35 - Bacterial Infections of the GI Tract III Flashcards
What is vibrio spp?
A bacteria that causes a non-inflammatory infection of the small intestine
There are three different types of this bacteria
What are the three different types of Vibrio spp.?
- Vibrio cholerae*
- Vibrio parahaemolyticus*
- Vibrio vulnificus
What does vibrio cholerae cause?
Gastroenteritis and bacteremia
What does vibrio parahaemolyticus cause?
Gastroenteritis, bacteremia and wound infections
What does vibrio vulnificus cause?
Bacteremia and wound infections
What are the characteristics of Vibrio spp. bacteria?
- Gram negative
- Facultative anaerobes
What living conditions can Vibrio spp. bacteria survive under?
They can live…
- Freely in water
- Under a broad temperature range
- Under a wide range of pH
Although they are able to survive in a wide range of pH, what is important to know about this?
They actually are susceptible to the low pH in the stomach, so you need a large dose of the bacteria (10^9) in order for enough to survive the stomach in order to cause disease in the small intestine
What is one thing that Vibrio spp. REQUIRE in order to live and grow?
Sodium chloride (NaCl)
What disease does Vibrio cholerae cause?
Cholera
- Can range anywhere from asymptomatic to severe watery diarrhea
How long is the incubation period for vibrio cholerae?
2-3 days
How long will symptoms of Vibrio cholerae last?
Up to 7 days
What percent of affected individuals will develop severe symptoms?
5-25% of infected individuals will develop SEVERE watery diarrhea
What are the symptoms of this severe case?
- Abrupt onset
- A LOT of water… Gallons per day of diarrhea
- “Rice water” stool
Can cholera be fatal?
Yes the severe dehydrationn can kill within hours
How does Vibrio cholerae spread?
Easily spreads through contaminated water
Example: the Broad street pump in London in 1854
Is cholerae a world-wide infection?
Yes… It is an important cause of diarrheal disease in the developing world
Is there any long-term immunity associated with infection?
Yes - this appears to be O antigen specific immunity
What are cholera outbreaks typically associated with?
- Natural disaster
- Population displacement
- Poor sanitary conditions
How many cholera pandemics have there been?
7 documented pandemics… We are still currently in the 7th
What are the “biotypes” of the cholera toxins that have caused the 7 pandemics?
- Pandemics 1-6 were all caused by the classic biotype
- The current pandemic (7) is caused by the “El Tor” biotype
What are the different biotypes of cholera toxins named after?
The type of O1 cholera toxin they produce
What are the features of the current El Tor biotype cholera toxin?
- It is LESS severe than the classic biotype
- Longer duration of carrying the disease compared to the classic biotype
- El Tor survives better in the environment
How many affected individuals with the El Tor biotype show severe symptoms?
Not very many…
- 1 severe case for every 30-100 severe cases
- Many less affected individuals show severe symptoms compared to the classic biotype
What happened to the El Tor biotype in 1992?
It acquired a new O antigen, becoming serotype O139 and caused a major epidemic that spread through India and other endemic countries for a decade
What is the pathogenesis of vibrio cholerae?
The toxin is co-regulated by a pilus (“bridge”) for adhering to intestinal epithelial cells
What kind of toxin is the cholera toxin?
An AB toxin
What does the toxin do once it is inside the host cell and active?
- Activates adenylate cyclase
- Increases cAMP
- Causes a massive efflux of watery secretions
Does the cholera toxin cause cell damage?
No
What type of bacterial toxin is the cholera toxin very similar to?
The ETEC LT toxin (traveler’s diarrhea)
It is very similar in structure and function
How is the cholera AB toxin encoded in the bacteria?
On a prophage
A prophage is a bacteriophage (often shortened to “phage”) genome inserted and integrated into the circular bacterial DNA chromosome or existing as an extrachromosomal plasmid
How do you diagnose vibrio cholerae?
Culture
- Use a differential media
- This would only be done in places where cholera is not common
How do you treat vibrio cholerae?
Rehydration therapy - IV and oral
- This is very important to prevent fatality from diarrhea
- Without rehydration therapy, mortality rate can be as high as 90%
What type of a bacteria is Vibrio parahaemolyticus?
Another Vibrio spp. bacteria, but this one is INFLAMMATORY
What type of disease does Vibrio parahaemolyticus cause?
- Explosive watery diarrhea
- Nausea
- Vomiting
- Abdominal cramps
- Low grade fever
What virulence factor does Vibrio parahaemolyticus have?
Kanagawa hemolysin
This induces chloride secretion thus causes watery diarrhea
What is Vibrio parahaemolyticus most commonly associated with?
The consumption of raw shellfish
Vibrio parahaemolyticus is the most common cause of two widespread illnesses. What are they?
- Bacterial gastroenteritis in Japan and Southeast Asia
- Seafood associated gastroenteritis in the US (Alabama, Mississippi, Florida, etc.)
How do you treat Vibrio parahaemolyticus?
It is self-limiting, so no intervention is necessary
How do you prevent Vibrio parahaemolyticus?
Proper cooking of shellfish
What is Yersinia enterocolitica?
- An inflammatory bacteria
- Gram negative coccobacilli
- The is related to the causative agent of the bubonic plague
Is Yersinia enterocolitica common or rare?
Common
- Widespread in nature and animals
Are most isolates of Yersinia enterocolitica virulent or avirulent?
Avirulent
How does Yersinia enterocolitica spread’?
By the ingestion of contaminated water or food
Example: improperly cooked pork
What are the symptoms of Yersinia enterocolitica?
- Fever
- Abdominal cramps
- Watery, bloody diarrhea
How long will the symptoms of Yersinia enterocolitica last?
1-2 weeks
Describe the pathogenesis of Yersinia enterocolitica
Poorly understood
- It appears as if Yersinia enterocolitica binds to and invades M-cells in the terminal ileum (similar to salmonella spp.), but by a different mechansim