[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Enterobacterales](https://durgical.com/en/microbiology/groups/enterobacterales/) › Yersinia

[Microbiology](https://durgical.com/en/microbiology/) · [Enterobacterales](https://durgical.com/en/microbiology/groups/enterobacterales/)

# Yersinia

- Bacterium
- Gram-negative
- Droplet
- For completeness

A genus with Y. pestis, which causes plague through rodent flea bites, and Y. enterocolitica, which causes diarrhea from pork.

Updated 2026-11-01

Also called: Yersinia pestis, Yersinia enterocolitica, plague bacillus

## Key points

- Bipolar "safety pin" staining: Yersinia pestis.
- Rodent flea and a painful bubo: bubonic plague; pneumonic plague spreads between people and needs droplet precautions.
- Y. enterocolitica: pork, growth in the cold and pseudoappendicitis.
- Iron overload or deferoxamine: Yersinia sepsis.
- Plague: treated with aminoglycosides, fluoroquinolones or doxycycline.

## At a glance

**Gram**
Gram-negative

**Shape**
Coccobacillus; Y. pestis stains bipolar ("safety pin")

**Oxygen**
Facultative anaerobe

**Family**
Yersiniaceae

**Stain**
Giemsa or Wayson: dark staining at both ends

## Morphology

- Gram-negative coccobacillus; Y. pestis non-motile, Y. enterocolitica motile at room temperature
- Non-lactose fermenters
- Y. enterocolitica grows in the cold (survives in refrigerated food and stored blood)

## Transmission

- Plague: bites of infected rodent fleas, contact with animal tissues and, in the pneumonic form, respiratory droplets between people
- Y. enterocolitica: raw or undercooked pork, unpasteurized milk, untreated water
- Droplet (on top of standard) for pneumonic plague

**Reservoir:** Wild rodents and their fleas (Y. pestis); Pigs (Y. enterocolitica)

**Vector:** Rodent fleas (Y. pestis).

### Isolation precautions

What the care team adds to standard precautions.

**Droplet**
Surgical mask within about a metre; single room.

## Virulence factors

- F1 capsule and V and W antigens: resist phagocytosis
- Yop proteins injected through a type III secretion system: paralyze macrophages
- Rapid growth in lymph nodes (buboes) and blood
- Y. enterocolitica invades the terminal ileum and mesenteric nodes; iron overload (deferoxamine) raises the risk of sepsis

## Diseases it causes

- Bubonic, septicemic and pneumonic plague [Plague →](https://durgical.com/en/conditions/plague/)
- Y. enterocolitica gastroenteritis with mesenteric adenitis that mimics appendicitis [Acute (viral) gastroenteritis →](https://durgical.com/en/conditions/acute-gastroenteritis/)

## Clinical picture

- Bubonic plague: sudden fever and a very painful swollen node (bubo) near the bite
- Pneumonic plague: severe, contagious pneumonia, fatal without early treatment
- Y. enterocolitica: fever and right lower quadrant pain (pseudoappendicitis); later reactive arthritis or erythema nodosum

## Diagnosis

- Plague: culture or stain of bubo aspirate, blood or sputum; rapid F1 antigen test
- Y. enterocolitica: stool culture on CIN agar (alert the lab), stool PCR

## Treatment

Plague: immediate antibiotics with aminoglycosides (streptomycin or gentamicin), fluoroquinolones or doxycycline. Y. enterocolitica: most cases clear without antibiotics; severe cases get fluoroquinolones, trimethoprim-sulfamethoxazole or third-generation cephalosporins.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

- [Gentamicin](https://durgical.com/en/pharmacology/gentamicin/)
- [Streptomycin](https://durgical.com/en/pharmacology/streptomycin/)
- [Ciprofloxacin](https://durgical.com/en/pharmacology/ciprofloxacin/)
- [Doxycycline](https://durgical.com/en/pharmacology/doxycycline/)

## Prevention

- Rodent and flea control; not handling dead animals
- Antibiotic prophylaxis for contacts of pneumonic plague
- Cook pork through and use pasteurized milk
- Plague vaccine only for high-risk groups

## In Colombia

There are no known plague foci in Colombia; in South America foci persist in rural areas of Andean countries. Y. enterocolitica is sought in diarrhea with right lower quadrant pain.

## Memory aid

"Yersinia, the safety pin and the fridge": Y. pestis stains like a safety pin and Y. enterocolitica survives in the refrigerator.

## Test yourself

Think of the answer, then tap the question to see it.

## How is bubonic plague transmitted?

By the bite of infected rodent fleas or contact with infected animal tissue.

## Which form of plague spreads between people, and which precaution does it need?

Pneumonic plague; it needs droplet precautions on top of standard.

## Which gut infection mimics appendicitis and is linked to pork?

Yersinia enterocolitica infection (mesenteric adenitis and terminal ileitis).

## What does Y. pestis look like on Giemsa or Wayson stain?

Coccobacilli staining darker at both ends, like a safety pin.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/yersinia/)

## Related

- [Francisella tularensis](https://durgical.com/en/microbiology/francisella-tularensis/)
- [Brucella](https://durgical.com/en/microbiology/brucella/)

## Related conditions

- [Plague](https://durgical.com/en/conditions/plague/)
- [Acute (viral) gastroenteritis](https://durgical.com/en/conditions/acute-gastroenteritis/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

**Contact**
Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.

**Droplet**
Surgical mask within about a metre; single room.

**Airborne**
N95 respirator and a negative-pressure room.

[← Back to the group: Enterobacterales](https://durgical.com/en/microbiology/groups/enterobacterales/)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Plague](https://www.who.int/news-room/fact-sheets/detail/plague) (WHO, 2026); [About Plague](https://www.cdc.gov/plague/about/index.html) (CDC, 2026); [About Yersinia Infection](https://www.cdc.gov/yersinia/about/index.html) (CDC, 2024).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/yersinia/