Yersinia

Question 1

Is yersinia pestis common in the intestine?

Answer 1

No

- causes plague

Question 2

Y. pestis

Answer 2

Gram neg, non-motile, coccobacillus, non-hemolytic, non-lactose fermenting

• does not survive long in environment
• grows slowly at 28 C

Question 3

Endemic disease in animals

Answer 3

Voles and deer mice (usually do not have serous disease)

Question 4

Accidental animal hosts

Answer 4

• cattle, horses, swine, and sheep are not susceptible

- wild and domestic cats can acquire infection by ingesting infected rodents

Question 5

Disease in cats

Answer 5

Bubonic plague is most common

• lymphadenitis
• fatal
• need to isolate cases and report to CDC

Question 6

Human disease

Answer 6

Bubonic plague is most common

• pneumonic plague: most serious form of disease, the only form of plague that can spread from person to person
• septicemic plague: progression from either bubonic or pneumonic plague

Question 7

Transmission

Answer 7

• infected flea bites (sylvatic plague), which leads to bubonic plague
• infected cats thru scratches or bites

Question 8

How is Y. pestis shed?

Answer 8

From infected people/cats thru sputum or respiratory droplets
- directly spread from human to human

Question 9

Flea transmission

Answer 9

Spread through infected Oriental rat fleas, who feed on rats and rodents
- cat and dog fleas do not transmit Y. pestis efficiently

Question 10

Virulence factors

Answer 10

• LPS
• capsule (F1)
• type 3 secretion system
• iron acquisition

Question 11

Pathogenesis

Answer 11

Phagosome-lysosome fusion occurs, but Y. pestis is able to survive in mononuclear cells

• survival in macrophages is by effectors from type 3 secretion system (Yops) to inhibit phagocytosis and proinflammatory cytokine release
• Yops also trigger apoptosis of macrophage

Question 12

Y. pseudotuberculosis

Answer 12

Enteropathogen of wild and domestic animals

• genetically similar to Y. pestis
• can persist in the environment

Question 13

Y. pseudotuberculosis disease

Answer 13

Transmitted by fecal-oral route

• acute: blood, mucoid diarrhea, gasteroenteritis, death within 24-48 hrs
• chronic: caseous abcesses in intestinal wall, mesenteric lymph nodes, liver, spleen (similar in tuberculosis)

Question 14

Who are reservoirs of Y. pseudotuberculosis?

Answer 14

Gregarious wild birds

• blackbirds, grackles, starlings
• rats

Question 15

Who is the most commonly infected domestic animal?

Answer 15

Cats

- especially adult rural outdoor cats

Question 16

What is a difference between Y. pseudotuberculosis and Y. pestis?

Answer 16

Disease is usually limited to gastroenteritis

Question 17

Pathogenesis of Y. pseudotuberculosis

Answer 17

3 adhesins that adhere to luminal surface of M cells and basolateral surfaces of ileal enterocytes

• Ail, Inv, and Yad
• all 3 are outer membrane proteins
• passes thru M cells, afterwards pathogenesis is similar to Y. pestis
• facultative intracellular parasite of macrophages

Question 18

What causes diarrhea in Y. pseudotuberculosis?

Answer 18

Prostaglandin synthesis from recruited neutrophils

Question 19

Diagnosis

Answer 19

Culture from feces or lymph node aspirates

- benefited by cold enrichment at 4 C for several weeks

Question 20

Who are carriers for Y. enterocolitica?

Answer 20

Swine

- one of the major sources of human infection with serobiotype O:3/4 is thru handling of swine and consumption of pork

Question 21

Y. enterocolitica disease

Answer 21

Gastroenteritis, bloody diarrhea, ileitis, mesenteric adenitis in people and animals, pseudoappendicitis in people
- similar clinical signs to Y. pseudotuberculosis

Question 22

Pathogenesis of Y. enterocolitica

Answer 22

Invasion through M cells

- initially is an intracellular pathogen in macrophages, then it becomes extracellular

Question 23

Y. ruckeri

Answer 23

Enteric red-mouth disease of salmon and trout

• transmitted through direct contact or through fomites
• hemorrhagic septicemia: hemorrhages on body surface and around mouth

Question 24

Who is most susceptible to Y. ruckeri?

Answer 24

Rainbow trout

- bacterin is effective in controlling