Enterobacteriaceae - intro and E. coli Flashcards
Characteristics of Enterobacteriaceae (4)
Gram negative rods
LPS
Ferment glucose
oxidase negative
Serological typing
O Ag (polysaccharide portion of LPS)
K (capsular) Ag
H (flagella) Ag
Enterobacteriaceae with lac operon (lactose fermenting)
Klebsiella
Escherichia
Enterobacter
What is the common Ag?
Polyssaccharide core
What causes immune response?
Lipid A (endotoxin)
Most common cause of bacteremia?
E. Coli
Most common cause of GI tract infection?
Salmonella
Most common cause of UTI?
E. coli
Major cytokines induced by endotoxins
TNF alpha
IL-6
IL-1
Which virulence factor goes directly into host cell?
Type III secretion system
What fraction of bacteremia is caused by enterobacteriaceae?
1/3
What percent of bacteremia due to Enterobacteriaceae is due to E. coli? Klebsiella? Enterobacter?
45%
22%
20%
What percentage of UTI is caused by Enterobacteriacae?
70%
Diseases caused by E. coli
Gastroenteritis Hemolytic-uremic syndrome UTI Neonatal meningitis Septicemia
5 groups of E. coli that cause gastroenteritis
enterotoxigenic, enteropathogenic, enteroaggregative (SI)
Enteroinvasive, enterohemorrhageic (colon)
Enterotoxigenic E. coli (ETEC)
plasmid-mediated
non-invasive
Fimbrial adhesins, CFA I and II
Enterotoxins released by ETEC
Heat labile (LT) Heat stable (ST)
What is the cause of watery diarrhea due to ETEC
Enterotoxins cause iron channel to open, resulting in fluid secretions
does ETEC cause Inflammation? Fever?
No
No
Enteropathogenic E. coli (EPEC)
Non fibrial adhesion Moderately invasive Attachment-Effacement Bundle forming pilus Destruction of microvilli
What is the most significant thing about EPEC
Destruction of microvilli
no toxins produced
underdeveloped countries
Enterohemorrhagic E. coli (EHEC)
Moderately invasive
Shiga-like toxin /verotoxin
What does EHEC produce? What does it do?
Shiga-like toxin
cytotoxic to intestinal villi and colon epithelial cells
stops protein synthesis and causes necrosis
What is significant about diarrhea caused by EHEC?
Bloody
Is there inflammation with EHEC?
Yes - intense
Does EPEC cause inflammation? fever?
Yes - some
No fever
Enteroinvasive E. coli (EIEC)
nonfimbrial adhesions, omp
invasive
M cells
Large plasmid
no shiga toxin
Characterize diarrhea caused by EIEC
dysentery -
mucous, bloody
EIEC cause inflammation? Fever?
Yes, yes
Enteroaggregative E. coli (EAggEC)
no adhesins - GVVPQ fimbriae
noninvasive
“Biofilm”
Produce ST-like toxin and alpha hemolysin
no fever
What is different about diarrhea caused by EAggEC?
Chronic/persistent diarrhea in children without immunizations
(non bloody)
Common cause of UTI
E. coli
80% community acquired) (40% hospital - Abx resistance common
Community- acquired UTI are _____ infections
ascending
What are some bacterial attributes/host factors that cause UTI?
Bacterial: P fimbriae (pilus), urease, hemolysins
Host: short urethra in women, catheterization, compromised immunity etc
Virulence factors of Uropathogenic E. coli
P fimbria - pyelonephritis associated pili (PAP pili)
binds P blood group Ag with D-galactose-D-galactose residue
Treatment of enteric pathogen
fluid replacement is the main thing. don’t want dehydration
infection control in hospital
Abx therapy requires test for sensitivity to avoid resistance
