreased treatment efficacy.
- Asymptomatic Infections: While most H. pylori infections are asymptomatic, 10–15% of cases lead to peptic ulcer disorders or stomach cancer.
- Prevalence in India: H. pylori infections affect 60-70% of the Indian population, acquired in childhood and persisting if not treated.
- Gastric Cancer Risk: H. pylori infection is a significant risk factor for gastric cancer.
Understanding Drug Resistance Mechanism in H. Pylori
- Genome Sequencing: Researchers identified a point mutation (A to G mutation at position 2143) in the 23S ribosomal RNA (rRNA) gene as the cause of clarithromycin resistance.
- Confirmation: They isolated and transferred the 617 base pairs containing the mutation to drug-sensitive bacteria, which became resistant, confirming the mutation’s role.
- Published Findings: The study’s results were published in the journal Gut Pathogens.
- Exploring Binding Affinity: Bioinformatics analysis revealed that drug-resistant strains had weaker binding affinity to clarithromycin compared to drug-sensitive strains.
- Impact of Weak Binding: Weaker binding limits the drug’s penetration into bacteria, rendering it ineffective against resistant strains.
Development of the PCR-Based Assay
- Biopsy Samples: The DNA template used for the assay was prepared by amplifying a small segment containing the point mutation directly from biopsy samples.
- Validation: DNA templates from cultured bacteria were compared with those from biopsy samples to validate their accuracy.
- Two-Step PCR: The assay employs a two-step PCR approach to detect H. pylori infection and differentiate resistant from sensitive isolates.
- Allele-Specific Primers: Resistant-specific and sensitive-specific primers exploit the point mutation for selective amplification.
- High Accuracy: Evaluation against conventional methods and sequencing analysis demonstrated 100% sensitivity and specificity.