Yersenia Pestis

Question 1

Why Yersinia pestis is named as such?

Answer 1

According to its discoverer Alexandra Yersin

Question 2

Why it is considered a part of the Enterobacteriaceae?

Answer 2

Since it is oxidase negative

Question 3

Are they aerobic, anaerobic or facultative anaerobes?

Answer 3

facultative anaerobes

Question 4

Are they spore forming? Are they motile?

Answer 4

Nonspore forming

Nonmotile

Question 5

How it is transmitted?

Answer 5

• Vector borne, which is the most best mode of transmission, fleas or parasites transmit it from infected rodents or other animals to humans through biting
• From animals by direct contact e.g. by biting of infected rat, ingestion of contaminated food, or inhalation of the exhaled breath, or blood splashes during slaughtering
• Person to person spread by droplets

Question 6

Which disease does it cause when it is transmitted through a vector?

Answer 6

Bubonic plague

Question 7

Which disease does it cause when it is transmitted through a vector?

Answer 7

Pneumonic plague

Question 8

What are the virulence factors?

Answer 8

LPS
Capsule
Coagulase
V-W Ag
V exotoxin
Pesticin toxin
Proteases

Question 9

What is the most virulence factor? To what it will lead?

Answer 9

LPS, it leads to septic shock

Question 10

What do we call the capsule? What is its composition? What is its function and at which temperature it is expressed?

Answer 10

It is called fraction I, it is composed of proteins encoded by certain plasmids.
It is antiphagocytic and is expressed only at 37°C

Question 11

When coagulase is produced?

Answer 11

At 28°C only, which is the temperature of the fleas not humans

Question 12

What is the function of the V-W Ag?

Answer 12

It inhibits intracellular phagocytic killing that’s why they survive in phagocytic cells

Question 13

What is the function of the V exotoxin?

Answer 13

It induces immunosuppression in infected hosts by decreasing the production of TNF and INF alpha

Question 14

What is the pesticin toxin?

Answer 14

It’s a type of bacteriocins that kills specific bacteria of the same niche

Question 15

What does proteases?

Answer 15

They bind plasminogen and breakdown many complement components

Question 16

What happens if infection is left untreated?

Answer 16

This will kill within few days

Question 17

What are the clinical presentations?

Answer 17

Bubonic plague

Pneumonic plague

Question 18

In which species bubonic plague is endemic?

Answer 18

In rodents

Question 19

What is the incubation period?

Answer 19

2 to 7 days

Question 20

How bacteria are transmitted from fleas to humans?

Answer 20

At 28°C in the flea, bacteria produce coagulase that closes the proventriculus of the flea. The flea gets hungry, it goes to humans to suck their blood through a bite. The flea regurgitates the bacteria in the blood.

Question 21

What is the most common outcome?

Answer 21

Bubonic plague with formation of bubo which a lymphadenopathy

Question 22

What’s the primary place bacteria go to after surviving phagocytosis?

Answer 22

Lymphatic channels in the lymph nodes typically in the axilla and the groin region which swell

Question 23

What happens after that?

Answer 23

Bacteria can cause a bacteremia with septicemia which has a high fatality rate

Question 24

What’s the first systemic sign when it spreads?

Answer 24

High fever that’s above 38°C, accompanied with many G.I. disturbances like nausea, vomiting, hemorrhagic diarrhea.

Question 25

What happens if the CNS is affected?

Answer 25

The person can develop delirium

Question 26

What happens if lungs are involved in this case?

Where bacteria are found and what’s the outcome?

Answer 26

We have a secondary pneumonic plague because it follows a bubonic plague
Bacteria are in the interstitial spaces and there is hemorrhagic pneumonia and coughing of the bacteria

Question 27

What happens if there is no treatment?

Answer 27

Death occurs within 2 to 6 days

Question 28

What’s the incubation period in the case of pneumonic plague?

Answer 28

1 to 4 days

Question 29

What leads to primary pneumonic plague?

Answer 29

Transmission of secondary pneumonic plague from person to person

Question 30

Where bacteria are found?

Answer 30

In the alveoli

Question 31

What’s the fatality rate? When death can occur? What’s the cause of death?

Answer 31

It is 100% fatal

Death is within 48 hours, because of necrosis, hemorrhage and quick progression

Question 32

What’s the difference between a primary and secondary septicemic plague?

Answer 32

Primary septicemic plague is acquired from animal adapted strains not through factors, it is severe, and kills in a shorter time. In this case, bacteremia is direct, there is no passage through lymph

Question 33

What are the preventions?

Answer 33

Hygiene and reduction of crowdedness

Question 34

Which specimen could be taken for diagnosis ?

Answer 34

Sputum, blood, stool if there is diarrhea and sometimes from the CSF

Question 35

Which stain other than the Gram stain is used? How bacteria will appear?

Answer 35

Wayson stain

We see a bipolar appearance of the bacteria similar to a safety pin

Question 36

On which medium they grow?

Answer 36

On the MacConkey plate

Question 37

Do they give permanent immunity?

Answer 37

All individuals who recover develop an immunity

Question 38

To which antibiotics bacteria are sensitive?

Answer 38

Streptomycin

In some cases we give a combination of tetracycline and streptomycin

Question 39

What’s the vaccine?

Answer 39

It’s a killed vaccine from the whole bacteria, it’s not for regular use, only when traveling through an endemic area

Question 40

How Yersinia tuberculosis is transmitted?

Answer 40

By ingestion of contaminated meat

Question 41

What’s the clinical presentation?

Answer 41

Food poisoning with diarrhea

Question 42

What’s the treatment?

Answer 42

There is no treatment, it is self limited