E. Coli & Related Organisms Flashcards
What are major serotypes of E. Coli and what are the antigens for?
O serotype - side chain of LPS
H serotype - flagellin
What is ETEC?
Enterotoxigenic E. coli
What is EPEC?
Enteropathogenic E. coli
What is EHEC?
Enterohemorrhagic E. coli
What is EAEC?
Enteroaggregative E. coli
What is ExPEC?
Extraintestinal E. coli
What are the clinical symptoms of ETEC?
Watery diarrhea (travelers!)
What are the virulence factors of ETEC?
Pili (aka Colonization Factor Antigens)
Heat-labile enterotoxin
Heat-stable enterotoxin
What other toxin is the heat-labile enterotoxin of ETEC similar to?
Cholera toxin
Works in same way (ADP ribosylated of G protein -> adenylate cyclase -> increased cAMP -> PKA -> phosphorylates CFTR -> chloride pumped out and water follows)
What is treatment for ETEC?
Oral rehydration
Shorten duration with fluoroquinolone
What is clinical presentation of EPEC?
Watery diarrhea and vomiting in infants in developing countries
What are virulence factors for EPEC?
Bundle-forming pillus
Attaching and effacing Type III secretion system on LEE pathogenicity island
- Tir and intimin
What is treatment for EPEC?
Breast feeding is protective
Oral rehydration
Antibiotics not effective
What is clinical presentation of EHEC?
Watery, bloody diarrhea
Hemorrhagic colitis
Hemolytic-uremic syndrome
How is EHEC transmitted?
All comes back to cattle!
What are the virulence factors of EHEC?
Shiga toxins
Attaching and effacing Type III secretion system on LEE pathogenicity island
What is the mechanism of Shiga toxin?
Depurinates 28S rRNA, stopping protein synthesis
Cell death occurs and forms clots on cell
Why can’t you give antibiotics to treat EHEC?
INCREASES SHIGA TOXIN PRODUCTION
Induces an SOS response that causes phage production and therefore toxin production
What category of E. Coli does O157:H7 fall into?
EHEC
What is the difference between typical v. atypical EPEC?
Atypical does not have bundle forming pilus
What is the treatment for EHEC?
Avoid uncooked cattle things
DO NOT GIVE ANTIBIOTICS
How can O157:H7 be diagnosed?
MacConkey sorbitol agar plate, O157:H7 will not ferment on the plate but other strains will
What is clinical presentation of EAEC?
Diarrhea with mucous (also travelers)
Associated with growth retardation
What are virulence factors of EAEC?
Pili (aggregative adherence)
Cytotoxins
What is clinical presentation of ExPEC?
Most common cause of UTI in sexually active women
Can cause Neonatal meningitis
What are virulence factors of ExPEC that causes neonatal meningitis?
K1 capsule
S fimbriae
Cellular invasion
What is the treatment for ExPEC neonatal meningitis?
3rd generation cephalosporins (Ceftriaxone, Ceftazidime)
What is clinical presentation of Klebsiella?
Pneumonia
UTI
What is treatment for Klebsiella?
Treat based on resistance, usually sensitive to cephalosporins
But always resistance to penicillins!
How do Klebsiella, Enterobacter and Serratia appear when plated?
Encapsulated and mucoid
What is treatment for Enterobacter and Serratia?
Has inducible resistance to cephalosporins!! Don’t use them even if it says sensitive!!
Use penicillin, carbapenem, fluoroquinolone
What is clinical presentation of Proteus?
UTIs, espec with catheters
What are virulence factors of Proteus?
Urease (causes stone formation and protease stays in stone)
Swarming motilty
What is treatment for Proteus?
Usually sensitive to penicillins
But unusual among GNB since resistant to tigecycline and polymixin!
