Enterobacteriaceae

1
Enterobacteriaceae family of mostly intestinal
inhabitants Gram-negative rods distinguished
by motility differences metabolic
characteristics lactose fermentation,
indole production serology DNA
homology Virotyping Serotyping based
on variable surface antigens
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Serotyping based on variable surface antigens O
antigin of LPS H antigen of flagella O
serogroup - correlation with virulence H
serotype 0111 H4 0111 H12
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Escherichia coli 1940s 1950's - cause of
diarrhea in hospital nurseries cause of
other diseases hemolytic uremic syndrome
bladder and kidney infections septicemia
4
Four or five types of strains similar
properties, different mechanisms Enteropathogenic
EPEC - diarrhea no enterotoxin Enterotoxigeni
c ETEC Enteroinvasive EIEC - dysentery
penetrate epithelium Enterohemorrhagic EHEC -
hemorrhagic colitis, bloody diarrhea Enteroaggr
egative EAggEC - similar to ETEC
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Virulence factors Lippolysaccharide Pilus -
loose binding Intimin - tight
binding Enterotoxins (in ETEC)
heat-labile toxin LT - two types LT-I,
LT-II LT-I similar to cholera toxin fluid and
electrolyte loss by cells - diarrhea
heat-stable toxin ST shiga-like toxin (SLT
in EHEC, strain 0157H7) intense inflammatory
disease cause of bloody diarrhea? Virulence
factors encoded on phage antibiotic use may
induce lytic cycle phage spread to other
enterics
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EPEC bind to mucosal cells prevent reabsorption
of water ETEC adhere to small intestine
mucosa secrete toxins that cause
diarrhea accompanied by vomiting and fever may
be fatal in infants and young children travelers
diarrhea
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EPEC attach to mucosa and clump microvilli in
area of clumps gone adjacent microvilli
elongated bacteria more invasive, cause
inflammatory response cell invasion and
alteration cause diarrhea EHEC disease similar
to Shigella dysentery intense inflammatory
response complication acute kidney disease
hemolytic ureminic syndrome bacteria attach to
mucosa secrete enterotoxins - bloody diarrhea
8
EIEC no toxin identical to dysentery
invade cells and spread laterally
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Transmission fecal - oral route 0157H7 -
colonize cattle farm animals source of
contamination of meat grinding mixes with
the meat Prevention proper sanitary
procedures hand washing critical antibiotic
s not recommended except in chronic cases
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Other infections 25 of nosocomial UTI 8 of
surgical site infections urinary and bladder
85 non-hospital acquired cases bacterial
prostatitis - 80of cases pyelonephritis - 90
of cases
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Enterobacter similar to E.coli ferments
lactose to acid gas some strains produce
enterotoxin like E.coli Diseases
nosocomial UTI - 5 surgical infections -
7 nosocomial pneumonia - 11 Source
found in IV fluids
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Klebsiella pneumoniae similar to E.coli
ferments lactose to acid and gas Infections
nosocomial UTI - 8 - from catheters
pneumonia - 9 - inhalation equipment
bacteremia - 5 - IV equipment Proteus does not
ferment lactose urease-positive NH4 produces
precipitates Mg Ca as urinary
stones motile hydrogen sulfide
produced Infections nosocomial UTI and surgery
infections
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Coliform and Proteus nosocomial UTI -
46 surgical infections - 24 bacteremia -
17 pneumonias - 30 all nosocomial infections
- 29 Problems in IV fluids Resistant to
antiseptics and disinfectants Plasmid encoded
virulence factors transferred to other
strains
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Serratia lactose fermenter antibiotic
resistant Infections nosocomial UTI
bacterial sepsis and endotoxic shock
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Salmonella lactose not fermented motile urease
negative DNA homology with E.coli -
90 Infections gastroenteritis and
typhoid fever
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Salmonella Virulence factors Adhesins not
known bacteria attach - alter cell
membrane ruffling Invasins - induce
engulfment Survival factors - prevent
destruction in phagocytes LPS - cause of
most symptoms of typhoid fever
inflammatory response during mucosal invasion
cause of abdominal pain and fever
inflammatory damage to mucosal cells cause of
diarrhea
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Prevention proper food handling educate
pubic vaccines - 3 available prevent
attachment and invasion of mucosa Treatment self
-limiting, antibiotics not needed S.
typhimurium - may go systemic need treatment to
prevent endotoxic shock S.typhi need
treatment in acute cases need treatment for
carriers clear bacteria from liver and bile
duct
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Shigella non-motile no hydrogen sulfide
S.dysenteriae shigellosis, dysentery, bacillary
dysentery acute infectious enteritis syndrome
frequent, small volume bloody stool
abdominal cramps, rectal pain
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Shiga toxin acts as enterotoxin - fluid
loss acts as neurotoxin - ? acts as cytotoxin
(tissue culture cells) Shigella virulence
factors adhesins - attach to mucosa Shiga
toxin may cause hemolytic uremic syndrome
causes blood vessel damage, maybe kidney
damage enhances effect of LPS
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Shigella - sequence of events (model
studies) bacteria attach bacteria enter mucosal
cells move laterally mucosal cells die
intense inflammatory response
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Shigella Prevention clean water
supply avoid water, ice, vegetables, salad
washed with water avoid items chilled in
ice Note flies spread
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Shigella 140 million cases annually 0.5 million
die side effects - Reiters Syndrome
arthritis following intestinal infection
also seen with some other bacterial infections
autoimmune response caused by bacterial
antigens inflammation of joint tissue
23
Erwinia motile facultative anaerobe catalase
positive associated with plants, some plant
pathogens Plant diseases blights,
cankers leaf spots wilts soft rot, including
fruits and vegetables