(Section C: Bacteriology) Lecture 19: Flashcards
Describe:
Yersinia
* Gram stain
* Shape
* Strains
- Gram negative
- Rod shaped
- Bacteria
- 3 strains pathogenic to humans
What are the 3 strains of Yersinia that are pathogenic for humans?
- Y. enterocolitica
- Y. pseudotuberculosis
- Y. pestis
Y. enterocolitica
Causes “yersiniosis” - a rare cause of diarrhea and abdominal pain
Y. pseudotuberculosis
Primarily an animal pathogen that can cause tuberculosis-like symptoms in animals, enteritis in humans
Y. pestis
Cause of the plague
What are key characteristics of Yersinia pestis?
- Extraordinarily virulent pathogen
- May cause death in 2-4 days by sepsis and/or overwhelming pneumonia with respiratory failure
- NOT an efficient colonizer of humans
History of Yersinia pestis discovery and namesake
- Discovered by Alexandre Yersin (namesake) and Kitasato Shibasaburo in the late 1800s
- Pestis = Pestilence (contagious or infectious epidemic disease)
Plague:
- Incubation period
- Death period
- 3-7 days
- 2-4 days
Plague:
General signs and symptoms (early stage)
Sudden onset of:
1. Fever
2. Chills
3. Headaches
4. Muscle pain
5. Weakness
Plague:
Signs and symptoms (lymph nodes)
Painful swellings (buboes) of lymph nodes in:
* Armpits
* Legs
* Neck
* Groin
Plague:
Signs and symptoms (late stage)
- High fever
- Delirium
- Mental deterioration
- Large blackish pustules that burst
- Vomiting of blood
- Bleeding in the lungs
What were the 3 plague pandemics?
- “Plague of Justinian”
- “Black Death”
- Mid 19th Century
Plague of Justinian
* Date
* Cause
* Area
* Death
- Started in the 6th century (541-542 AD)
- Caused by Yersinia pestis
- Mediterranean, Italy and throughout Europe
- ~50% of population died, around 100 million people killed
What happened after the initial plague during the “Plague of Justinian”?
Continued in cycles for 200 years until 750 AD
* Disappears for ~800 years
Black Death
* Date
* Cause
* Area
* Death
- Late 1340s (spread to Europe)
- Caused by Yersinia pestis
- Originated in Asia, reached Europe in late 1340s
- ~100 million globally, ~25 million Europeans (1/3 of population)
What was society’s reaction to the Black Death during its time?
- No idea what was going on
- No (real) treatment
- Believed it was “God’s anger” or “Satan’s influence”
- Persecuted strangers, minorities, and witches
- European social order and such was destroyed
What was the Feudal System?
Political and social structure prevalent in Europe at the time of the Black Death
* Little opportunity for advancement
* Few people had everything, most had little
What did the Black Death do to the Feudal System?
Created vacant towns and farms (positions of authority need to be filled)
* Created new opportunities for the peasants
How was it discovered that Y. pestis caused the Black Death?
Analyzing genomes in the feet of bodies buried in London
Mid-19th Century Pandemic
* Date
* Cause
* Area
* Deaths
- 1850s, considered active until 1959
- Caused by Yersinia pestis
- Started in China, spread to US in 1900
- 12 million deaths in China and India alone
Pathogenesis of Yesinia pestis:
* Where does it live?
* What type of pathogen is it?
* Describe mechanism it transfers by
- Lives in rodents and are transmitted by fleas
- Zoonotic pathogen
Mechanism of transfer
* Causes “blocking” in the flea (biofilm formation in the proventriculus)
* Causes fleas to “starve”
* Fleas regurgitate bacteria into organisms it feeds on
What is the infective dose of Yersinia pestis?
~10 cells
* Very infective, many bacteria require hundreds of cells to cause infection
Where does Yersinia pestis initially survive and grow?
In innate immune cells
Where does Y. pestis replicate?
In lymphoid organs
* Spleen
* Bone marrow
* Lymph nodes
* Liver
What are buboes?
