23 - Pathogenic Yersinia Species

Question 1

Yersinia genus

Answer 1

• Enterobacteriaceae family
• Gram negative, rod shaped bacillus
• Consists of 14 species

Question 2

Three well recognized pathogenic species in humans

Answer 2

• Yersinia enterocolitica
• Yersinia pseudotuberculosis
• Yersinia pestis

Question 3

Yersinia enterocolitica

Answer 3

• Enteric, causes Yersiniosis
• self-limiting gastroenteritis to terminal ileitis, mesenteric
  lymphadenitis, and septicemia in immunocompromised
  hosts
• Transmitted fecal orally via contaminated milk or pork, person to person transmission is rare
• Pigs are main reservoir

Question 4

Six biogroups of Yersinia enterocolitica

Answer 4

1A, 1B, 2, 3, 4 and 5

Question 5

Yersinia pseudotuberculosis

Answer 5

• Acute gastroenteritis, mesenteric lymphadenitis and diarrhoea, also mimicks acute or subacute appendicitis
• Found in rodents, rabbits, deer, birds
• Survives in water and environment
• Growth at 4ºC
• 21 different serological groups

Question 6

Yersinia pestis

Answer 6

• Evolved from Y. pseudotuberculosis
• Causes Plague, a severe, acute,
  and rapidly progressing febrile illness with significant mortality rates
• Sylvatic life cycle

Question 7

Three disease manifestations of Yersinia pestis

Answer 7

• Bubonic
• Septicaemic
• Pneumonic

Question 8

Transmission of plague

Answer 8

• Bite of infected fleas
• Inhaling infected droplets expelled by coughing
• Direct contact with contaminated tissue or body fluid

Question 9

Symptoms of Bubonic plague

Answer 9

• Headache, nausea, aching joints, and a general feeling of
  malaise
• Buboes (painful inflammation at lymph nodes in neck)
• Hemorrhaging under the skin,
  causing black splotches
• 50% Death if untreated

Question 10

Pneumonic plague

Answer 10

• Bacteria enter the lung
• Inhalation of contaminated droplets
• Symptoms include coughing, expulsion of slimy sputum with traces of blood, free flowing red sputum at later stages
• 95% death if untreated

Question 11

Septicemic plague

Answer 11

• When bacteria enter the bloodstream
• Symptoms include high fever, rash, gangrene, leading to
  respiratory failure
• Fatality is 100%
• Can cause disseminated intravascular coagulation, small blood clots throughout body that can result in ischemic necrosis

Question 12

Virulence determinants of Yersinia

Answer 12

• Plasminogen activator
• Murine toxin
• F1 capsular antigen
• T3SS

Question 13

Plasminogen activator (Pla protease)

Answer 13

• Transmembrane protease
• Encoded on plasmid pPCP1
• Has protease activity that interacts and cleaves host proteins targets
• Targets important in response to infection (e.g. coagulation and fibrin clot)
• Allows bacteria to disseminate from bite site and subversion of immune response

Question 14

Murine toxin

Answer 14

• Phospholipase D (PLD) activity
• Encoded by plasmid pMT1
• Required for survival in midgut of rat flea
• Intracellular PLD activity protects Y.pestis from a cytotoxic digestion product of blood plasma in the flea gut.
• Enables colonisation of the flea midgut
• Acquisition of PLD precipitated the transition of Y. pestis
  to obligate arthropod-borne transmission

Question 15

F1 capsular antigen

Answer 15

• Encoded by plasmid pMT1
• Forms a surface located polypeptide capsule at 37°C growth
• Antiphagocytic activity
• Good vaccine candidate
• Important but not essential for virulence

Question 16

T3SS

Answer 16

• Present in all three pathogenic Yersinia species
• Encoded on the pCD1 plasmid
• Expression activated by temperature change to 37ºC and presence of calcium
• Inject multiple toxic yersinia effector proteins (Yops) directly into host cells

Question 17

T3SS needle and translocon

Answer 17

• Injectisome
• Needle fixed into the bacterial
  inner and outer membrane and
  protrudes from the surface to
  penetrate host membrane
• Translocon forms a channel
  through host membrane
• Yop effectors transferred from
  the cytoplasm into the host cell

Question 18

LcrV

Answer 18

• V antigen essential for virulence
• Lack of LcrV leads to secretion of effectors into the extracellular environment
• Confers resistance to phagocytosis

Question 19

Direct delivery of Yops

Answer 19

• Mutants deficient in LcrV not cytotoxic
• Secreted proteins are not cytotoxic when added to tissue culture media
• But micro-injection of proteins
  leads to cytotoxicity
• Implied bacteria injected the host cell with Yops

Question 20

YopE

Answer 20

Disrupts Cytoskeleton

Question 21

YopH

Answer 21

Disrupts focal adhesions

Question 22

YopM

Answer 22

Regulation of host cell necrosis

Question 23

YopT

Answer 23

Disrupts actin filaments

Question 24

Invasin

Answer 24

• Chromosomally encoded adhesin
• Mediates attachment to and entry into host cells
• Inactive in Y. pestis
• Promotes phagocytosis and internalisation into epithelial cells

Question 25

YadA

Answer 25

- Non-fimbrial adhesin - Required for Y. enterocolitica pathogenicity