Makindo Medical Notes

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.