Salmonella and Shigella Flashcards
Gram negative rod enterobacteria: what 3 species could they be?
Salmonella, Shigella, E Coli
What are some specific bacterial surface elements that differentiate serotypes?
O antigens, H antigens, K antigens
Causes typhoid fever
Salmonella Typhi
Salmonella strain that causes gastroenteritis
S. cholerasuis and S. enteriditis/typhimurium
2 salmonella strains that cause bacteremia
S. Typhi and S. Cholerasuis
1 Salmonella strain that does NOT cause bacteremia
S. Enteriditis/Typhimurium
Salmonella strain that possesses Vi capsule
S. Typhi
Salmonella strain that has incubation period of 7-14 days
S. Typhi
Salmonella strain that is most common in US
S. Enteriditis/Typhimurium
Sal strain that may be asymptomatic with a + stool culture
S Typhi
Salmonella strain that can colonize the gallbladder
S. Typhi
In general, LPS in the blood can cause what 2 clinical features?
fever, shock
Why can S. Typhi cause a + stool culture, then a + blood culture, then a + stool culture again?
Intially it is found in the GI system, then it goes into the bloodstream, and it can get into the gallbladder from there and re-enter the GI system.
SPI 1 and SPI 2 stand for what?
Salmonella Pathogenicity Island 1 and 2
SPI 1 encodes genes for what?
Invasion of the gastric epithelial cells
SPI 2 encodes genes for what?
Intracellular survival
Describe Type 3 Secretion Systems (T3SS)
secretion where a protein moves across the bacterial cytoplasmic and outer membrane AND across the host cell membrane via an injection needle
What bacterial species have T3SS?
Salmonella, E Coli, Shigella
Which species of salmonella have SPI1 and SPI2?
S Typhi, S Cholerasuis.
Whaty type of immune system reaction will be caused by LPS/endotoxin?
Innate. Macrophages will be activated, release TNF-alpha into tissue, increased plasma proteins, phagocytes and lymphocytes increase in tissue.
What can happen when gram-negatives grow in the bloodstream? what bacteria is most likely to cause this?
Endotoxic shock; S typhi
During an S Typhi infection, what tests are likely to isolate the bacterium?
week 1: stool. Week 2: Blood. Week 3: stool.
For which strain of salmonella would abx be used?
S typhi, and S. enteriditis/typhimurium IF patient is immunocompromised.
which Salmonella strain is primarily found in contaminated water sources?
s typhi
Are there vaccines available for any strains of salmonella?
YES 2 vaccines for S typhi: oral attenuated and Vi capsular polysaccharide.
what is the incubation period for S cholerasuis? what is the infectious dose?
6-72 hours. 1000 organisms
what is the likely clinical course of a S cholerasuis infection?
gastroenteritis followed by bacteremia and high fever
the origin of which salmonella strain is swine?
S cholerasuis
what is the most common salmonella infection in the US?
S enteriditis / S typhimurium
If salmonella is found on strawberries, eggs, or peanuts, what type is it likely to be?
S enteriditis / S typhimurium
How long will clinical symptoms of S enteriditis / S typhimurium take to appear?
8-48 hours
Do S enteriditis / S typhimurium have T3SS? Do they have SP1 and SP2?
Yes, No, No
For all salmonella infections, what cultures would be most likely to yield bacteria?
All: feces. S typhi/S Cholerasuis: blood.
Does salmonella ferment lactose?
No
Does salmonella ferment glucose?
yes
Does salmonella produce H2S?
yes
Is salmonella motile?
yes, has a flagellum
Salmonella: cytochrome oxidase positive or negative?
negative.
How could you determine whether various salmonella outbreaks were connected?
comparing O and H antigens and serotyping
How is shigella spread?
Food, Fingers, Feces, Flies
Which shigella is most common in the developing world?
Shigella dysenteriae
Which shigella is most common in the US?
Shigella sonnei
Does shigella have an animal reservoir?
no
Does shigella have LPS? how do we know?
YES. because it is gram-neg.
what about shigella causes diarrhea and abd cramps?
Shiga toxin.
how common is bacteremia due to Shigella?
rare
what is a common clinical finding with shigella?
blood diarrhea with mucus
how long will shigella be detected in feces post-recovery?
1-4 weeks
Incubation period for shigella?
1-4 days
What is the inoculum level for shigella?
100 bugs
Describe the Shiga toxin itself
exotoxin with 2 subunits. Subunit A interferes with function of the 60S rRNA, inhibiting protein synthesis. Subunit B binds to the receptor on intestinal cells
Does Shigella ferment glucose?
yes, does not produce gas
does Shigella ferment lactose?
no
Shigella: motile?
no. Shigellum no flagellum.
what antigens does shigella have?
O and K only; no flagellum –> no H antigen
Do shigella and salmonella produce H2S?
Salmonella yes, shigella no
Name the members of Enterobacteriaciae.
E Coli, Shingella, Salmonella
Generally, 3 clinical profiles caused by Salmonella?
typhoid, bacteremia, gastroenteritis
What is the infectious dose for S Typhi?
10^3 to 10^5 bacteria
How many pathogenicity islands does S typhi have?
2
Features of endotoxic shock?
fever, diarrhea, hypotension, DIC
Distinct diagnostic feature of typhoid fever/S typhii?
rose spots
How would we prevent S typhi?
sanitation (access to clean water) and vaccination (2 types available)
What does a positive cytochrome oxidase test look like?
purple
Oxidase test is positive for what bacteria?
other common Gram negative pathogens such as Pseudomonas and Neisseria
Salmonella: indole positive or negative? urease positive or negative?
Indole negative, urease negative
shigella: indole positive or negative? urease positive or negative?
Indole negative, urease negative
How does shigella lead to apoptosis of cells and ulceration? and subsequent bloody, mucusy stool?
Has Shiga toxin with A/B subunits. Cause cell death by preventing protein synthesis (via 60S ribosome inhibition) so cells die –> ulceration, mucous, blood.
4 ways to distinguish Salmonella from Shigella?
- Salmonella has flagellum, Shigella does not
- Sal contains O and H antigens, Shigella only O (no flagellum)
- Both ferment glucose, but Shigella does not produce gas with fermentation
- Shigella does not produce H2S gas
