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Microbiology > Unit 6: Enterobacteriaceae > Flashcards

Unit 6: Enterobacteriaceae Flashcards

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Biology 101 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
Q

Nitrate reduction positive result

A

Red or colorless AFTER addition of Zinc

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26
Q

What is a positive indole result?

A

Kovac’s= red

Spot indole=blue

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27
Q

What is the citrate utilization test testing for?

A

Use of Sodium citrate as only carbon source and inorganic ammonium dihydrogen phosphate as sole fixed nitrogen source

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28
Q

What are the pH indicators in the decarboxylate test? How do they work?

A

Bromcresol purple- turns purple when alkaline

Cresol red- turns yellow when acidic

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29
Q

PDA positive result?

A

Greenish brown color

30
Q

Gelatinase positive result?

A

Black

31
Q

What are the 4 E coli strains that cause gastroenteritis?

A

Enterotoxigenic E coli (ETEC)
Enteropathogenic E coli (EPEC)
Enteroinvasive E coli (EIEC)
Enterohemorrhagic E coli (E coli 0157)

32
Q

What media is used to recover Enterohemorrhagic E coli (E coli 0157)?

A

MacConkey with Sorbitol agar

Ecoli0157 is nonfermenter

33
Q

Enterotoxigenic E coli (ETEC): common name, source and symptoms

A

Travelers diarrhea
Contaminated food and water
Watery stool

34
Q

Enteropathogenic E coli (EPEC): source and symptoms

A

Hospital acquired, often seen in infants

Mucoid stool, no blood

35
Q

Enteroinvasive E coli (EIEC): symptoms

A

Destroys epis, blood stool

36
Q

Enterohemorrhagic E coli (E coli 0157): source and symptoms

A

Undercooked beef and anything unpasteurized
Bloody stool, no WBCs
Can result in Hemolytic-uremic syndrome (HUS)

37
Q

What about Shigella makes it a bigger concern?

A

Very low colony count needed for infection

Resistant to gastric acid

38
Q

4 serogroups of Shigella?

A

A- S. dystenteriae
B- S. flexneri
C- S. boydii
D- S. sonnei

Dirty fingers bring shigella

39
Q

What type of infections are seen with Edwardseilla?

A

-Extra intestinal infections

-

40
Q

What are the two Citrobacter species of importance?

A

C. freundii and C. koseri

41
Q

Which genus causes infection in immunocompromised patients at any level?

A

Klebsiella

42
Q

What are the two Klebsiella species of importance?

A

K. pneumoniae and K. oxytoca

43
Q

What are the two Enterobacter species of importance?

A

E. aerogenes and E. cloacae

44
Q

Which genus causes the strong smell of feces?

A

Hafnia

45
Q

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

A

Hafnia

46
Q

What is concerning with Serratia?

A

Anti-microbial susceptibility changes fast

47
Q

What are the two Protius species of importance?

A

P. mirabilis and P. vulgaris

48
Q

Which genus is commonly seen in nursing homes?

A

Providencia

49
Q

What are the two Providencia species of importance?

A

P. rettgeri and P. stuartii

50
Q

Why and how does haemophilus need to be ruled out with Yersinia?

A

Yersinia can be coccobacilliary but it can grow on MAC

51
Q

What media is selective and differential for Y. entercolitica?

A

CIN agar

52
Q

Which Yersinia species is nonmotile at room temp?

A

Y. pestis

53
Q

What organism’s colony morphology resembles beaten copper?

A

Y. pestis

54
Q

What organism is found in water fowl?

A

Y. pseudotuberculosis

55
Q

Which Yersinia grows in cold temps?

A

Y. enterocolitica

56
Q

How do you differentiate the two Enterobacter species?

A

E. aerogenes : L, O= POS
A=NEG
E. cloacae: A, O=POS
L= NEG

57
Q

What biochemical test/result separates Hafnia from the rest of Klebsiella tribe?

A

Citrate NEG

58
Q

What 2 biochemical test/result separate Klebsiella from the rest of Klebsiella tribe?

A

Urease POS and Motility NEG

59
Q

What 5 biochemical test/results are shared among all of Klebsiella tribe?

A 
VP POS
ONPG POS
Gas POS on KIA
PDA NEG
H2S NEG
60
Q

What other 3 biochemical test/results are shared among all of the PDA positive organisms?

A

Motility POS
ONPG NEG
KIA K/A

61
Q

What biochemical test/result separates Proteus from the other PDA positive organisms?

A

H2S POS

62
Q

How do you differentiate the two Proteus species?

A 
P. mirabilis: Orinthine Decarboxylation POS
                    Indole NEG
                    Gelatinase NEG
P. vulgaris: All decarboxylation NEG
                   Indole POS
                   Gelatinase POS
63
Q

What biochemical test/result separates Morganella from the other PDA positive organisms?

A

Citrate NEG

64
Q

How do you differentiate the two Providencia species?

A

P. stuartii: Urease NEG/pos

P. rettgeri: Urease: POS

65
Q

Which genuses are PDA AND VP negative?

A 
Citrobacter
Edwardsiella
Escherichia
Shigella
Salmonella
Yersinia
66
Q

What biochemical test/result separates Shigella from the other PDA/VP NEG organisms?

A

Negative motility at all temps (except Yersinia)

67
Q

How could you distinguish Y. pests from Shigella?

A

Shigella A-C: ONPG NEG and Y. pestis is POS

S. sonnei: Ornithine decarboxylation POS and Y. pestis is all NEG

68
Q

What biochemical test/result separates E. coli from the other motile PDA/VP NEG organisms?

A

H2S NEG

69
Q

What biochemical test/result separates E. tarda from the other PDA/VP NEG with molity and H2S POS organisms?

A

Citrate NEG

70
Q

What biochemical test/result separates Citrobacter from Salmonella?

A

Citrobacter: Lysine Decarb NEG

Salmonella Lysine decarb POS

71
Q

What organisms are confirmed via commercial ID?

A

Salmonella

Providencia spp.

72
Q

What biochemical test/result separates Shigella from Salmonella?

A

Salmonella: Citrate, H2S and Motility POS

Microbiology (11 decks)

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