Today’s question comes from a commonly tested GI/micro concept. This one shows up repeatedly, so be sure to fully understand the condition, how to diagnose it, and the associated risk factors—including the MC risk factor. Good luck!
A 47-year-old male presents to the clinic with a 3-week history of epigastric pain, nausea, and occasional vomiting. He has no significant past medical history. On examination, his temperature is 98.6°F (37°C), heart rate is 85/minute, respiratory rate is 16/minute, and blood pressure is 120/80 mmHg. Physical examination reveals mild epigastric tenderness without rebound or guarding. The stool antigen test is positive. Endoscopy reveals chronic active gastritis. An organism with which of the following characteristics is most likely responsible for these findings?
A) Oblong, gram-negative bacilli
B) Spiral-shaped, gram-positive cocci
C) Spiral-shaped, gram-negative bacilli
D) Rod-shaped, gram-positive cocci
E) Filamentous, gram-negative bacilli
F) Coccobacillary, gram-positive bacilli
Detailed Breakdown of Answers + Correct Answer Below ⏬
ANSWER + QUESTION BREAKDOWN
The mental model for this week’s question comes from our detailed test-taking skills masterclass. Here’s how to think about this question for maximum efficiency and accuracy:
Step 1. Figure out what they’re asking us to answer (organism characteristics—i.e., we will probably have to make a diagnosis, recognize the responsible organism, and recognize its characteristics, features, or structure).
Step 2. Read the vignette and make a diagnosis.
Step 3. Ask yourself which organism is responsible (most likely) for the diagnosis.
Step 4. Look at the answer choices and select the one that matches your answer or is closest to it.
** Always remember to come up with an answer in your head before looking at the answer choices… This will help you avoid second-guessing yourself and/or minimize the risk of falling for a distractor **
GENERAL ANALYSIS
This question involves a 47-year-old male with symptoms of epigastric pain, nausea, and vomiting, along with a positive stool antigen test and biopsy findings of chronic active gastritis. The question asks for the structural description of the organism responsible for these symptoms. Given the context, the organism is likely Helicobacter pylori, a common cause of chronic gastritis.
ANSWER CHOICES:
ANSWER CHOICE A: Oblong, gram-negative bacilli
Oblong bacilli refer to rod-shaped bacteria, which are typically straight.
ANSWER CHOICE B: Spiral-shaped, gram-positive cocci
Spiral-shaped cocci are spherical bacteria with a spiral form, which is atypical.
ANSWER CHOICE C: Spiral-shaped, gram-negative bacilli
This describes bacteria that are spiral in shape and have a gram-negative cell wall structure.
ANSWER CHOICE D: Rod-shaped, gram-positive cocci
This is a contradictory description, as cocci are spherical, not rod-shaped.
ANSWER CHOICE E: Filamentous, gram-negative bacilli
Filamentous bacteria are long and thread-like; this is not descriptive of H. pylori.
ANSWER CHOICE F: Coccobacillary, gram-positive bacilli
Coccobacilli are short and plump, intermediate between cocci and bacilli.
FINAL VERDICT…
Helicobacter pylori is a gram-negative bacterium with a distinctive spiral shape, which allows it to penetrate the gastric mucosa and establish infection in the stomach lining. This bacterium is a well-known cause of chronic gastritis and peptic ulcer disease (other common risk factors include stress, NSAIDs, and chronic ETOH use). The spiral shape and flagella of H. pylori facilitate its movement through the mucus layer of the stomach, allowing it to colonize and persist in the acidic environment. The gram-negative cell wall structure of H. pylori is characteristic of many pathogenic bacteria, contributing to its ability to evade the host immune response and cause chronic infection.
CORRECT ANSWER: C) Spiral-shaped, gram-negative bacilli