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MLSP 6211: Enterobacterales and ID

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Posted on 
May 22nd, 2023
Home economics MLSP 6211: Enterobacterales and ID
question

Enterobacterales can be described as

answer

ubiquitous

-free-living in soil, water, sewage, vegetation

question
Normal microbiota in GI tract except
answer
salmonella, shigella, and yersina
question
Enterobacteriaceae include
answer
Escherichia, Klebsiella, Citrobacter, Enterobacter, Klebsiella, and Salmonella
question
Hafniaceae include
answer
Edwardsiella, Hafnia
question
Morganellaceae include
answer
Morganella, Providencia, Proteus
question
Yersiniaceae include
answer
Serratia and Yersinia
question
Erwiniaceae include
answer
pantoea
question
Enterobacterales reservoirs
answer

-environmental

-zoonotic

-human carrier

-health care and community-acquired

-endogenous

question

What opportunistic infections are enterobacterales the cause of

answer

-UTI

-Bacteremia, Septicemia, Neonatal sepsis

-Pneumonia

-Wounds

-Meningitis

question
What enterobacterales are considered true pathogens
answer

-Salmonella, Shigella, Yersinia

-Specific strains of E. coli

-Yersinia pestis

question
What are the family characterisitics
answer

-GNB/GNCB

-Facultative anaerobes

-Ferment glucose

-Oxidase negative

-Non-spore forming

-Catalase +

question

Many of the Enterobacterales reduce

answer
nitrate to nitrite
question
Most Enterobacterales are motile at
answer
37 C
question
Which Enterobacterales are not motile
answer
Shigella, Klebsiella, Yersinia, and Proteus (swarming)
question
What is the typical colony morphology on SBA
answer

large, moist, gray

-most hemolytic

question
Which species is beta hemolytic
answer
Escherichia coli
question
What are the most useful tests to begin the ID of Enterobacterales
answer

-carbohydrate fermentation

-morphology on selective/differential

-Indole

-H2S production

-TSI slant

question
What are the common definitive ID methods
answer

-Urea

-Citrate

-PDA

-MR/VP

question
What does the cell wall contain in this group?
answer

-Thin PG layer (stains pink)

-LPS

question
What is LPS composed of
answer

- O polysaccharide

-Core polysaccharide

-Lipid A

question

Lipid A

answer

endotoxin and contributes to the virulence of the organism

-released upon death

question
What do Enterobacterales that are encapsulated look like
answer
The colony will appear mucoid
question
Chromosomally mediated fimbriae
answer
adherence to host receptors
question
Plasmid mediated pili
answer

sex pili

-genetic transfer between bacteria

question
What are the factors of pathogenicity
answer

-LPS

-Capsule

-Adhesins

-Exotoxins

-Hemolysins

question
Pathogenicity of LPS
answer

-activates complement

-release cytokines

-leukocytosis

-Thrombocytopenia

-DIC

question
Pathogenicity of capsule
answer
resist phagocytosis; interfered with antibodies binding to cell
question
What are the three antigens involved in epidemiological classification
answer

-O antigen

-K antigen

- H antigen

question
What antigen does all the enterobacterales possess
answer
O antigen
question
What is another characterisitc does a enterobacterales possess if they posses the K antigen
answer
a capsule
question
How can a K antigen be removed
answer

by boiling for 30 min

-exposes the O antigen for typing

question
K1 antigen
answer
Escherichia coli
question
Vi antigen
answer
Salmonella enterica
question
Organisms with the H antigen also have
answer
flagella
question
How are most enterobacterales treated
answer
-antibiotic therapy
question

Klebsiella has intrinsic resistance to

answer

ampicillin

question

Enterobacter has intrinsic resistance to

answer
Ampicillin and Cephalosporins
question
How is Extended Spectrum Beta-lactamase mediated
answer
Plasmid-mediated
question
Which species are prone to ESBL
answer

