A 45-year-old woman has a history of mild epigastric pain, which seems to have gotten worse over the last month. Her pain is most severe several hours after a meal and is somewhat relieved with over-the-counter antacids. The patient denies abnormal tastes in her mouth or radiating pain. She does not take any other over-the-counter medications. She denies bleeding, anemia, or unexplained weight loss, and denies a family history of gastrointestinal malignancy. Which of the following is the best next step in the management of this patient?

Empiric proton pump inhibitor therapy

Upper endoscopy with biopsy of gastric mucosa

A 30-year-old man who recently emigrated from Southeast Asia presents with heartburn and a bad taste in his mouth. He says the symptoms have been present for the last 6 months and are much worse at night. He describes the pain as moderate to severe, burning in character, and localized to the epigastric region. He mentions that 1 month ago, he was tested for Helicobacter pylori back in his country and completed a course of multiple antibiotics, but there has been no improvement in his symptoms. Which of the following is the most likely diagnosis in this patient?

Gastroesophageal reflux disease

Gastric MALT (mucosa-associated lymphoid tissue) lymphoma

A 28-year-old graduate student visits the university health clinic for 3-weeks of epigastric pain that worsens with meals, associated with retrosternal pain, early satiety, and bloating. She denies vomiting blood or blood in her stool. She has been consuming large volumes of caffeinated-drinks and fast-food for a month, as she has been studying for her tests. Her family and personal history are unremarkable with no history of gastrointestinal cancer. Her vital signs are within normal limits. Physical examination is only positive for a mild epigastric tenderness. Which of the following is the most appropriate approach in this case?

Fecal antigen testing for Helicobacter pylori

A 52-year-old man comes to the physician because of a 3-month history of upper abdominal pain and nausea that occurs about 3 hours after eating and at night. These symptoms improve with eating. After eating, he often has a feeling of fullness and bloating. He has had several episodes of dark stools over the past month. He has smoked one pack of cigarettes daily for 40 years and drinks 2 alcoholic beverages daily. He takes no medications. His temperature is 36.4°C (97.5°F), pulse is 80/min, and blood pressure is 110/70 mm Hg. Abdominal examination shows epigastric tenderness with no guarding or rebound. Bowel sounds are normal. Which of the following treatments is most appropriate to prevent further complications of the disease in this patient?

Amoxicillin, clarithromycin, and omeprazole

Intravenous vitamin B12 supplementation

Fundoplication, hiatoplasty, and gastropexy

Distal gastrectomy with gastroduodenostomy

A previously healthy 37-year-old man comes to the physician for the evaluation of an 8-week history of intermittent burning epigastric pain. During this period, he has also felt bloated and uncomfortable after meals. He has not had weight loss or a change in bowel habits. He has no personal or family history of serious illness. He takes no medications. He does not smoke. He drinks 1–3 beers per week. Vital signs are within normal limits. Abdominal examination shows mild epigastric tenderness on palpation without guarding or rebound tenderness. Bowel sounds are normal. The remainder of the examination shows no abnormalities. Which of the following is the most appropriate next step in management?

Helicobacter pylori eradication therapy

Upper gastrointestinal endoscopy

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

Helicobacter pylori for USMLE Step 1: High-Yield Microbiology Lessons

Microbiology - Stomach's Spiral Squatter

Helicobacter pylori attaching to stomach lining

Gram-negative, spiral-shaped rod colonizing the gastric antrum.
Highly motile via flagella; catalase, oxidase, and urease-positive.
- Urease neutralizes stomach acid, enabling survival.
Causes chronic gastritis, peptic ulcers (duodenal > gastric), and is a major risk factor for gastric adenocarcinoma and MALT lymphoma.
Diagnosis: Urea breath test, stool antigen.
Treatment: 📌 Triple therapy (Clarithromycin, Amoxicillin, PPI).

⭐ H. pylori is the first formally recognized bacterial carcinogen.

Pathogenesis & Virulence - Acid-Proofing Antics

Primary Challenge: Survives in the highly acidic (pH 1-2) stomach lumen.
Key Enzyme: Urease
- Abundantly produced, found on the bacterial surface and cytoplasm.
- Catalyzes urea hydrolysis: $Urea + H_2O \rightarrow 2NH_3 + CO_2$.
- Ammonia ($NH_3$) buffers gastric acid ($HCl$), creating a neutral pH microenvironment.
- This allows the bacterium to burrow into the protective mucus layer.

H. pylori pathogenesis and immune response

⭐ CagA (Cytotoxin-associated gene A): An injected oncoprotein delivered by a type IV secretion system. It disrupts the cytoskeleton, increases cell proliferation, and is strongly associated with gastric adenocarcinoma.

Clinical Presentation - Belly's Burning Burden

Gastritis & Peptic Ulcers: Chronic, gnawing epigastric pain.
- Duodenal Ulcer (>90% assoc.): Pain improves with meals. More common.
- Gastric Ulcer (70% assoc.): Pain worsens with meals.
Increased Cancer Risk:
- MALT Lymphoma (can regress with H. pylori treatment).
- Gastric Adenocarcinoma.

⭐ The majority of duodenal ulcers are caused by H. pylori, whereas the association is strong but less frequent for gastric ulcers. This is a classic exam distinction.

Diagnosis - Finding the Fiend

Non-Invasive Tests (Initial Dx & Eradication Check)
- Urea Breath Test: High sensitivity & specificity. Detects active infection.
- Stool Antigen Assay: Good for initial diagnosis & post-treatment confirmation.
- Serology (IgG): Shows exposure, not active infection; less useful.
Invasive Tests (Endoscopy with Biopsy - Gold Standard)
- Rapid Urease Test (RUT): Quick, presumptive ID on biopsy sample.
- Histology: Warthin-Starry silver stain reveals spiral-shaped organisms.
- Culture: For antibiotic susceptibility testing, especially in treatment failure.

⭐ The Urea Breath Test relies on H. pylori’s urease splitting labeled urea into ammonia and labeled $CO_2$, which is detected in exhaled breath.

H. pylori in gastric biopsy (Warthin-Starry stain)

Treatment - Eviction Notice Protocol

Primary Goal: Eradicate H. pylori to prevent recurrence of peptic ulcers and reduce gastric cancer risk.
Standard First-Line Therapy (Triple):
- Proton Pump Inhibitor (PPI)
- Clarithromycin
- Amoxicillin (or Metronidazole if penicillin allergic)
**Quadruple Therapy (First-line in high resistance areas >15% or salvage):
- PPI
- Bismuth subsalicylate
- Metronidazole
- Tetracycline

⭐ For treatment failure, salvage therapy should avoid antibiotics used in the initial regimen. If triple therapy fails, switch to quadruple therapy or a levofloxacin-based regimen.

📌 Mnemonic (Quad Therapy): Please Make Tummy Better (PPI, Metronidazole, Tetracycline, Bismuth).

H. pylori is a Gram-negative, spiral-shaped bacterium strongly linked to peptic ulcer disease (especially duodenal ulcers), gastric adenocarcinoma, and MALT lymphoma.

Its key virulence factor is urease, which hydrolyzes urea into ammonia, neutralizing gastric acid and allowing survival in the stomach.

The urea breath test is a common non-invasive diagnostic method.

Standard treatment is triple therapy: a proton pump inhibitor (PPI) plus two antibiotics, typically clarithromycin and amoxicillin.

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