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Unit 6: Enterobacteriaceae Flashcards

1
Q

What characteristics distinguish the Enterobacteriaceae from other gram negative rods?

A

Oxidase negative, glucose fermenters, reduce nitrate

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2
Q

What four genera are VP positive?

A

Klebsiella, Serratia, Hafnia and Enterobacter

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3
Q

What three genera are nonmotile?

A

Shigella, Klebsiella and Yersinia (at 35 degrees)

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4
Q

What pathogens are we routinely looking for when culturing a stool specimen.

A

E coli 0157, Shigella, Y. entercolytica and Salmonella

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5
Q

Explain how you would serotype an isolate which identified as a Salmonella species using the API system.

A

Somatic O agglutination

If S. typhoid is suspected, Vi agglutination as well

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6
Q

Proteus, Providencia, and Morganella are all positive for what test? (this test helps distinguish these genera from other Enterobacteriaceae)

A

PDA

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7
Q

Serratia species are distinguished from most other Enterobacteriaceae by being positive for what test?

A

Gelatinase and DNase

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8
Q

Name the two most commonly isolated Klebsiella species. How are the two differentiated?

A

K. pneumoniae- Indole NEG

K. oxytocin’s- Indole POS

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9
Q

What species of Shigella is ONPG positive?

A

S. sonnei (group D)

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10
Q

Give the KIA reaction for Salmonella typhi.

A

K/A H2S weak positive, gas positive

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11
Q

What organism resembles E. coli except for its H2S reaction?

A

E. tarda

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12
Q

What organism swarms on blood agar?

A

Proteus, both species

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13
Q

What tests will aid in the identification of Yersinia enterocolitica?

A

TSI

its A/A and the KIA is K/A bc it is sucrose positive

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14
Q

What enrichment broth is used for the isolation of GNBs, especially Salmonella and Shigella?

A

Gram-negative broth

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15
Q

What enrichment broth is selective for Salmonella spp?

A

Selenite broth

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16
Q

What are the 4 enteric antigens? include location and heat labile/stable

A

O antigen- in the cell wall; somatic, heat stable
H antigen- flagellar; heat labile
K antigen- in capsule; heat labile
Vi antigen- in capsule S. typhi, heat labile

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17
Q

Polyvalent applies to which enteric antigen

A

O antigen

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18
Q

Polyvalent agglutination for Salmonella

A
  • Based on common somatic O antigens
  • Heat stable
  • detects 95% of human Salmonella species, Serogroups A-E1
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19
Q

Vi agglutination for Salmonella typhi

A
  • Based on Vi antigens
  • Heat labile
  • Detects S. typhi based on O antigens AND Vi antigens
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20
Q

Group A-D agglutination for Shigella

A
  • Based on somatic O antigens
  • Heat labile
  • Serogroups A-D
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21
Q

KIA result A/A mean what?

A

Glucose fermented anaerobically and lactose fermented aerobically

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22
Q

What is different about TSI agar?

A

Contains sucrose as well as lactose

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23
Q

What is an ONPG positive result?

A

yellow

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24
Q

What are slow fermenters missing?

