E. Coli Flashcards
What does E. Coli look like under the microscope?
Gram negative rods, found in GI tract of humans/animals.
What can E. Coli cause?
UTI, diarrhea, neonatal sepsis, intra-abdominal infections, nosocomial infections
How can E. coli cause infections if its a normal gut component?
If barriers are disrupted, or if virulence factors are acquired.
What happens when E. coli is plated w/lactose?
On a MacConkey plate, E coli changes the pH and causes a color change. Lactose is fermented.
O Antigen
LPS
H Antigen
Flagella
K Antigen
Capsule
Lower UTIs and symptoms
Cystitis (bladder), uretritis (urethra), dysuria and frequency.
Upper UTI and symptoms
Pyelonephritis, fever, flank pain, costovertebral angle tenderness, dysuria and frequency.
Most common cause of UTI?
E. coli.
What is the function of p-pili in E. coli?
Adhere to urinary epithelium. No P-pili, will flow out with urine.
Function of type 1 pili in E. coli?
Adhere to perineum.
How is pyelonephritis treated?
W/ ciprofloxacin or ceftriaxone (all IV)
How is cystitis/urethritis treated?
W/ ciprofloxacin or ceftriaxone (oral), or TMP-SMZ
Diarrhea causing strains of E. coli
ETEC (enterotoxigenic) EPEC (enteropathogenic) EIEC (enteroinvasive) EHEC (enterohemorrhagic) EAEC (enteroaggregative)
ETEC and virulence factors
Enterotoxigenic E. coli. Causes travelers diarrhea. Heat labile (AB exotoxin stims AC, cause Na, K secretion) and heat stable (stimulates GC, causes Cl, HCO3 secretion), no invasion. CF Pili cause adhesion. Come from a single plasmid.
EPEC and virulence factors
Enteropathogenic E. coli. Causes watery diarrhea in infants. Histologically = attachment/effacement lesion. Type III injection system introduces virulent proteins that trigger cytoskeleton rearrangements.
Where do the virulence genes come from for ETEC and EPEC?
ETEC (plasmid)
EPEC (Pathogenicity island [PAI])
EAEC
Enteroaggregative E. coli. Causes prolonged watery diarrhea in children. Stacked brick appearance and biofilm.
EHEC and sequella
Enterohemorrhagic. Shigatoxin (AB exotoxin that injured enterocytes and causes) Bloody diarrhea without a fever, progresses to hemolytic-uremic syndrome (HUS). Also causes microangiopathic anemia, thrombocytopenia, and renal failure(from shigatoxin). Acquired through raw beef, animal feces consumption, direct contact w/animals.
How to diagnose EHEC?
Look for shigatoxin in stool. Plate on sorbitol agar, O157:H7 causes clear colony formation
How does EHEC get shigatoxin gene?
From a phage.
EIEC
Enteroinvasive. Causes dysentery = small volume, bloody diarrhea, crampy abdominal pain, fever. Focus is in large intestine. Lots of WBC’s in stool. Bacterial invasion.
How to fix intraabdominal infections?
Surgery and medicine
What part of E. coli is responsible for neonatal sepsis? How to treat?
K1 capsular antigen. Cefotaxime and ampicillin
ESBLs
Extended spectrum betalactamases, can inactivate generations 1-3 ceph.
KPCs
Klebsiella pneumonia carbapenamases. Dangerous because carbapenems are treatment for ESBLs. Both occur in E. coli.
