Yersinia, Pasteurella and Francisella

Question 1

[7-minute video]: Yersinia pestis and Yersinia Enterocolitica

Answer 1

🐀

Question 2

Yersinia pestis general characteristics

Answer 2

✔ gram-negative coccobacilli
✔ non-motile
✔ exhibits bipolar staining with Giemsa, Wright’s or Wayson staining (safety pin appearance) [Image]
✔ facultative anaerobe
✔ facultative intracellular pathogen
✔ non-spore-forming

Question 3

Discuss reservoirs, vectors and transmission of Yersinia pestis.

Answer 3

🐀 The primary reservoirs of Y. pestis are various rodent species including wild rodents like rats, prairie dogs, and squirrels.
🐀 Fleas act as the primary vectors, transmitting the bacteria from infected rodents to other animals, including humans.
🐀 Humans can also become infected by handling infected animal tissues or fluids, such as when skinning infected animals.
🐀 Pneumonic plague, the lung-based form, can spread through respiratory droplets from person to person, making it highly contagious.

Question 4

main species of fleas involved in transmission of Y. pestis

Answer 4

Xenopsylla cheopis, Xenopsylla brasiliensis

Question 5

Y. pestis virulence factors

Answer 5

(1) capsule
(2) LPS; endotoxin activity
(3) ability to absorb iron
(4) Type III secretion system; enables the bacteria to inject proteins directly into host cells

Question 6

3 types of infections caused by Y. pestis

Answer 6

(1) Bubonic plague
(2) Septicaemic plague
(3) Pneumonic plague

Question 7

general characteristics of Pasteurella multocida

Answer 7

◾ gram-negative rods or coccobacilli
◾ facultative anaerobes
◾ non-motile
◾ non-sporing
◾ capsulated
◾ bipolar staining
◾ fermenters
◾ oxidase positive

Question 8

Pasteurella multocida virulence factors

Answer 8

◾ iron acquisition mechanisms
◾ membrane LPS
◾ capsule
◾ adhesins e.g. filamentous hemagglutinin
◾ extracellular matrix-degrading enzymes e.g. hyaluronidase, neuraminidase, proteases
◾ dermonecrotic toxin (in highly virulent strains)
◾ Pasteurella multocida toxin

Question 9

briefly discuss epidemiology and transmission of P. multocida

Answer 9

✔ Comprises normal microbiota of the oral, nasopharyngeal and upper respiratory tracts of many wild and domestic animals.
✔ Transmitted via bite or scratch wounds from pets, predominantly cats and dogs, respiratory droplets