A

permease

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25
Nitrate reduction positive result
Red or colorless AFTER addition of Zinc
26
What is a positive indole result?
Kovac's= red | Spot indole=blue
27
What is the citrate utilization test testing for?
Use of Sodium citrate as only carbon source and inorganic ammonium dihydrogen phosphate as sole fixed nitrogen source
28
What are the pH indicators in the decarboxylate test? How do they work?
Bromcresol purple- turns purple when alkaline Cresol red- turns yellow when acidic
29
PDA positive result?
Greenish brown color
30
Gelatinase positive result?
Black
31
What are the 4 E coli strains that cause gastroenteritis?
Enterotoxigenic E coli (ETEC) Enteropathogenic E coli (EPEC) Enteroinvasive E coli (EIEC) Enterohemorrhagic E coli (E coli 0157)
32
What media is used to recover Enterohemorrhagic E coli (E coli 0157)?
MacConkey with Sorbitol agar Ecoli0157 is nonfermenter
33
Enterotoxigenic E coli (ETEC): common name, source and symptoms
Travelers diarrhea Contaminated food and water Watery stool
34
Enteropathogenic E coli (EPEC): source and symptoms
Hospital acquired, often seen in infants | Mucoid stool, no blood
35
Enteroinvasive E coli (EIEC): symptoms
Destroys epis, blood stool
36
Enterohemorrhagic E coli (E coli 0157): source and symptoms
Undercooked beef and anything unpasteurized Bloody stool, no WBCs Can result in Hemolytic-uremic syndrome (HUS)
37
What about Shigella makes it a bigger concern?
Very low colony count needed for infection | Resistant to gastric acid
38
4 serogroups of Shigella?
A- S. dystenteriae B- S. flexneri C- S. boydii D- S. sonnei Dirty fingers bring shigella
39
What type of infections are seen with Edwardseilla?
-Extra intestinal infections | -
40
What are the two Citrobacter species of importance?
C. freundii and C. koseri
41
Which genus causes infection in immunocompromised patients at any level?
Klebsiella
42
What are the two Klebsiella species of importance?
K. pneumoniae and K. oxytoca
43
What are the two Enterobacter species of importance?
E. aerogenes and E. cloacae
44
Which genus causes the strong smell of feces?
Hafnia
45
What organism resembles E. coli except for its VP reaction?
Hafnia
46
What is concerning with Serratia?
Anti-microbial susceptibility changes fast
47
What are the two Protius species of importance?
P. mirabilis and P. vulgaris
48
Which genus is commonly seen in nursing homes?
Providencia
49
What are the two Providencia species of importance?
P. rettgeri and P. stuartii
50
Why and how does haemophilus need to be ruled out with Yersinia?
Yersinia can be coccobacilliary but it can grow on MAC
51
What media is selective and differential for Y. entercolitica?
CIN agar
52
Which Yersinia species is nonmotile at room temp?
Y. pestis
53
What organism's colony morphology resembles beaten copper?
Y. pestis
54
What organism is found in water fowl?
Y. pseudotuberculosis
55
Which Yersinia grows in cold temps?
Y. enterocolitica
56
How do you differentiate the two Enterobacter species?
E. aerogenes : L, O= POS A=NEG E. cloacae: A, O=POS L= NEG
57
What biochemical test/result separates Hafnia from the rest of Klebsiella tribe?
Citrate NEG
58
What 2 biochemical test/result separate Klebsiella from the rest of Klebsiella tribe?
Urease POS and Motility NEG
59
What 5 biochemical test/results are shared among all of Klebsiella tribe?
``` VP POS ONPG POS Gas POS on KIA PDA NEG H2S NEG ```
60
What other 3 biochemical test/results are shared among all of the PDA positive organisms?
Motility POS ONPG NEG KIA K/A
61
What biochemical test/result separates Proteus from the other PDA positive organisms?
H2S POS
62
How do you differentiate the two Proteus species?
``` P. mirabilis: Orinthine Decarboxylation POS Indole NEG Gelatinase NEG P. vulgaris: All decarboxylation NEG Indole POS Gelatinase POS ```
63
What biochemical test/result separates Morganella from the other PDA positive organisms?
Citrate NEG
64
How do you differentiate the two Providencia species?
P. stuartii: Urease NEG/pos | P. rettgeri: Urease: POS
65
Which genuses are PDA AND VP negative?
``` Citrobacter Edwardsiella Escherichia Shigella Salmonella Yersinia ```
66
What biochemical test/result separates Shigella from the other PDA/VP NEG organisms?
Negative motility at all temps (except Yersinia)
67
How could you distinguish Y. pests from Shigella?
Shigella A-C: ONPG NEG and Y. pestis is POS | S. sonnei: Ornithine decarboxylation POS and Y. pestis is all NEG
68
What biochemical test/result separates E. coli from the other motile PDA/VP NEG organisms?
H2S NEG
69
What biochemical test/result separates E. tarda from the other PDA/VP NEG with molity and H2S POS organisms?
Citrate NEG
70
What biochemical test/result separates Citrobacter from Salmonella?
Citrobacter: Lysine Decarb NEG | Salmonella Lysine decarb POS
71
What organisms are confirmed via commercial ID?
Salmonella | Providencia spp.
72
What biochemical test/result separates Shigella from Salmonella?
Salmonella: Citrate, H2S and Motility POS

Microbiology (11 decks)

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