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Clinical Microbiology > Enterobacteriaceae Exam 2 > Flashcards

Enterobacteriaceae Exam 2 Flashcards

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Biology 101 flashcards
1
Q

Enterobacteriaceae spp. general characteristics?

A

Gram - bacilli
Non-spore forming
Facultative anaerobes that ferment glucose
Reduces nitrates to nitrites
Oxidase neg
Catalase pos (except for Shigella dysenteriae)

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2
Q

Which organism is the most common cause of nosocomial infections?

A

E. coli (Enterobacteriaceae spp. are the majority of nosocomial infections)

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3
Q

ID for Enterobacteriaceae spp.?

A

Large, gray, smooth colonies on SBAP and chocolate agar.

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4
Q

Which organisms are lactose fermenters?

A

E. coli, Klebsiella pneumoniae, Enterobacter aerogenes, Enterobacter cloacae, and Citrobacter spp.

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5
Q

Which organisms are non-lactose fermenters (lack beta-galactosidase)?

A

Proteus spp., Salmonella spp., Shigella spp., Serratia marcescens, Yersinia enterocolitica.
Shigella does contain beta-galactosidase but not permease so with ONPG is a late lactose fermenter.

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6
Q

What is lactose composed of?

A

Glucose and galactose

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7
Q

What are the 2 enzymes required for lactose to be utilized by bacteria?

A

Lactose permease- Allows for penetration of lactose molecule into bacterial cell.
Beta-galactosidase- Hydrolyzes lactose once within the bacterial cell wall resulting in formation of glucose + galactose.

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8
Q

What are coliforms?

A

Coliform bacteria are non-pathogenic strains of microorganisms (not E. coli 0157:H7).

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9
Q

When are coliforms usually used?

A

As a bacterial indicator of sanitary quality of foods, water, and processing environments.

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10
Q

General characteristics for coliforms?

A

Rod-shaped, gram neg, non-spore forming bacteria which can ferment lactose with the production of acid and gas.

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11
Q

Common coliforms include?

A

Escherichia, Citrobacter, Enterobacter, Klebsiella, and Serratia.

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12
Q

How does disease transmit in Enterobacteriaceae spp.?

A

Endogenous infections-normal flora going into sterile sites
Ingestion of contaminated foods-Shigella and Salmonella
Insect vector- Yersinia pestis transmitted by fleas
Horizontal transmission- person to person; nosocomial infections.

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13
Q

Which organisms are not motile?

A

Klebsiella, Shigella, Yersinia

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14
Q

Which organism creates a swarming effect on blood and chocolate agars?

A

Proteus spp.

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15
Q

If not processed quickly, what media should the specimens should be collected and transported in?

A

Cary-Blair, Amies, or Stuart media

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16
Q

Which media can be used on Enterobacteriaceae spp.?

A

SBAP, Chocolate, MacConkey, HE, XLD, TSI, Salmonella-Shigella agar, Hektoen enteric agar, eosin-methylene blue agar, cefsulodin-irgasan-novobiocin agar, Citrate agar, and phenylalanine agar.

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17
Q

What does ONPG test for?

A

Tests for beta-galactosidase activity and identifies late lactose fermenters (lack permease-color change) from non-fermenters (lack both-no color change).

  • *OPNG is substituted for lactose and enters bacterial cell walls more easily without need for permease.**
  • Shigella sonnei is a late lactose fermenter*
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18
Q

What does TSI contain?

A

Contains glucose, lactose, sucrose, and phenol red as pH indicator; starts red in color.

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19
Q

Why do some slants convert to yellow and back to red in 18-24 hours.

A

Peptones

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20
Q

TSI slant for E. colK i

A

A/A gas +, H2S -

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21
Q

TSI slant for Salmonella

A

K/A gas +, H2S +

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22
Q

TSI slant for Shigella

A

K/A gas -, H2S -

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23
Q

True/false? Most hospital labs will perform gram stains of stool specimens as non-pathogenic intestinal flora look similar to enteric pathogens.

A

False. Will NOT.

If you do a gram stain, look for presence of WBC’s which could indicate invasive pathogen.

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24
Q

Which antigens do Enterobacteriaceae possess?

A

O antigen- somatic (cell wall), heat-stable antigen.
H antigen- flagellar, heat liable antigen
K antigen- capsular, heat-labile antigen

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25
Q

O antigen is used to group which organisms?

A

E. coli, Salmonella, and Shigella

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26
Q

H antigen can be used to group which organisms?

A

Salmonella and E. coli (Shigella non-motile)

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27
Q

K antigen is used to type which organism

A

Klebsiella pneumoniae, K1 antigen of E. coli

28
Q

Presumptive ID for E. coli?

A

Oxidase -, Indole +
Gram neg rods
Growth on MacConkey (pink)
Other characteristics: Simmons citrate negative. Usually motile. Voges-Proskauer test negative.

29
Q

Definitive ID for E. coli?

A

Beta-hemolysis or lactose positive AND PYR negative

30
Q

True/false? E. coli causes both intestinal and extrainestinal pathologies.

A

True

31
Q

What is Enteropathogenic (EPEC)?

