Enterobacteriaceae
Slackers Facts by Mike Ori
Disclaimer
The information represents my understanding only so errors and omissions are
probably rampant. It has not been vetted or reviewed by faculty. The source is our
class notes.
The document can mostly be used forward and backward. I tried to mark
questionable stuff with (?).
If you want it to look pretty, steal some crayons and go to town.
Finally…
If you’re a gunner, buck up and do your own work.
Enterobacteriacea characteristics
Rapidly growing large gram negative rods of
various sizes that can grow on plain agar both
aerobically or anaerobically.
Enterobacteriaceae antigens
O: outer membrane lipopolysaccharide
H: flagellar
K: cell surface polysaccharides
Enterobacteriacaea common pathogens
Escherichia
Shigella
Salmonella
Klebsiella
Yersinia
Enterobacteriaceae uncommon pathogens
Enterobacter
Serratia
Proteus
Morganella
Providencia
Most common Enterobacteriaceae species
Escherichia coli
Enterobacteriaceae dedicated pathogens
Shigella
Salmonella
E Coli type 1 pili characteristics
Pili that mediates general attachment to a wide
variety of epithelial cells via adhesins that
interact with host D-mannose residues
E. Coli P pili characteristics
Pili that interact with digalactose (gal-gal)
residues on uroepithelium thus allowing
efficient colonization of the urinary tract.
E. coli colonizing factor antigen (CFA) or bundle
forming pilin (BFP) characteristics
Pili that mediate attachment to enterocytes
E. Coli alpha hemolysin toxin
Pore forming exotoxin
Shiga toxin
Interferes with protein synthesis: An A-B toxin
secreted by E. coli whose active unit interferes
with protein synthesis by blocking the
ribosomal amino acyl tRNA binding site.
Causes hemolysis by unknown mechanisms.
Interferes with kidney function: Circulating toxin
binds renal tissues causing glomerular swelling
and the deposition of fibrin and platelets into
the microvasculature.
Labile toxin
Cholera-like A-B toxin generated by some E. coli
strains that increases cAMP production in host
cells by ADP-ribosylation of Gas
Stable toxin
Cholera-like (A-B?) toxin generated by some E.
coli strains that increases cGMP production by
host cells
E. Coli fancy smancy names
UPEC – uropathogenic EC
ETEC – enterotoxigenic EC
EPEC – enteropathogenic EC
EHEC – enterohemorrhagic EC
EIEC – enteroinvasive EC
E. Coli UTI causation %
90% of UTIs
UTI common patient
Sexually active women
E. Coli UTI pathogenicity factors
Type 1 pili mediate binding in periurethral area.
P pili mediate attachment to urogenital cells.
ETEC characteristics
Watery diarrhea caused by labile/stable toxins
with bacterial attachment facilitated by CFA
(colony factor antigen) pili. All of the above
are plasmid borne.
ETEC epidemiology
Significant cause of mortality in children 2 and
younger in less developed countries.
Common cause of traveler’s diarrhea. Human
reservoir.
Point to ponder: What kind of diarrhea would
the time traveler’s wife’s husband have?
ETEC symptoms
Watery diarrhea
EPEC characteristics
Bundle forming pili (BFP) bearing intimin protein
mediate attachment of the cells to host
enterocytes. Subsequent injection of E. coli
secretion proteins (Esp) causes the formation
of a pedestal by modifying the cytoskeleton.
Attachment and effacing lesion
Lesion caused by EPEC and EHEC E. coli strains
by injection of E. coli secretory proteins (Esp)
that results in the effacement of enterocyte
microvilli and the attachment of E. coli at the
top of pedestals formed from commandeered
cytoskeletal components.
Whats the coolest thing about intimin
E. coli injects the receptor for intimin along with
E. coli secretion proteins (Esp)
EPEC epidemiology
Common in less developed countries where it
accounts for 20% of the diarrhea in bottle fed
infants below 1 year of age.
EPEC symptoms
Watery diarrhea
EHEC characteristics
Resembles EPEC in that it creates attaching and
effacing lesions. Notably different however is
its secretion of shiga toxin.
EHEC symptoms
Bloody diarrhea and hemolytic uremic syndrome
EHEC epidemiology
More common in industrialized nations with
industrialized meat packing practices.
Outbreaks arise from undercooked meat and
cross contamination of produce.
EHEC inoculating dose
100-200 organisms
EHEC serotype
O157:H7
EPEC EHEC differences
EHEC elaborates shiga toxin.
EPEC prefers the small intestine
EHEC prefers the colon
EIEC characteristics
Virtually identical to shigella except that is has a
lower incidence of person to person
transmission.
Likes silent brooding types, strong chins, and
long walks on the beach.
EIEC epidemiology
Virtually restricted to children 5 or younger.
Humans are the only known reservoir.