Swelling of lymph nodes
* Caused by Yersinia pestis
Y. pestis kills —- and continues to grow —–
- Macrophages
- Extracellularly
In the terminal stage of disease caused by Yersinia Pestis, what is the characteristic?
High concentrations of bacterial cells in blood
Why is the high concentration of bacteria in blood essential for transmission of Y. Pestis?
Fleas take blood meal (thus bacteria) and will transfer to other organisms when feeding
How does Y. pestis overcome immune defense mechanisms?
Can evade mammalian innate immune response
* Allows for infection prior to an immune response
What are the major virulence factors for Y. pestis?
- Type III secretion
- Phospholipase
- Plasminogen activator
- Yersiniabactin
- Mutated LPS
What is Type III secretion typical for?
Gram negative intracellular pathogens
What is phospholipase essential for in Y. pestis?
Survival in the flea
What is the purpose of the plasminogen activator in Y. pestis?
Clot buster
* Bursts clots to allow for spread of the bacteria (dissemination)
What is Yersiniabactin?
Iron binding siderophore
* Gets iron nutrient for the bacteria
What does a mutated LPS structure mean for Y. pestis?
The immune system cannot recognize the LPS structure, thus the excessive inflammation response occurs
How do Type III secretion systems work?
Secrete virulence factors (effectors) directly into host cells across host cell membrane
What are effectors? What is their function?
Virulence factors secreted in Type III secretion systems
* Function to ‘poison’ the host cell by targeting host cell signaling pathways
What did Y. pestis evolve from?
Y. pseudotuberculosis
True or False:
Y. pestis can survive in animal intestine
False, Y.pestis cannot survive well in the animal intestine
Why is the Y. pestis LPS molecule weakly recognized by the innate immune system?
A mutation in Lipid A modifying enzyme
What plasmid do all pathogenic Yersinia contain?
pYV
* Encodes type III secretion system
What are the 3 major forms of the Plague?
- Bubonic
- Septicemic
- Pneumonic
Bubonic Plague
* Transmission
* Signs/Symptoms
* Mortality
- Transmitted by flea bites
- Painfully swollen lymph nodes (“buboes”) in groin, armpits and neck
- 40-60% mortality if untreated
Which form of the plague is the most common?
Bubonic
What can bubonic plague develop into?
Septicemic and pneumonic plagues
Septicemic Plague
* Transmission
* Signs/Symptoms
* Mortality
- Fleas
- Presence of Y. pestis is systemic (in the blood)
- Experience gangrene and disseminated intravascular coagulation
- 50-90% mortality if untreated
Pneumonic Plague
* Transmission
* Signs/Symptoms
* Mortality
- Aerosols directly into lung, or from septicemic plague
- Coughing up blood
- 95-100% mortality if untreated
What is unique about pneumonic plague?
- Most dangerous
- Short incubation
- Treatment must be within first 24 hrs of symptoms for patient to survive
What are the 4 routes of transfer for human disease of Y. pestis?
- Flea bite
- Inhalation from humans/animals
- Handling infected animals (skin contact, scratch, bite)
- Ingesting infected meat
What is the most common route for human disease of Y. pestis?
Flea-bite
How does Y. pestis transmission occur historically and present-day?
Historically: Rat-borne urban epidemics
Present-day: Wildlife associated plague with sporadic outbreaks
What is done in diagnosis of Y. pestis?
- RAPID
- Culture and identification from bubo aspirate, sputum, blood may take 4 days
- Stains and rapid antigen tests (in endemic regions)
What is important in the treatment of pneumonic plague patients?
Isolation
* Very contagious and deadly
How is Y. pestis treated/prevented?
- Human cases treated with appropriate antibiotics including prophylaxis to exposed individuals
- Insecticides are used to kill fleas
What is Y. pestis identified as in the Centers for Disease Control and Prevention?
Category A
What defines a Category A organism?
- Can be easily disseminated or transmitted from person to person
- Result in high mortality rates and have the potential for major public health impact
- Might cause public panic and social disruption
Is Y. Pestis easy to grow?
Yes, only takes two days
