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45 Cards in this Set

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true or false
all members of Enterobacteriaceace family have Endotoxins and are Gram Negative
True
Describe the antigenic structure of the Enterics family
K antigen (capsule): polysaccharide
H antigen (flagella): protein
O antigen (somatic): LPS (endotoxin)
what is an important characteristic that divides the family Enterobacteriaceae?
Lactose Fermentation
the rapid lactose fermenters of the Enterics family are:
Escherichia
Klebsiella
Enterobacter
what are the frank pathogens of the Enterics?
Salmonella, Shigella, Yersinia
where are the enterics usually found?
in or on man, in animals, on plants, and in soil and water
what do the Enterics do in the intestine?
synthesize vitamins and deconjugate bile acids
who are the slow non-lactose fermenters of the Enterics?
Proteus
Citrobacter
Serratia
Yersinia
Shigella
Salmonella
what can genetic exchange result in within the family of Enterics?
transfer of lactose fermentation to Salmonella
what does it mean for a enterotoxin to be cytotonic vs. cytotoxic
Cytotonic: causes changes in cellular activity
Cytotoxic: cause cell destruction
what are the organisms in the Enterics family that have enterotoxin activity?
E. coli
Salmonella
Shigella
Klebsiella
what correlates with decreased frequency of shock and death in gram negative bacteremia caused by the Enterics?
high titers of O-specific IgG in man correlates with decreased frequency of shock and death in gram negative bacteremia
Is E.coli a lactose fermenting microbe?
YES
what are the distinguishing characteristics of E. coli?
Gram Negative
Facultative aerobe
Non-spore forming
LACTOSE fermenting rod
since E.coli is part of the normal flora of the gut how does it cause disease?
when virulence factors are transfered to it from other Enteric family members
what are the virulence factors of E. coli?
1. Mucosal interactions
2. Exotoxin production: heat labile and stable toxin, shiga-like toxin
3. Endotoxin: Lipid A portion of LPS
4. Iron binding siderophore: obtains iron from human transferrin or lactoferrin
What type of disease is caused by E.coli with virulence factors?
Diarrhea
Urinary tract infection
Neonatal meningitis
Gram-negative sepsis
what type of E.coli causes "traveler's diarrhea"?
Enterotoxigenic E. coli.
affects the small intestine
watery diarrhea, cramps, nausea, vomiting, low grade fever
Plasmid mediated heat stable enterotoxins stimulate hypersecretion of fluids and electrolytes
what strain of E.coli causes Hemorrhagic Uremic Sydrome?
mostly caused by 0157:H7 E.coli
describe an infection of Enterohemorrhagic E.coli
affects large intestine
initial watery diarrhea followed by bloody diarrhea with abdominal cramps and NO fever may progress to hemolytic uremic syndrome (HUS)
what is the toxin responsible for Enterohemorrhagic E. coli?
mediated by cytotoxic Shiga toxins which disrupt protein synthesis > lesions with destruction of intestinal microvillus resulting in decreased absorption
what can be used to screen for E.coli?
sorbitol MacConkey (SMAC) media to screen and commercial antiserum on sorbital negative colonies
what does Proteus most commonly cause?
UTI
but can cause hospital acquired wound infections, septicemia, pneumonia in compromised host
Is Proteus a lactose fermenter?
NO
what is Proteus able to breakdown?
UREA producing urease
describe some distinguishing features of Proteus
Non-fastidious
Facultative anaerobe
bile tolerant
Alkaline pH
unpleasant odor
Highly motile
how do you differentiate between Proteus mirabilus and Proteus vulgaris?
P. mirabilus: indole -
P. vulgaris: indole +
what is it important to differentiate between Proteus infection and what other bacteria?
Rickettsia
this is done by mixing serum with Proteus strains to determine if there are antibodies in the serum that react with Proteus antigens. If these antibodies are present this suggest that the patient has been infected with Rickettsia
what is the 2d most common cause of neonatal meningitis?
E. coli (group B streptococcus is the first)
If you examine your patients urine and find: alkaline pH and suspect Proteus infection, what is this pH due to?
the Proteus ability to split urea into ammonia and cardon dioxide
an infection by the genus Serratia is most commonly found in:
compromised patients
what type of disease does Serratia cause in compromised patients?
Endocarditis
Bacteremia
Pulmonary
True or False
Serratia is typically quite resistant to antibiotics
TRUE
How is Serratia distinguished from other Enteric family members?
Motile
DNase
lipase
gelatinase resistant to colistin and cephalathin
what type of bacteria is chromogenic at room temperature?
Serratia
what are the organisms in the Enterics family that have enterotoxin activity?
E. coli
Salmonella
Shigella
Klebsiella
what correlates with decreased frequency of shock and death in gram negative bacteremia caused by the Enterics?
high titers of O-specific IgG in man correlates with decreased frequency of shock and death in gram negative bacteremia
Is E.coli a lactose fermenting microbe?
YES
what are the distinguishing characteristics of E. coli?
Gram Negative
Facultative aerobe
Non-spore forming
LACTOSE fermenting rod
since E.coli is part of the normal flora of the gut how does it cause disease?
when virulence factors are transfered to it from other Enteric family members
what are the virulence factors of E. coli?
1. Mucosal interactions
2. Exotoxin production: heat labile and stable toxin, shiga-like toxin
3. Endotoxin: Lipid A portion of LPS
4. Iron binding siderophore: obtains iron from human transferrin or lactoferrin
What type of disease is caused by E.coli with virulence factors?
Diarrhea
Urinary tract infection
Neonatal meningitis
Gram-negative sepsis
what type of E.coli causes "traveler's diarrhea"?
Enterotoxigenic E. coli.
affects the small intestine
watery diarrhea, cramps, nausea, vomiting, low grade fever
Plasmid mediated heat stable enterotoxins stimulate hypersecretion of fluids and electrolytes
what strain of E.coli causes Hemorrhagic Uremic Sydrome?
mostly caused by 0157:H7 E.coli
describe an infection of Enterohemorrhagic E.coli
affects large intestine
initial watery diarrhea followed by bloody diarrhea with abdominal cramps and NO fever may progress to hemolytic uremic syndrome (HUS)