Yersinia pseudotuberculosis ๐ฆ is a Gram-negative bacterium from the family Enterobacteriaceae, closely related to
Yersinia pestis (the cause of plague โฐ๏ธ).
It is primarily a zoonotic pathogen ๐๐๐, 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" ๐ appearance on Giemsa staining.
Characteristics ๐ฌ
- Gram-negative rods (1โ3 ฮผm).
- Facultative anaerobe: grows with or without oxygen.
- Glucose fermenting (no gas).
- Oxidase negative, catalase positive โก.
- Reduces nitrates โ nitrites.
- Uses adhesins, invasins, and a type III secretion system to enter host cells and evade immunity.
- Psychrotrophic: survives at low temps โ๏ธ โ thrives in refrigerated food.
Source ๐ฅฆ๐ฅ
- Reservoirs: wild/domestic animals (rodents, birds, cattle, sheep, goats).
- Transmission: contaminated food (vegetables ๐ฅฆ, unpasteurised milk ๐ฅ, water ๐ง) 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 โ ๏ธ
- Mesenteric adenitis: mimics appendicitis in children โ โpseudoappendicitisโ ๐จโโ๏ธ.
- Septicaemia ๐ฉธ: risk in immunocompromised patients.
- Reactive arthritis ๐ค: post-infectious complication.
- Gastroenteritis: abdominal pain, fever, diarrhoea (self-limiting).
- Systemic infection: rare โ can affect liver, spleen, heart valves.
- Pseudotuberculosis: forms caseating granulomas resembling TB ๐ซ.
Investigations ๐งช
- Stool culture on CIN agar ๐ต: selective for Yersinia (red colonies with "bullseye" centre).
- Blood cultures: in suspected septicaemia.
- Serology: useful for systemic/reactive disease.
- PCR ๐งฌ: rapid detection in stool/blood/tissue.
- Histopathology: mesenteric node biopsy โ granulomatous inflammation.
Treatment ๐
- Mild gastroenteritis: usually self-limiting โ supportive care (hydration, rest ๐).
- Severe/systemic disease: aminoglycosides, fluoroquinolones, or tetracyclines.
- Surgery ๐ฉบ: for complications (abscess drainage, pseudoappendicitis).
Prevention โ
- Good food hygiene ๐ฝ๏ธ and handwashing ๐งผ.
- Cook food properly, pasteurise milk ๐ฅ.
- Rodent control and farm sanitation ๐๐ซ.
Key Clinical Pearl โจ
In children with RIF abdominal pain mimicking appendicitis, consider Y. pseudotuberculosis โ especially if thereโs a history of animal contact or contaminated food exposure.