A

Primarily in infants and children; outbreaks in hospital nurseries and day care centers; stool has mucous but NOT blood.

32
Q

What is Enterotoxigenic (ETEC)?

A

“Travelers diarrhea” Watery diarrhea without blood self-limiting; travelers are going to underdeveloped countries.

33
Q

What is Enteroinvasive (EIEC)?

A

Produce dysentery-bloody stools, may contain mucus does NOT ferment lactose. Harder to get EIEC than Shigella.

34
Q

What is Enterohemorrhagic (EHEC)?

A

Associated with hemorrhagic diarrhea and hemolytic uremic syndrome (HUS). Does NOT sorbitol. Does NOT contain leukocytes which distinguishes it from dysentery caused by Shigella.

35
Q

What is the treatment for E. coli 0157:H7?

A

Usually fluids, possibly IV, in cases of HUS may need dialysis.

36
Q

How does 0157:H7 differs from other E. coli species?

A

Doesn’t ferment sorbitol creating CLEAR colonies.

37
Q

What is the treatment for ETEC, EIEC, EPEC, EHEC, and EAEC?

A

Rehydration

Antibiotics is contradicted-resistance

38
Q

What is Enteroaggregative (EAEC)?

A

Causes diarrhea by adhering to the mucosal surface of the intestine; watery diarrhea

39
Q

What is the most common cause of UTI’s and kidney infections?

A

UPEC-E. coli

40
Q

What plate should urine specimens incubated to?

A

SBAP and MacConkey

41
Q

What is the significance of finding 3 different colonies on a culture plate?

A

It is considered contaminated and not worked up

42
Q

What are the 2 species for Salmonella?

A

S. enterica (human pathogen) and S. bongori (animal pathogen)

43
Q

What are the 3 important serotypes of S. enterica?

A

Typhimurium, Enteritidis, and Typhi

44
Q

What species has been tied to contaminated milk?

A

Salmonella serotype Typhimurium

45
Q

What is salmonellosis?

A

Accumulation of Salmonella bacteria causing gastroenteritis aka food poisoning.
Most cases resolved without antibiotics.

46
Q

Which Salmonella serotype is the most common in the US?

A

Enteritidis

47
Q

Which Salmonella serotype only lives in humans but is not normal flora? What disease does it cause?

A

Salmonella serotype Typhi
Causes Typhoid fever
Spread from person to person

48
Q

Who would be the primary reservoir for Shigella?

A

Humans; flies may spread bacterium from feces to food as well.

49
Q

General characteristics of Shigella?

A

Grows well on MacConkey’s, HE, XLD
Non-lactose fermenter, non-motile
Methyl red +, VP -, citrate -

50
Q

Why would you need to boil Shigella spp.?

A

Boiling removes the capsule. Boiling kills the organism but doesn’t alter the antigen.

51
Q

General characteristics for Klebsiella, Enterobacter, Serratia, and Hafnia spp.?

A

Some are non-motile

Citrate + H2S - VP + Urease + Phenylalanine deaminase -

52
Q

What is Klebsiella pneumoniae resistant to? What do the colonies look like?

A

Ampicillin
Large, mucoid, stringy colony
Lactose fermenter, non-motile, encapsulated.
Indole - MR variable VP + Citrate +

53
Q

What organism causes Donovanosis aka granuloma inguinale (STI)?

A

Klebsiella granulomatis

54
Q

ID for Enterobacter spp.?

A

Lactose fermenter
Mucoid colonies
VP +, Indole -, Motile
Often associated with contaminated medical devices

55
Q

ID for Serratia spp.?

A

Motile, DNase and OPNG +
Variable lactose fermenter
Once considered nonpathogenic; now virulent, antibiotics strains exist. Associated with contaminated catheters.

56
Q

ID for Hafnia alvei?

A

Non-lactose fermenter
Citrate -
Has been recovered from stools/wounds

57
Q

ID for Citrobacter spp?

A

Slow lactose fermenter

Opportunistic, nosocomial acquired, UTI, respiratory tract, neonatal meningitis

58
Q

ID for Proteus mirabilis?

A

Swarming growth
Urease + INDOLE -
UTI, wound infection, pneumonia, septicemic
Antibiotic SUSCEPTIBLE

59
Q

ID for Proteus vulgaris?

A

Swarming growth
Urease + INDOLE +
UTI, nosocomial, immunosuppressed
More antibiotic RESISTANT

60
Q

ID for Yersinia spp?

A

Safety pin appearance
Small, pin-point colonies, may or may not produce alpha hemolysis.
Non-lactose fermenting
Bile salts enhance growth

61
Q

ID for Yersinia enterocolitica?

A

Growth on CIN yields bull’s eye colonies (dark red center with surrounding clear halo).

62
Q

What disease is associated with Yersinia pestis?

A

Plaque

63
Q

What BS level should Yersinia pestis be handled?

A

BS level 3

64
Q

Which form of plaque is the most severe?

A

Pneumonic-pulmonary

65
Q

Which organism is associated with cold blooded animals and is uncommon in humans?

A

Edwardsiella tarda

66
Q

ID for Edwardsiella tarda?

A

Non-lactose fermenter

VP - Indole +

Clinical Microbiology (7 decks)

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