Enterobacteriaceae Flashcards
List the four unvarying characteristics of the family Enterobacteriaceae:
- Are they gram neg or pos (+ what shape)?
- Do they ferment glucose?
- Do they reduce nitrate to nitrite?
- Are they oxidase pos or neg?
- Facultative Gram-Neg rods
- Ferment glucose
- Reduce nitrate to nitrite
- Oxidase negative
Where are Enterobacteriaceae found in the wild?
Indigenous flora of GI tract
Name 3 important antigens of Enterobacteriaceae and where they are located.
- H-antigen (located in peritrichous flagella)
- K-antigen (located in capsule (important in causing extraintestinal colonization, UTI, and invasive disease))
- O-antigen (of LPS)
What Enterobacteriaceae ferment lactose and which don’t? (just read)
- Non-lactose fermenters: Salmonella Shigella Proteus Yersinia - Ferment lactose: E. coli Klebsiella Enterobacter Citrobacter Serratia
What is the habitat of Enterobacteriaceae Genus Escherichia (main e.g. E coli)
Intestines of humans and animals
- We get it at birth
What does the presence of E coli in water indicate?
Fecal contamination
Is E coli gram neg or pos?
Gram-neg
What clinical syndromes are a/w E. coli?
- Gram negative sepsis
- UTIs (80% of community acquired UTIs)
- Wound infections
- PNA in IC hospitalized patients
- Meningitis in neonates
- Gastroenteritis
*Name the 5 types (+ 1 important subtype) of E coli that cause gastroenteritis.
- Enterotoxigenic E. coli (ETEC)
- Enteropathogenic E. coli (EPEC)
- Enteroinvasive E. coli (EIEC)
- Enterohemorrhagic E. coli (EHEC)
- Shiga Toxin producing E. coli (STEC) - Enteroaggregative E. coli (EAggEC)
Main signs/sx of Enterotoxigenic E. coli (ETEC)?
Profuse watery diarrhea
e.g. in Mexico
Main signs/sx of Enteropathogenic
E. coli (EPEC)?
- Occurs in infants
- Diarrhea w/o gross blood
Main signs/sx of Enteroinvasive E. coli (EIEC)
Blood, mucus, and many leukocytes in stool
Main signs/sx of Enterohemorrhagic E. coli (EHEC)?
Bloody diarrhea without WBCs.
- In STEC, may progress to hemolytic uremic syndrome (HUS).
Main signs/sx of Enteroaggregative E. coli (EAggEC).
Watery diarrhea with blood and mucus.
What is the commonly ID’d serotype of shiga toxin E coli?
How is it transmitted?
- E. coli 0157
- Undercooked meat, veggies
- Also thru person-to-person contact
What demo’s are at increased risk for hemolytic uremic syndrome (HUS) a/w E coli 0157?
Young children and elderly
- Retarded people
What’s another name for hemolytic uremic syndrome (HUS) a/w E coli 0157?
What do the onset sx look like?
Hemorrhagic colitis
- Bloody watery diarrhea, abd cramps
- No significant fever
- Absence of WBC in stool
*List the triad of symptoms that defines hemolytic uremic syndrome (HUS).
- Acute renal failure
- Thrombocytopenia
- Hemolytic anemia (schistocytes)
Does E coli enter the blood?
No, just shiga toxin
*Explain by shiga toxin causing HUS leads to - acute renal failure, thrombocytopenia and hemolytic anemia.
Shiga attaches to endothelial cells. The highest conc of receptors are in the renal endothelium, so this is where the dmg occurs bleeding, scar formation
- Scars forming on endothelium, lumen narrow, leading to schistocyte formation and loss of Hb (hemolytic anemia)
- Dmg and bleeding @ endothelium: clotting occurs, platelets used (thrombocytopenia)
- Eventually blood supply to kidney becomes narrower (acute renal failure)
What is causing bloody diarrhea in HUS?
Toxins → Damage of microcirculation → vasculitis → mucosal damage. Infarction of mucosa leads to bleeding into the bowel and bloody diarrhea
What was another E coli strain that lead to a flour recall this year?
E. coli 0121
In lab dx of E coli, when should you collect specimen?
From what type of sample?
- 1st 4 days onset (any enteric illness); before abx
- Whole stool
What is the special type of plate used to ID E. coli 0157?
Sorbitol MacConkey Agar
rather than lactose
