Question:medium
Several residents in a village develop watery followed by bloody diarrhea after consuming unpasteurized milk. Stool microscopy reveals Gram-negative curved bacilli with polymorphonuclear leukocytes. Identify the most likely pathogen.
Several residents in a village develop watery followed by bloody diarrhea after consuming unpasteurized milk. Stool microscopy reveals Gram-negative curved bacilli with polymorphonuclear leukocytes. Identify the most likely pathogen.
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Unpasteurized milk + bloody diarrhea + curved Gram-negative bacilli = Campylobacter jejuni.
Updated On: May 14, 2026
- Clostridium perfringens
- Staphylococcus aureus
- Vibrio parahaemolyticus
- Campylobacter jejuni
Show Solution
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Question:
The clinical presentation is inflammatory diarrhea (watery then bloody) following unpasteurized milk consumption. The lab finding of "Gram-negative curved bacilli" and PMNs (indicating inflammation) is the definitive clue.
Step 2: Detailed Explanation:
Campylobacter jejuni: A major cause of bacterial gastroenteritis worldwide. It is commonly transmitted through contaminated poultry or unpasteurized milk.
Morphology: They are characteristically described as "seagull-wing" shaped, Gram-negative curved or spiral rods. They are motile (darting motility).
Clinical Features: Diarrhea is initially watery but often becomes bloody due to the invasive nature of the bacteria causing enteritis. The presence of leukocytes (PMNs) in stool microscopy confirms an invasive, inflammatory process.
Culture: They are microaerophilic and grow best at 42$^\circ$C on selective media (like Skirrow’s or Butzler’s medium).
Why not others? Vibrio parahaemolyticus (Option C) also shows curved bacilli but is almost exclusively associated with contaminated seafood/shellfish, not milk. S. aureus and C. perfringens (Options A and B) cause toxin-mediated food poisoning, usually without blood or curved rods on microscopy.
Step 3: Final Answer:
Campylobacter jejuni is the most likely pathogen given the association with milk and the seagull-wing morphology.
The clinical presentation is inflammatory diarrhea (watery then bloody) following unpasteurized milk consumption. The lab finding of "Gram-negative curved bacilli" and PMNs (indicating inflammation) is the definitive clue.
Step 2: Detailed Explanation:
Campylobacter jejuni: A major cause of bacterial gastroenteritis worldwide. It is commonly transmitted through contaminated poultry or unpasteurized milk.
Morphology: They are characteristically described as "seagull-wing" shaped, Gram-negative curved or spiral rods. They are motile (darting motility).
Clinical Features: Diarrhea is initially watery but often becomes bloody due to the invasive nature of the bacteria causing enteritis. The presence of leukocytes (PMNs) in stool microscopy confirms an invasive, inflammatory process.
Culture: They are microaerophilic and grow best at 42$^\circ$C on selective media (like Skirrow’s or Butzler’s medium).
Why not others? Vibrio parahaemolyticus (Option C) also shows curved bacilli but is almost exclusively associated with contaminated seafood/shellfish, not milk. S. aureus and C. perfringens (Options A and B) cause toxin-mediated food poisoning, usually without blood or curved rods on microscopy.
Step 3: Final Answer:
Campylobacter jejuni is the most likely pathogen given the association with milk and the seagull-wing morphology.
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