-E. Coli

-K. pneumoniae

-K. oxytoca

question
What does ESBL include
answer

-carbapenemases

-caphalosporinases

-metallo-beta-lactamases

question
Carbapenem-resistant Enterobacteriaceae
answer

-typically healthcare settings

-life threatening

-plasmid transmission

question
How do you report CRE
answer

-resistant to carbapenems

-resistant to other beta-lactams

question
On MAC, organisms that ferment lactose produce
answer
acid that change the indicator in the agar to pink
question
Organisms that do not ferment lactose
answer
do not change the indicator color and appeaer colorless/brown
question

What does E. coli produce on EMB

answer
a metallic sheen
question
Moderately selective agars inhibit
answer
many of the LF GNB (e.coli) and normal flora of GI tract
question

Hektoen agar

answer
detect lactose, sucrose fermentation
question
HE agar: fermenter
answer
yellow/orange
question
HE agar: non-fermenter
answer
colorless; no color change
question
HE agar: H2S production
answer
blackening of colony
question
Highly selective agar
answer

inhibit almost all GNB except Samonella

-used for outbreaks

question
Selective broths
answer
keepp most bacteria in lag phase, allowing select isolates to grow in log phase
question
What is the gram stain of enterobacterales
answer
GNB
question

What are the enzymatic tests used

answer
oxidase, indole, urease, and citrate
question
What are the metabolic tests used
answer
MR-VP, amino acid degradation, carbohydrate fermentation and oxidation
question
Oxidase test
answer
bacteria rubbed onto filter paper inoculated with oxidase reagent
question
Oxidase +
answer
purple
question
Oxidase negative
answer
no color change
question
Indole test
answer
bacteria rubbed onto filter paper inoculated with Enrlich indole reagent or Ehrlich DMACA
question
Indole +
answer
green
question

Indole negative

answer
no color change
question
What is the alternative reagent for indole
answer

Kovac's reagent

pink= +

question
Urease
answer

enzyme hydrolyzes substrate urea into ammonia, water, CO2

question
Urease +
answer
magenta pink
question
Citrate test
answer
detect citrate-permease that converts citrate to pyruvate; pyruvate may enter metabolic cycle
question
Citrate +
answer
growth or blue color (pH change)
question
Citrate negative
answer
no change (green)
question
ONPG
answer
Detect beta-galactosidase that hydrolyzes substrate ONPG; determines ability to ferment lactose whether rapidly or slowly
question
ONPG +
answer
yellow (true lactose fermenter)
question

ONPG negative

answer
no color produced (no lactose fermentation)
question
Carbohydrate fermentation
answer
various carbohydrate broths inoculated with organism; acid production turns indicator a color
question
O/F test
answer
two carbohydrate broths inoculated with organism; one overlaid with oil, one not overlaid with oil
question
Closed tube O/F
answer
closed tube for fermentation
question

Open tube O/F

answer
open tube for oxidation
question
O/F both yellow
answer
fermenter
question
O/F open tube only yellow
answer
oxidizer
question
O/F no color change in both tubes
answer
nonsaccharolytic
question
Amino acid degradation
answer
enzymes deaminate, dehydrogenate or decarboxylate various amino acids resulting in pH change
question
Phenylalanine (PDA)
answer
deaminate phenylalanine to phenylpyruvic acid
question
Methyl red
answer
detect mixed acid production from glucose fermentation; pH change
question
Voges Proskauer
answer
detect neutral bi-products of glucose fermentation
question
Motility test
answer
detect motility by presence of flagella
question
Wet mount motility
answer

aerobes

-inoculate broth, incubate, observe microscopically for motility

question
Semi-solid medium motility
answer

facultative anaerobes

-stab agar

question
Positive semi-solid motility
answer
movement away from stab line
question
H2S detection
answer

sodium thiosulfate reduced to H2S

-causes blacking of the agar

question
Cetrimide test
answer
detects the ability of the organism to grow in the presence of cetrimide
question
Cetrimide is selective for
answer
Pseudomonas aeruginose
question
Nitrate reduction test
answer
ability of organism to reduce nitrate to nitrite
question
TSI test
answer
detects fermentation, gas production, and H2S
question
A pH change in the TSI indicates
answer
the fermentation of one or more sugars
question

How is gas production demonstrated

answer

bubbles or cracks

question
How is H2S production indicated
answer
blackening of the agar
question

Multitest systems

answer
automated and manual; combination of enzymatic, metabolic, carbohydrate fermentation; reference database
1 of 94
question

