Yersinia Enterocolitica

  Yersinia enterocolitica is a gram-negative bacillus that is known for causing gastroenteritis. [1]

Staining and microbiologic features:    

•  Test positive for urease and negative for catalase [2]
• Motile and unable to ferment lactose [1,2] 
• Safety pin-like/ bipolar appearance on staining [3] 
• Culture on MacConkey agar yields non-lactose fermenting colonies [4] 
• It shows optimum growth at low temperatures, i.e., at 25°C [2]
• Its motility can be absent at high temperatures, i.e., at 37°C [2]
• Cefsulodin-irgasan-novobiocin (CIN) agar is a yersinia selective agar. Cultivation on CIN agar will yield colonies with a bull’s eye appearance. [2]
• Different serotypes of Yersinia enterocolitica have distinct geographic distributions. Serotypes O3 and O9 are prevalent in Africa, Japan, Canada, and Europe. Serotype O8 is notable in the USA. [5]
• As Yersinia enterocolitica can survive at low temperatures, cold enrichment technique can isolate the organism from stool samples. This technique involves incubating the stool sample at a temperature of 4°C and a pH of 7.6 for up to a month. [2]

Virulence:

• The enterotoxin produced by Yersinia enterocolitica enhances guanylate cyclase activity, leading to elevated cGMP levels in intestinal cells and promoting diarrhea. The heat-stable toxin produced by E. Coli also elevates cGMP levels. [6,7] 
• Produces V and W antigens [8]
•  It can directly deliver its virulence factors into host cells using its type III secretion systems.[9]
•  It can also evade the phagocytic action of macrophages by dephosphorylating macrophage proteins, destroying macrophage cytoskeleton (especially actin), or promoting its programmed cell death. [9]
• Virulence factors of Yersinia enterocolitica are temperature-sensitive and are therefore expressed at 37°C. [8]

Transmission:

• Animals such as pigs/dogs are its major reservoir (zoonotic). [1,8,10]
• Consuming contaminated animal products (e.g., unpasteurized milk) [8]
• Consuming water/food contaminated with Yersinia enterocolitica (fecal-oral transmission) [1,8]

Diseases [2,4,5]:    

Yersinia enterocolitica can cause gastroenteritis, mesenteric adenitis or pseudoappendicits.

The disease mainly involves the terminal ileum and mesenteric lymph nodes. Following the consumption of contaminated food, Yersinia enterocolitica undergoes multiplication in intestinal cells, and subsequently, systemic invasion occurs. Affected patients may present with fever, right lower quadrant pain, and diarrhea. In children, the clinical presentation may mimic appendicitis, leading to the term ‘pseudoappendicitis.’

Diagnostic testing:  

•  Culture [2]
• A colonoscopy will show ulceration and inflammation of intestinal mucosa, particularly in the terminal ileum [6]. 
• Serological testing can detect elevated antibody levels against Yersinia enterocolitica. However, these antibodies can also cross-react with some other microorganisms [2].

References:

1. CMMRS edition 6, 2016-17 (page no: 79) 
2. Jawetz, Melnick, & Adelberg’s Medical Microbiology Twenty-Seventh Edition (page no: 277)
3. Sketchy Micro
4. Review of Medical Microbiology and Immunology, Seventeenth Edition 17th Edition by Warren Levinson, Peter Chin-Hong, Elizabeth A. Joyce, Jesse Nussbaum, and Brian Schwartz (page no: 215)
5. Medical Microbiology by Patrick R. Murray Ph.D., Ken Rosenthal Ph.D., Michael A. Pfaller MD, 8th edition (page no: 262)
6. CMMRS edition 6, 2016-17 (page no: 85)  
7. Platt-Samoraj A. Toxigenic Properties of Yersinia enterocolitica Biotype 1A. Toxins (Basel). 2022 Feb 5;14(2):118. doi: 10.3390/toxins14020118. PMID: 35202145; PMCID: PMC8877543.
8. CMMRS edition 6, 2016-17 (page no: 84) 
9. Medical Microbiology by Patrick R. Murray Ph.D., Ken Rosenthal Ph.D., Michael A. Pfaller MD, 8th edition (page no: 261)
10. Jawetz, Melnick, & Adelberg’s Medical Microbiology Twenty-Seventh Edition (page no: 275)