18 - Shigella and E.Coli Flashcards
Pick one: Shigella are [lactose/non-lactose fermenters], [motile/non-motile] and [capsulate/noncapsulate].
Shigella is non-lactose fermenting, non motile and non-capsulate
What is the basis of shigella taxonomy?
O-antigen serotyping
What species of shigella is able to make a toxin?
Only S. Dysenteriae
Where is the only place Shigella is found? How is it transmitted?
Only human GI tract and transmitted through fecal oral route
True or false, shigella disease requires ingestion of a lot of bacterial particles because they are killed by the stomach acidity?
False, only 1-10 particles needed because they are particularly resistant to stomach acid
What are the two stages of shigellosis?
Stage 1 is in the small intestines while stage 2 is invasion of large intestines
True or false: Frequent stools, no pus and no blood, abdominal cramps, malaise, fatigue, anorexia, diarrhea and vomiting are ALL associated with shigellosis.
False. There is significant pus and blood. All other descriptors are correct
Shigella causes colonic ulceration. This is the route that they use to invade and cause cause their frequently occuring septicemia.Is that true or false?
False. They cause ulceration but rarely cause septicemia
In a laboratory setting, how would you distinguish salmonellosis from shigellosis?
You would need to culture / isolate the causative the bacteria
How does shigella invade adjacent colonic cells?
Lateral movement THROUGH the adjacent cells (i.e. pushes through into adjacent cell)
Again, what is the only sub type of shigella that makes toxin? What are the two main organ systems affected?
S. dysenteriae is the only subtype that makes shiga toxin. The toxin is neurotoxic and nephrotoxic
True or false: The major means of containing shigella to the gut is by antibody (IgA) in colonic mucosa?
False, it is contained by the innate immune system
Shiga toxin is nephrotoxic. How does it reach the kidneys to exert its toxic effects?
Through the circulation
What are the 2 major treatments for shigellosis?
Rehydration and antibiotics (the latter shortens the duration of disease by limiting shedding)
What are the 3 best practices highlighted in the notes for preventing spread of disease?
1) Good waste water treatment facilities, 2) handwashing and 3) healthy food handlers
How is the vaccine for shigella administered?
There is no vaccine
How would you distinguish e.coli from shigella on a McConkey plate? Why?
E.coli would be pink (vs. pale shigella) because of lactose fermentation
What are the 3 major antigens use to divide e.coli into serotypes?
O-, H- and K- antigens
What is the major means of distinguishing e.coli from other enterics?
By their biochemical profiles
True or false: E.coli are part of normal GI flora and are required for health
True
What are 4 extra-intestinal diseases associated with e.coli?
1) UTIs,
2) GI infections
3) Septicemia
4) neonatal menigitis
What are the 4 intestinal e.coli pathotypes?
Enteroinvasive (EIEC)
Enterotoxigenic (ETEC)
Enteropathogenic (EPEC)
Enterohemarrhagic (EHEC)
What e.coli pathotype produces disease essentially identical to shigellosis?
EIEC
Traveler’s diarrhea (abrupt onset but not invasive) that is endemic in developing countries is what e.coli pathotype?
ETEC
What are the 2 major virulence factors of enterotoxigenic e.coli?
Enterotoxin and colonization factors (CFAs)
What are the 2 possible subtypes of enterotoxin produced by ETEC?
Heat labile and heat stable
The heat labile toxin made by ETEC acts in a similar manner to cholera toxin. Why is disease less severe?
ETEC secrete toxin into periplasm, trapping it, therefore the toxin load that “gets to the host” is lower than in cholera
What is the proposed mechanism of heat stable enterotoxin?
Stimulation of guanylate cyclase
Why is it hard to make a vaccine to colonization factors of e.coli?
Many different antigenic types can mediate attachment to intestines
What is the e.coli pathotype that is associated with disease in young children living in developed countries? Does this cause disease in adults?
EPEC, it rarely causes disease in adults
Where is EPEC mainly found i.e what is it ingested from?
Undercooked meat products
What are the 2 EPEC virulence factors?
Bundle forming pili (BFP) and locus of enterocyte effacement (LEE)
Hemorrhagic (or non-hemorrhagic) colitis and hemolytic uremic syndrome is associated with what e.coli pathotype?
EHEC
What 2 groups of people are have increased risk of EHEC disease?
1) Young children and 2) children who get antibiotics
What is the most common e.coli diarrheal disease in developed countries?
EHEC
What are the 3 virulence factors of EHEC?
1) Bundle forming pili (BFP) 2) locus of enterocyte effacement (LEE) 3) shigatoxin (SLT)
What is the major means of toxin acquisition by the EHEC strains?
Lysogenization (phage integration into the bacterial DNA)
How can you differentiate majority of the EHECs from other e.coli pathotypes?
Most EHECs don’t ferment sorbitol
What e.coli pathotype is associated with UTIs in humans? How it transmitted?
UPEC, endogenously transmitted (from same host)
As UPECs ascent, what 4 disease / infections can they cause?
Urethritis, cystitis, nephritis, pyelonephritis
How can UPECs be diagnosed?
Greater than 100K CFU/ml in a clean urine catch
True or false: There is some level of selection for e.coli that preferentially colonize the GU tract.
True
What are 4 examples of virulence factors that UPECs have?
Adhesins, siderophores, toxins and capsules
What are the 2 most common causes of neonatal meningitis?
E.coli and Group B strep
True or false: Neonatal menigitis is associated with up to 40% mortality and up to 50% serious sequelae in survivors?
True
What is the specific capsule type found in greater than 75% of ecoli neonatal meningitis? What are its 2 main properties?
K1 capsule, it is antiphagocytic and anti-complement(ary)
Why is the K1 capsule antiphagocytic?
It is essentially sialic acid, therefore not immunogenic
What is the distinct toxin associated with 75% of ecoli septic shock w/ hemolysis?
RTX toxin
Under what conditions will a person be likely to get E.coli septic shock?
Underlying compromising condition (liver cirrhosis, following abdominal surgery, cancer patients)
How is e.coli septic shock managed? (2 things)
Antibiotics and supportive care