Enterobacterales can be described as

answer

ubiquitous

-free-living in soil, water, sewage, vegetation

question
Normal microbiota in GI tract except
answer
salmonella, shigella, and yersina
question
Enterobacteriaceae include
answer
Escherichia, Klebsiella, Citrobacter, Enterobacter, Klebsiella, and Salmonella
question
Hafniaceae include
answer
Edwardsiella, Hafnia
question
Morganellaceae include
answer
Morganella, Providencia, Proteus
question
Yersiniaceae include
answer
Serratia and Yersinia
question
Erwiniaceae include
answer
pantoea
question
Enterobacterales reservoirs
answer

-environmental

-zoonotic

-human carrier

-health care and community-acquired

-endogenous

question

What opportunistic infections are enterobacterales the cause of

answer

-UTI

-Bacteremia, Septicemia, Neonatal sepsis

-Pneumonia

-Wounds

-Meningitis

question
What enterobacterales are considered true pathogens
answer

-Salmonella, Shigella, Yersinia

-Specific strains of E. coli

-Yersinia pestis

question
What are the family characterisitics
answer

-GNB/GNCB

-Facultative anaerobes

-Ferment glucose

-Oxidase negative

-Non-spore forming

-Catalase +

question

Many of the Enterobacterales reduce

answer
nitrate to nitrite
question
Most Enterobacterales are motile at
answer
37 C
question
Which Enterobacterales are not motile
answer
Shigella, Klebsiella, Yersinia, and Proteus (swarming)
question
What is the typical colony morphology on SBA
answer

large, moist, gray

-most hemolytic

question
Which species is beta hemolytic
answer
Escherichia coli
question
What are the most useful tests to begin the ID of Enterobacterales
answer

-carbohydrate fermentation

-morphology on selective/differential

-Indole

-H2S production

-TSI slant

question
What are the common definitive ID methods
answer

-Urea

-Citrate

-PDA

-MR/VP

question
What does the cell wall contain in this group?
answer

-Thin PG layer (stains pink)

-LPS

question
What is LPS composed of
answer

- O polysaccharide

-Core polysaccharide

-Lipid A

question

Lipid A

answer

endotoxin and contributes to the virulence of the organism

-released upon death

question
What do Enterobacterales that are encapsulated look like
answer
The colony will appear mucoid
question
Chromosomally mediated fimbriae
answer
adherence to host receptors
question
Plasmid mediated pili
answer

sex pili

-genetic transfer between bacteria

question
What are the factors of pathogenicity
answer

-LPS

-Capsule

-Adhesins

-Exotoxins

-Hemolysins

question
Pathogenicity of LPS
answer

-activates complement

-release cytokines

-leukocytosis

-Thrombocytopenia

-DIC

question
Pathogenicity of capsule
answer
resist phagocytosis; interfered with antibodies binding to cell
question
What are the three antigens involved in epidemiological classification
answer

-O antigen

-K antigen

- H antigen

question
What antigen does all the enterobacterales possess
answer
O antigen
question
What is another characterisitc does a enterobacterales possess if they posses the K antigen
answer
a capsule
question
How can a K antigen be removed
answer

by boiling for 30 min

-exposes the O antigen for typing

question
K1 antigen
answer
Escherichia coli
question
Vi antigen
answer
Salmonella enterica
question
Organisms with the H antigen also have
answer
flagella
question
How are most enterobacterales treated
answer
-antibiotic therapy
question

Klebsiella has intrinsic resistance to

answer

ampicillin

question

Enterobacter has intrinsic resistance to

answer
Ampicillin and Cephalosporins
question
How is Extended Spectrum Beta-lactamase mediated
answer
Plasmid-mediated
question
Which species are prone to ESBL
answer

-E. Coli

-K. pneumoniae

-K. oxytoca

question
What does ESBL include
answer

-carbapenemases

-caphalosporinases

-metallo-beta-lactamases

question
Carbapenem-resistant Enterobacteriaceae
answer

-typically healthcare settings

-life threatening

-plasmid transmission

question
How do you report CRE
answer

-resistant to carbapenems

-resistant to other beta-lactams

question
On MAC, organisms that ferment lactose produce
answer
acid that change the indicator in the agar to pink
question
Organisms that do not ferment lactose
answer
do not change the indicator color and appeaer colorless/brown
question

