E. Coli Flashcards
General characteristics of enterobacteriacea
Salmonella and E. Coli
Gram (-) rods
Catalase (+)
Oxidase (-)
Facultative anaerobes
Ferment glucose and sugars
- grows on MacConkey agar*
- e. Coli = pink
- salmonella = yellow/gold
e. coli specifically ferments lactose
E. Coli specific characteristics
“Travelers diarrhea”
- very closely related to shigella
Characteristics:
- a-hemolytic
- motility
- lactose fermentation
- imdole (+)
- Methyl red (+)
- citrate (-)
- sulfate (-)
- urease (-)
Strains that cause enterocolitis are not normal flora, but some strains are normal flora
EMB agar
Eosin-methylene blue agar
- grows e.coli specifically with blue-black colonies with metallic green shine
E. Coli stereotypes
Based on O, H and K antigens
O = somatic LPS H = flagella protein K = polysaccharide capsule
Pathogenesis of e. Coli virulence factors
Capsular polysaccharides
- make e. Coli slippery and difficult to phagocytosis
LPS
- are lipid A polysaccharides that produce endotoxins. This is the primary cause of shock and sepsis symptoms
Fimbrial adhesions
- allows attachment to mucosal and epithelial surfaces
Enterotoxin/shigatoxin
- causes cytotoxic and necrotizing effects
- main toxins that are secreted into the blood stream
Enterotoxigenic E. Coli (ETEC)
“Travelers diarrhea” strain
- community-acquired in areas with poor sanitation
Causes watery non-bloody diarrhea
- very common in children <5 yrs
- comes from the LT/ST toxin secretions
- NO inflammation or invasion of tissues
Enteroinvasive E. Coli (EIEC)
“Dysentery” form
Causes necrosis and inflammation of the intestinal epithelium since it actually invades and lysis vacuoles in the intestinal cells
Causes watery, bloody diarrhea.
- diarrhea also has mucus and leukocytes in it
Attaching and Effacing E. Coli (AEEC)
Forms actin pedestals (strong attachment) by attaching to the host cell actin. Then “effaces” host microvilli
Induces premature enterocyte exfoliation and encodes for intimin and TIR
- intimin= keeps host cell attached no matter what
Has two subset forms
- EPEC (enteropathogenic)
- STEC (shiga toxin)
EnteroPathogenic E. Coli (EPEC)
A subset of AEEC
“Infantile diarrhea” form
- infects children <2 the most often
Symptoms
- profuse and persistent diarrhea
- vomiting and fever
- dehydration (can be fatal if not kept in check)
Shiga Toxin E. Coli or EnteroHemorrhagic E. Coli (STEC)/(EHEC)
Is a subset of AEEC
- includes O157:H7
“Shiga toxin and hemolytic-uremic syndrome form”
- causes dysentery
- causes renal failure in pediatric patients if not fixed
- can induce hemolytic-uremic syndrome after 2 weeks of infection
What is Hemolytic-uremic syndrome (HUS)
Classic triad of the following
- anemia
- thrombocytopenia
- Acute kidney damage and decreased renal blood flow due to micro thrombi
Enteroaggregative E. Coli (EAEC)
A type of travelers diarrhea, but not the most common one
- that being said it is very common in United States
Forms aggregate colonies/biofilms on top of cells and seeps cytotoxin and enterotoxins into cells/blood stream
Can be acute or chronic and is exceptionally dangerous to HIV patients
E. Coli adhesions and the pathotype they are associated with.
EAF = EPEC
AA fimbriae = EAEC
Intimin = EPEC
Actin pedestals = AEEC
Toxins seen in e. Coli
Enterotoxins
Heat-labile (LT)
Endotoxins (LPS)
Heat-stabile (ST)
Heat-labile toxin
Exotoxins that are secreted by bacteria that are related to cholera
LT1: overactivates cAMP and induces hypersecretion of fluids
- watery diarrhea
- associated with K88 adhesions
- secreted by ETEC
LT2: overactivates cAMP
- induces watery diarrhea
- secreted by ETEC