ETEC and EPEC disease course
Self limiting watery diarrhea that clears within a
few days
EHEC timecourse
Initial watery diarrhea lasting 1-2 days followed
by intense abdominal pain and bloody
diarrhea that resolves in 3-10 days.
Hemolytic uremic syndrome symptoms
Occurs in EHEC cases primarily in children < 10
years old. Oliguria, edema, and palor followed
by hemolytic anemia, thrombocytopenia, and
renal failure.
EHEC culture diagnosis
Does not ferment sorbitol. Grow out on
MacConkey agar and then subject to O157
antisera.
EHEC treatment
Supportive care including hemodialysis and
hemapheresis if HUS is present (hooray for h).
Do not use abx or antimotility agents.
ExEC general guidelines
Supportive care is mainstay
Replace fluids with oral rehydration therapy or
IV if necessary.
Abx for ETEC, EIEC, EPEC but NOT for EHEC
Antimotility agents if you have to for EPEC and
ETEC but NOT for EIEC of EHEC
Shigella characteristics
Acid resistant (not acid fast) gram negative rod
transmitted by person to person contact
under conditions of poor sanitation which
causes disease that begins with watery
diarrhea and evolves into dysentery type
diarrhea.
Shigella species and types
Four species (A-D).
Group D has 38 antigenic types of O antigen
Shigella epidemiology
Spread by direct person to person contact under
conditions of poor personal or community
sanitation.
Small infecting dose of less than 200 organisms
insures efficient transmission.
The reservoir is human
S dysenteriae epidemiology
Largely limited to underdeveloped nations with
type 1 producing the most severe disease.
Shigella invasion target cells
Adherence to and transcytosis through M cells
to reach underlying phagocytic cells.
Invasin protein antigen (Ipa) function
Proteins injected into host cells by shigella using
a contact initiated injection system. These
proteins have a wide range of function
including cytoskeletal rearrangement, actin
polymerization, and apoptosis
Shigella intracellular movement mechanism
Moves via actin polymerization of host actin
filaments. Creates a characteristic actin
“comet” tail.
What other bacteria invades in a manner similar
to shigella
Listeria
Why is shigella so popular at parties? Because
its lysterical.
Shigella mucosal damage characteristic
Focal ulcers in the mucosa
Shigella diarrhea characteristics
Small volume stools containing WBC’s, RBC’s,
and bacteria.
Shigella toxin elaboration characteristics
Not all strains elaborate shigella toxin but doing
so correlates with disease severity. S
dysenteriae type 1 elaborates Stx.
If Stx is elaborated systemic effects of Stx can
occur as can HUS.
Shigella diagnosis
Labs routinely screen for shigella. No other
details were provided.
Shigella treatment
Generally self limiting however abx decrease
duration of disease and the contagious period.
Shigella clinical triad
Cramps
Tenesmus
Frequent small volume, bloody, mucoid
discharge
Salmonella characteristics
Gram negative facultative anaerobe with a wide
range of serovars based on O,H,K typing.
Disease for any given serovar may be
restricted to humans, animals, or both.
Salmonella food poisoning characteristics
Picnics, warm summer days, drunken coworkers, contaminated food, logarithmic
growth, You didn’t eat the potato salad did
you? You did? Damn! 2 day incubation, 3-4
days of suffering. See you next year.
Salmonella inoculating dose
10000 or more
Salmonella outbreak epidemiology
Cross contamination from poultry, exotic pets,
or humans particularly in the context of
modern industrial food plants.
Salmonella infection path
Cellular transcytosis to invade lamina propria
Salmonella cytoskeletal rearrangement pattern
Ruffling occurs within minutes of contact. This
results in pinocytosis of the bacterium.
Human only serovar of Salmonella
Typhi
What is a common carrier organ for typhi?
Gall bladders
Classic Victorian novel disease caused by typhi
Died of fever
Typhi disease cycle
• Invasion of mucosa
• Ingestion by macrophages but escape of killing
by interfering with oxidative burst/lysosome
fusion (??)
• Travel to secondary lymphoid tissues
• Rupture of macrophages
• Dissemination of bacteria
• Dissemination of LPS endotoxin resulting in
fever
Typhoid fever course
Resolution within about 3 weeks
Or
Death
Enteric fever cause
Disseminated Salmonella
Disseminated Salmonella sites
Osteomyelitis of long bones
Sepsis
Biliary tree (typhoid Mary?)
Salmonella diagnosis
Similar to shigella. Culture from blood early in
enteric fever.
Salmonella gastroenteritis treatment
Supportive care
Anti nausea and anti vomiting drugs
Do not use abx as these prolong carrier state
Enteric fever treatment
TMP-SMX or other abx to which the strain is
susceptible
Klebsiella characteristics
Polysaccharide encapsulated enterobacteriaceae
species that causes a classic lobar pneumonia.