Yersenia Pestis Flashcards
Why Yersinia pestis is named as such?
According to its discoverer Alexandra Yersin
Why it is considered a part of the Enterobacteriaceae?
Since it is oxidase negative
Are they aerobic, anaerobic or facultative anaerobes?
facultative anaerobes
Are they spore forming? Are they motile?
Nonspore forming
Nonmotile
How it is transmitted?
- 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
Which disease does it cause when it is transmitted through a vector?
Bubonic plague
Which disease does it cause when it is transmitted through a vector?
Pneumonic plague
What are the virulence factors?
LPS Capsule Coagulase V-W Ag V exotoxin Pesticin toxin Proteases
What is the most virulence factor? To what it will lead?
LPS, it leads to septic shock
What do we call the capsule? What is its composition? What is its function and at which temperature it is expressed?
It is called fraction I, it is composed of proteins encoded by certain plasmids.
It is antiphagocytic and is expressed only at 37°C
When coagulase is produced?
At 28°C only, which is the temperature of the fleas not humans
What is the function of the V-W Ag?
It inhibits intracellular phagocytic killing that’s why they survive in phagocytic cells
What is the function of the V exotoxin?
It induces immunosuppression in infected hosts by decreasing the production of TNF and INF alpha
What is the pesticin toxin?
It’s a type of bacteriocins that kills specific bacteria of the same niche
What does proteases?
They bind plasminogen and breakdown many complement components
What happens if infection is left untreated?
This will kill within few days
What are the clinical presentations?
Bubonic plague
Pneumonic plague
In which species bubonic plague is endemic?
In rodents
What is the incubation period?
2 to 7 days
How bacteria are transmitted from fleas to humans?
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.
What is the most common outcome?
Bubonic plague with formation of bubo which a lymphadenopathy
What’s the primary place bacteria go to after surviving phagocytosis?
Lymphatic channels in the lymph nodes typically in the axilla and the groin region which swell
What happens after that?
Bacteria can cause a bacteremia with septicemia which has a high fatality rate
What’s the first systemic sign when it spreads?
High fever that’s above 38°C, accompanied with many G.I. disturbances like nausea, vomiting, hemorrhagic diarrhea.
What happens if the CNS is affected?
The person can develop delirium
What happens if lungs are involved in this case?
Where bacteria are found and what’s the outcome?
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
What happens if there is no treatment?
Death occurs within 2 to 6 days
What’s the incubation period in the case of pneumonic plague?
1 to 4 days
What leads to primary pneumonic plague?
Transmission of secondary pneumonic plague from person to person
Where bacteria are found?
In the alveoli
What’s the fatality rate? When death can occur? What’s the cause of death?
It is 100% fatal
Death is within 48 hours, because of necrosis, hemorrhage and quick progression
What’s the difference between a primary and secondary septicemic plague?
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
What are the preventions?
Hygiene and reduction of crowdedness
Which specimen could be taken for diagnosis ?
Sputum, blood, stool if there is diarrhea and sometimes from the CSF
Which stain other than the Gram stain is used? How bacteria will appear?
Wayson stain
We see a bipolar appearance of the bacteria similar to a safety pin
On which medium they grow?
On the MacConkey plate
Do they give permanent immunity?
All individuals who recover develop an immunity
To which antibiotics bacteria are sensitive?
Streptomycin
In some cases we give a combination of tetracycline and streptomycin
What’s the vaccine?
It’s a killed vaccine from the whole bacteria, it’s not for regular use, only when traveling through an endemic area
How Yersinia tuberculosis is transmitted?
By ingestion of contaminated meat
What’s the clinical presentation?
Food poisoning with diarrhea
What’s the treatment?
There is no treatment, it is self limited
