E. Coli and Related Organisms Flashcards
(26 cards)
Describe some characteristics of E. Coli
- Gram negative or Positive?
- aerobic or anaerobic?
- where does it colonize? -
- what does it ferment?
- is it motile? how so?
- Gram negative
- Facultative anaerobe
- colonizes the Gut
- Ferments Glucose
- Very motile – flagella
Part of enterobacteriaceae family
What is the serotypic schmeme for ecoli?
- O antigen: polysaccharide at the distal end of the LPS
- H antigen: Flagellar antigen
- K antigen: capsule (not used any more)
What are the good guy (Dr. Jekyl) effects of e coli
_ majority of ecoli do not cause diseases
- colonize the gut;
produce helpful metabolites
Describe the classification of the disease causing types of E coli ?
Extra Intestinal (ExPEC)
- Uropathogenic
- MAEC - associated with neonatal meningitis
Diarrheagenic Strains: - ETEC - enterotoxigenic EHEC - Entero-hemorrhagic (and other STEC) EPEC -enteropathogenic EAEC -- enteroaggregative
what allows for the diverse profile of e coli?
Genomic Plasticity
- Bacteriophage
- conjugation (plasmids)
- Pathogenicity islands
What are the manifestations/presentation of Enterotoxigenic (ETEC)?
What symptom is notably absent
how long does it last?
How is it spread
- Common cause of travelers diarrhea and children diarrhea in 3rd world countries
Sx: Diarrhea, N, V, malaise,cramping
lasts 1 - 5days
NO FEVER
Spread by oral/fecal route; contaminated water supply (eg drinking tap water abroad)
What are the virulence factors of ETEC strains?
- Plasmid encoded Adherent Pili (23 different types)
- Heat labile enterotoxin
- heat stable enterotoxin
What is the mechanism for heat labile and heat stable enterotoxins ?
Heat Labile (same as cholera toxin):
- A/B Toxin. A is transported retrograde to the Golgi-
- ADP ribosylation of G protein
- Activation of AC —cAMP—PKA
- Phospho and opening of CFTR channel — chloride and water secretion = Diarrhea
Heat Stable Toxin:
- Analogous to Guanyline
- BInds G protein on apical surfface
Phospho and opening of CFTR
Treatment and Prevention of ETEC?
Prevention: use only bottled water and eat thoroughly cooked foods
Treatment: oral rehydration
Abx: FQs +/- immodium
- Rifaximine
Enteropathogenic (EPEC)
- Who gets this disease ?
- What are the manifestations?
- How is it transmitd
- Only infants contract the disease
Manifestations: short duration watery diarrhea, +FEVER + vomiting
Transmitted person to person
EPEC:
- virulence factors
- how does EPEC delay the immune response ?
- What proteins are endoced?
-
- LEE Pathogenicity Islands
- Bundle forming Pilus -
- Intimin
- Type 3 sections: TIR, NFkB suppression
- Type IV Pilus – allows for tighter binding of the bacteria to the host
- some effector proteins of the type 3 sections cleave NFkB or block its activation upstream
Treatment and Prevention of EPEC?
Prevention: Breast feed has been shown to protect
Treat: IV/Oral rehydration
Supportive care
Abx: possibly effective but the plasmids with the bundle forming pili genes also care resistances
Enterohemorrhagic (EHEC) and other Shiga toxin producing (STEC):
- Manifestations of disease (symptoms and complications)
- what symptom is notably absent?
- How is transmitted?
- Sx: cramps, pain, watery and blood diarrhea
NO FEVER (or mild fever)
- Hemolytic Uremic Syndrome:
TTP, microangiopathy, leading to renal failure - # 1 cause of renal failure in children
- Cattle are the most important reservoir, but also drinking water, petting zoos,
Diagnosis of EHEC
- what strain is associated with Outbreaks?
- what agar can be utilized to help diagnose this?
- what are other diagnositic test can be used?
- What are the findings of HUS
Agar: Sorbitol MacConkey –
- O157 H7: does not ferment sorbitol; does not turn pink
- ELISA for Shiga Toxin
PCR for toxin genes
HUS: TTP, Shistocytes; leading to kidney failure
describe Virulence Factors for EHEC (STEC)
what is the mechanism of the toxin?
- LEE pathogenicity Island: have genes for adherence
- Shiga Toxin (encoded for by bacteriphage)
- A/B toxin
- A removes adenine from 28S rRNA and stops protein synthesis
- Damage to endothelial promotes clotting – TTP and ischemia
:
What is unique about the use of ABX with EHEC Strains ?
DO NOT USE ABX FOR EHEC STRAINS
- induces SOS response from the cells which promotes the lytic phase of the bacteriophage
- further spread of the Shiga Toxin
Treatment / Prevention of EHEC/STEC strains
- Don’t eat pink ground beef
- OK to eat pink steak (inside is sterile)
- Avoid cross contamination
- Supportive care
Enteroaggregative (EAEC)
- manifestations
- how long does it last
- ## long term consequences
- Manifestions: watery diarrhea
- Childhood and traveler’s diarrhea
- Can be persistent
- Associated with growth retardation, poverty
Pathogenesis of EAEC
- Virulence Factors
-
Aggregative Adherence: (plasmid with pilus)
Toxins
- Pet – elicits fluid secretion
- EAST (Heat stable)
Extra Intestinal Pathogenic EC:
(ExPEC)
- what diseases are caused by these bugs?
- -
UTI
Neonatal Meningitis (MAEC)
Meningitis Associated EC (MAEC) –
- how is it obtained?
- What are some virulence factors?
- How is it treated
- common cause of meningitis is in neonates
- mothers are colonized by the bug and transmit it during delivery
- Child gets bacteremia
Virulence Factors: Capsule, Fimbriae, and able to cross the BBB
- Tx; 3rd Generation Cephalosporins
Klebsiella
- What is it’s primary virulence factor
- what can it cause?
- What is it resistant to?
- What is it sensitive to?
- Encapsulated
- UTIs, severe pneumonia, nosocomial infections
- Resistant to PCN
- Sensitive to cephalosporins (usually)
Enterobacter & Serratia
- Virulence Factors
- What can it cause
- what should you know about treating it?
- what works for treatment?
- Encapsulated
- Nosocomial infections; never really cause out patient infections
- Treatment: Cefepime or Carbapenem
- If sensitive: TMP/SMX; FQ
- inducible resistance to Cephalosporins (Cephalosporinases)
Proteus Mirabillis
- What is unique about its motility ? how does this appear on a plate? why does this complicate things
- What are other virulence factors?
- how is it treated
- Swarming Motility
- On culture, extends across the entire plate (unable to detect if infection is poly microbial)
- other virulence:
urease; Hemolysins, and fimbriae
Tx: ampicillin, 1st gen cephalosporins, TMP/SMX
