L13- Helicobacter Pylori Flashcards

Question

Urea breath Test

Answer 1

- Using Urea solution with labelled carbon isotopes (i.e. radioactive ¹⁴C or non-radioactive ¹³C) - Subject will ingest the urea solution. HP in gastric mucosa will convert the ingested urea to ammonia, water and CO₂. Thus the expired CO₂ will contain labelled carbon if HP is present. - ¹⁴C test not recommended for children and pregnant women due to radioactivity - Most of the current urea breath tests use ¹³C.

Answer 2

**Biopsy required:** - Rapid Urea Test - Bacteriology (culture) - Histopathological diagnosis - *PCR* **Biopsy not required:** - Urea breath test - Serology - Stool antogen detection test - *PCR*

Answer 3

- To cure peptic ulcer disease and reduce the lifetime risk of gastric cancer.

Answer 4

**Clearance** = absence of detectable organisms immediately after stopping therapy. **Eradication** = absence of detectable organisms ≥4 weeks after stopping therapy.

Answer 5

In vitro antibiotic sensitivity ≠ clinical efficacy, because: - pH stability of antibiotic in acidic gastric environment - Penetration ability of antibiotic into the mucus gel coat where HP is located

Answer 6

**1) Urea breath test**: the preferred method for assessing the success of therapy. **2) A laboratory-based, validated, stool antigen detection assay -** Immunochromatigraphic Assay (ICA) 3) Serology not useful - as titre only decreases after 6-12 months

Answer 7

- Generally less common in developed countries. - Ranges from 2.67% to 13%.

Answer 8

Mneumonic: **_T_**ummy **_A_**nd **_C_**ardia **_B_**etter **_R_**ight **_N**_ow _**P_**lease **1) Tetracycline** **2) Amoxillin** **3) Clarithromycin** **4) Bismuth compounds** - Pepto-Bismol (bismuth subsalicylate) - DeNol (tripotassium dicitrato bismuthate) - Pylera (bismuth-metronidazole-tetracycline) **5) Ranitidine bismuth citrate** **6) Nitroimidazoles** - metronidazole - tinidazole **7) PPI (proton-pump inhibitors)** - Omeprazole - Esomeprazole - Lansoprazole (- Pantoprazole - Rabeprazole)

Answer 9

- Stable in acidic pH - High topical concentration - Contraindicated in children (\<8 years) and pregnant women - Occurrence of resistance rare.

Answer 10

- ß-lactam antibiotic - Acid-stable - more active at neutral pH - Occurrence of resistance rare. **Side effects:** - Hypersensitivity reactions (rash, fever, anaphylactic shock) - Gastrointestinal disturbance (e.g. diarrhoea, because it alter the bacterial flora in the gut)

Answer 11

- A macrolide antibiotic - Highly active on H. pylori. - More acid-stable and more active than erythromycin. - A key component in many treatment regimens. - growing prevalence of clarithromycin resistance - compromising success rates of clarithromycin-containing regimens in recent years **Side effects:** - Hypersensitivity reactions (rash, fever, anaphylactic shock) - Gastrointestinal disturbance (e.g. diarrhoea) because it alter the bacterial flora in the gut

Answer 12

- A topical antimicrobial. - Disrupts integrity of bacterial cell wall. Prevents adhesion to gastric epithelium. - Inhibits bacterial urease, phospholipase, and protease - Two commercially available preparations: i) Bismuth subsalicylate (Pepto-Bismol) ii) Tripotassium dicitrato bismuthate (DeNol) - Newer formulation consisting of bismuth subcitrate potassium, metronidazole, and tetracycline in the same capsule: i) Bismuth- metronidazole- tetracycline (Pylera)

Answer 13

- Formed by reaction of ranitidine with bismuth citrate. - Higher solubility and antibacterial activity than an equimolar admixture of ranitidine and bismuth citrate.

Answer 14

- e.g. metronidazole, tinidazole - Highly active against H. pylori. - Well absorbed but actively secreted into gastric juice and saliva - pH-independent antibacterial activity. - Prevalence of resistance in Hong Kong: overall 29–39% in two local studies. Up to 71.4% in some years.

Answer 15

- e.g. Omeprazole, esomeprazole, Lansoprazole, (Pantoprazole, Rabeprazole) - Some direct action on H. pylori. - Optimizes intragastric pH for other antibiotics. - Suppresses but does not eradicate the organism when given alone in vivo

Answer 16

1) Triple therapy (PPI-based) 2) Triple therapy (bismuth-based) 3) Ranitidine bismuth citrate-based therapy 4) Quadruple therapy and second- / third-line treatment 5) Sequential therapy

Answer 17

**PPI + clarithromycin + amoxicillin** or **metronidazole** - Duration of treatment: 10–14 days (higher efficacy than 7 days). - Lower eradication rates in the presence of antibiotic resistance (especially clarithromycin)

Answer 18

**Bismuth + metronidazole + amoxicillin** or **tetracycline** - Most failures due to metronidazole resistance. - Metronidazole resistance: substitute with **clarithromycin** or **azithromycin**.

Answer 19

**1) Ranitidine bismuth citrate + clarithromycin.** **2) Ranitidine bismuth citrate + clarithromycin + amoxicillin.** **3) Ranitidine bismuth citrate + clarithromycin + metronidazole.** [Ranitidine bismuth citrate may not be available in some countries. Not registered in Hong Kong as of February 2014]

Answer 20

**1)** PPI + bismuth + two antibiotics (e.g. tetracycline + metronidazole or amoxicillin + clarithromycin). **2)** PPI + three antibiotics (e.g. amoxicillin + nitroimidazole + clarithromycin). **3)** Levofloxacin- or moxifloxacin-based regimens (when there is resistance to other antibiotics) [Antibiotic susceptibility testing is essential for patients who failed the initial standard regimens]

Answer 21

5 days of PPI + amoxicillin; followed by 5 days of PPI + clarithromycin + nitroimidazole.

Answer 22

consider: 1) efficacy 2) side effects 3) cost 4) compliance 5) antibiotic resistance 6) adverse drug interaction.

Answer 23

Guidelines exist on the indications for treatment, e.g. _the Maastricht IV / Florence Consensus Report_. Main indications include the following patients with a positive test for H. pylori: 1) Peptic Ulcer Disease (Duodenal ulcer, gastric ulcer) 2) Gastric MALT lymphoma. 3) Non-ulcer dyspepsia. 4) Chronic users of NSAIDs