Yersinia enterocolitica 🦠 is a Gram-negative foodborne pathogen from the Enterobacteriaceae family.
It is notorious for surviving and growing in refrigerated food ❄️🥩, particularly pork and unpasteurised milk 🥛.
Under the microscope, with Giemsa stain, it shows the classic “safety pin” bipolar appearance 🔍.
About 📖
- Causes gastrointestinal infection and occasionally systemic illness in humans.
- Zoonotic pathogen found in pigs, rodents, rabbits, and contaminated environments.
- Important cause of gastroenteritis in Europe and temperate climates 🌍.
Characteristics 🔬
- Gram-negative rods: Small, rod-shaped bacilli.
- Facultative anaerobe: Can grow with or without oxygen.
- Glucose fermenting: Produces acid but no gas.
- Oxidase negative, catalase positive: Helps differentiate from other enteric pathogens.
- Nitrate reduction: Reduces nitrates to nitrites.
- Non-lactose fermenter: Appears as pale colonies on MacConkey agar 🧫, unlike E. coli.
- Can multiply at refrigeration temperatures ❄️, increasing food safety risks.
Clinical Features 🤒
- Zoonotic transmission: Acquired from undercooked pork 🥩, raw milk 🥛, contaminated water 💧, or direct animal contact 🐖.
- Gastroenteritis: Watery or sometimes bloody diarrhoea, abdominal pain, and fever. Incubation: 3–7 days.
- Mesenteric adenitis: Mimics appendicitis, especially in children → abdominal pain + tender right iliac fossa.
- Enteric fever-like illness: Severe invasive infection with prolonged fever and colitis.
- Post-infectious complications: Reactive arthritis in HLA-B27 adults, sometimes erythema nodosum.
Investigations 🧪
- Stool culture on CIN agar: Selective medium that shows characteristic “bull’s-eye” colonies 🎯.
- Blood cultures: In systemic disease or sepsis.
- Serology: Detects antibodies in chronic/systemic infections.
Management 💊
- Supportive: Rehydration 💧, electrolyte replacement, and symptomatic relief.
- Antibiotics: Reserved for severe/systemic cases (fluoroquinolones, doxycycline, or trimethoprim-sulfamethoxazole).
⚠️ Not routinely indicated for mild gastroenteritis.
Prevention 🛡️
- Cook pork thoroughly to safe internal temperatures 🥩🔥.
- Avoid unpasteurised milk and untreated water 🥛🚫.
- Strict food hygiene and prevention of cross-contamination in kitchens 🍴.
- Proper refrigeration of food at <4°C ❄️ slows but does not eliminate growth.
Key Clinical Pearl ✨
In a child with RLQ abdominal pain and fever but normal appendix on surgery, think of Yersinia enterocolitica mesenteric adenitis.
