Makindo Medical Notes

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.