Yersinia pseudotuberculosis 🦠 is a Gram-negative bacterium from the family Enterobacteriaceae, closely related to
Yersinia pestis (the cause of plague ⚰️).
It is primarily a zoonotic pathogen 🐀🐓🐑, infecting animals but also humans via contaminated food or water.
Named in 1883 due to its resemblance to tuberculosis in animals, it shows a classic "safety pin" 🔍 appearance on Giemsa staining.
Characteristics 🔬
- Gram-negative rods (1–3 μm).
- Facultative anaerobe: grows with or without oxygen.
- Glucose fermenting (no gas).
- Oxidase negative, catalase positive ⚡.
- Reduces nitrates ➝ nitrites.
- Uses adhesins, invasins, and a type III secretion system to enter host cells and evade immunity.
- Psychrotrophic: survives at low temps ❄️ → thrives in refrigerated food.
Source 🥦🥛
- Reservoirs: wild/domestic animals (rodents, birds, cattle, sheep, goats).
- Transmission: contaminated food (vegetables 🥦, unpasteurised milk 🥛, water 💧) or direct contact with animals.
- Outbreaks often food-borne or linked to farm/animal exposure.
- Less common in humans than Y. enterocolitica, but can cause systemic illness.
Pathogenicity ⚠️
- Mesenteric adenitis: mimics appendicitis in children → “pseudoappendicitis” 👨⚕️.
- Septicaemia 🩸: risk in immunocompromised patients.
- Reactive arthritis 🤕: post-infectious complication.
- Gastroenteritis: abdominal pain, fever, diarrhoea (self-limiting).
- Systemic infection: rare - can affect liver, spleen, heart valves.
- Pseudotuberculosis: forms caseating granulomas resembling TB 🫁.
Investigations 🧪
- Stool culture on CIN agar 🍵: selective for Yersinia (red colonies with "bullseye" centre).
- Blood cultures: in suspected septicaemia.
- Serology: useful for systemic/reactive disease.
- PCR 🧬: rapid detection in stool/blood/tissue.
- Histopathology: mesenteric node biopsy → granulomatous inflammation.
Treatment 💊
- Mild gastroenteritis: usually self-limiting → supportive care (hydration, rest 🛌).
- Severe/systemic disease: aminoglycosides, fluoroquinolones, or tetracyclines.
- Surgery 🩺: for complications (abscess drainage, pseudoappendicitis).
Prevention ✅
- Good food hygiene 🍽️ and handwashing 🧼.
- Cook food properly, pasteurise milk 🥛.
- Rodent control and farm sanitation 🐀🚫.
Key Clinical Pearl ✨
In children with RIF abdominal pain mimicking appendicitis, consider Y. pseudotuberculosis - especially if there’s a history of animal contact or contaminated food exposure.