What does E. coli produce on EMB

answer
a metallic sheen
question
Moderately selective agars inhibit
answer
many of the LF GNB (e.coli) and normal flora of GI tract
question

Hektoen agar

answer
detect lactose, sucrose fermentation
question
HE agar: fermenter
answer
yellow/orange
question
HE agar: non-fermenter
answer
colorless; no color change
question
HE agar: H2S production
answer
blackening of colony
question
Highly selective agar
answer

inhibit almost all GNB except Samonella

-used for outbreaks

question
Selective broths
answer
keepp most bacteria in lag phase, allowing select isolates to grow in log phase
question
What is the gram stain of enterobacterales
answer
GNB
question

What are the enzymatic tests used

answer
oxidase, indole, urease, and citrate
question
What are the metabolic tests used
answer
MR-VP, amino acid degradation, carbohydrate fermentation and oxidation
question
Oxidase test
answer
bacteria rubbed onto filter paper inoculated with oxidase reagent
question
Oxidase +
answer
purple
question
Oxidase negative
answer
no color change
question
Indole test
answer
bacteria rubbed onto filter paper inoculated with Enrlich indole reagent or Ehrlich DMACA
question
Indole +
answer
green
question

Indole negative

answer
no color change
question
What is the alternative reagent for indole
answer

Kovac's reagent

pink= +

question
Urease
answer

enzyme hydrolyzes substrate urea into ammonia, water, CO2

question
Urease +
answer
magenta pink
question
Citrate test
answer
detect citrate-permease that converts citrate to pyruvate; pyruvate may enter metabolic cycle
question
Citrate +
answer
growth or blue color (pH change)
question
Citrate negative
answer
no change (green)
question
ONPG
answer
Detect beta-galactosidase that hydrolyzes substrate ONPG; determines ability to ferment lactose whether rapidly or slowly
question
ONPG +
answer
yellow (true lactose fermenter)
question

ONPG negative

answer
no color produced (no lactose fermentation)
question
Carbohydrate fermentation
answer
various carbohydrate broths inoculated with organism; acid production turns indicator a color
question
O/F test
answer
two carbohydrate broths inoculated with organism; one overlaid with oil, one not overlaid with oil
question
Closed tube O/F
answer
closed tube for fermentation
question

Open tube O/F

answer
open tube for oxidation
question
O/F both yellow
answer
fermenter
question
O/F open tube only yellow
answer
oxidizer
question
O/F no color change in both tubes
answer
nonsaccharolytic
question
Amino acid degradation
answer
enzymes deaminate, dehydrogenate or decarboxylate various amino acids resulting in pH change
question
Phenylalanine (PDA)
answer
deaminate phenylalanine to phenylpyruvic acid
question
Methyl red
answer
detect mixed acid production from glucose fermentation; pH change
question
Voges Proskauer
answer
detect neutral bi-products of glucose fermentation
question
Motility test
answer
detect motility by presence of flagella
question
Wet mount motility
answer

aerobes

-inoculate broth, incubate, observe microscopically for motility

question
Semi-solid medium motility
answer

facultative anaerobes

-stab agar

question
Positive semi-solid motility
answer
movement away from stab line
question
H2S detection
answer

sodium thiosulfate reduced to H2S

-causes blacking of the agar

question
Cetrimide test
answer
detects the ability of the organism to grow in the presence of cetrimide
question
Cetrimide is selective for
answer
Pseudomonas aeruginose
question
Nitrate reduction test
answer
ability of organism to reduce nitrate to nitrite
question
TSI test
answer
detects fermentation, gas production, and H2S
question
A pH change in the TSI indicates
answer
the fermentation of one or more sugars
question

How is gas production demonstrated

answer

bubbles or cracks

question
How is H2S production indicated
answer
blackening of the agar
question

Multitest systems

answer
automated and manual; combination of enzymatic, metabolic, carbohydrate fermentation; reference database

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