Campylobacter jejuni: Morphology and Identification, Antigenic Structure and Toxins, Pathogenesis and Pathology, Clinical Findings, Diagnostic Laboratory Tests, Epidemiology and Control.

Question 1

Campylobacter jejuni: morphology and identification

Answer 1

Campylobacter jejuni is a Gram-negative, curved or spiral-shaped bacillus, often described as ‘comma-shaped’ or ‘gull-winged.’ It is motile with a single polar flagellum and is oxidase-positive. It grows best in microaerophilic conditions (5% O₂, 10% CO₂, 85% N₂) at 42°C, which is higher than body temperature, aiding its selective isolation. It does not ferment carbohydrates and grows poorly on standard media, so selective media like Campy-BAP are used.

Question 2

Campylobacter jejuni: antigenic structure and toxins

Answer 2

C. jejuni possesses lipooligosaccharide (LOS) in its outer membrane, which is structurally similar to human gangliosides and plays a role in autoimmune reactions. Its flagellar antigens and capsule contribute to virulence. It produces a cytolethal distending toxin (CDT) that arrests the cell cycle in G2 phase, causing cell distension and death. Endotoxin (LPS-like) also contributes to inflammation.

Question 3

Campylobacter jejuni: pathogenesis and pathology

Answer 3

Infection typically results from ingestion of contaminated food (especially undercooked poultry), water, or unpasteurized milk. After ingestion, C. jejuni colonizes the intestinal mucosa, invades epithelial cells, and induces inflammation. CDT and LOS contribute to mucosal damage. The infection leads to ulceration, edema, and infiltration of neutrophils in the lamina propria, primarily in the jejunum, ileum, and colon.

Question 4

Campylobacter jejuni: clinical findings

Answer 4

The most common presentation is acute enteritis with fever, abdominal cramps, and diarrhea that may be bloody. Nausea and vomiting are also possible. The illness is usually self-limiting and lasts about a week. Rare but important complications include Guillain-Barré syndrome (autoimmune demyelinating neuropathy), reactive arthritis, and post-infectious irritable bowel syndrome (IBS).

Question 5

Campylobacter jejuni: diagnostic laboratory tests

Answer 5

Diagnosis is made by stool culture on selective media like Campy-BAP or Skirrow’s medium under microaerophilic conditions at 42°C. Colonies appear grayish and moist. Gram stain from stool may show curved rods. Biochemical tests confirm identity (oxidase-positive, hippurate hydrolysis positive for C. jejuni). PCR and EIA tests are also available for rapid detection.

Question 6

Campylobacter jejuni: epidemiology

Answer 6

Campylobacter is one of the most common causes of bacterial gastroenteritis worldwide. It has a low infectious dose and is frequently associated with consumption of contaminated poultry, unpasteurized milk, and untreated water. It is zoonotic and often harbored in the intestines of poultry and livestock. Human-to-human transmission is rare but can occur.

Question 7

Campylobacter jejuni: control

Answer 7

Prevention focuses on proper food handling—thorough cooking of poultry, avoiding cross-contamination in kitchens, pasteurizing milk, and ensuring safe drinking water. No vaccine exists. Personal hygiene, especially handwashing after handling raw meat or contact with animals, is critical to reduce transmission.