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Liz's Microbiology Module 1 > Enterobacteriaceae > Flashcards

Enterobacteriaceae Flashcards

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1
Q

Sites where members of the Enterobacteriaceae are considered “usual flora”

A

GI tract, uncommon normal flora of other areas

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2
Q

Sites where members of the Enterobacteriaceae are always considered pathogenic

A

Normally sterile areas

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3
Q

Characterisitics that are common among all members of Enterobacteriaceae

A
  1. GNR (straight)
  2. Facultative anaerobes
  3. Peritrichous flagella (if motile)
  4. Ferment glucose
  5. Nitrates reduced to nitrites
  6. Oxidase negative
  7. Grows well on MAC agar
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4
Q

What do Enterobacteriaceae generally look like on a SBA?

A

Large, smooth, gray colonies on SBA

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5
Q

Factors which contribute to pathogenicity of Enterobacteriaceae

A
  1. Endotoxins
  2. Exotoxins
  3. Invasiveness
  4. Adherence to epithelial cells
  5. Capsules
  6. Colonization
  7. Certain Ags
  8. Hemolysins/enzymes
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6
Q

When trying to isolate from areas w/ normal flora, you may need to…

A

Add several types of differential and selective media

- Stool → MAC, HEK, XLD for example

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7
Q

5 identification schemes of identifying Enterobacteriaceae

A
  1. Crosshatch/checkerboard
  2. Grouping systems
  3. Branching flow diagrams
  4. Numerical coding systems
  5. ?
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8
Q

Problem w/ crosshatch/checkerboard methods

A

Accurate but tedious

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9
Q

Problem w/ grouping system s(Edwards and Ewing)

A

Quicker but additional material may be needed

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10
Q

Problem w/ branching flow diagrams

A

Simple but dangerous

- Atypical organisms may be misidentified

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11
Q

Problem w/ numerical coding systems

A

Need to use your brain and not rely strictly on the number identification

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12
Q

Purpose of serologic typing

A
  • Identification of isolate

- Epidemiologic “fingerprinting” (helps trace where it’s coming from)

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13
Q

Most frequently serotyped GNRs

A
  • Salmonella
  • Shigella
  • Escherichia coli (selective isolates)
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14
Q

Serologic typing antigenic structure

- K (name and 3 facts)

A

Capsular Ag

  • Polysaccharide
  • Heat labile
  • May block O Ag
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15
Q

Serologic typing antigenic structure

- H (name and two facts)

A

Flagellar Ag

  • Protein
  • Heat labile
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16
Q

Serologic typing antigenic structure

- O (name and two facts)

A

Somatic Ag

  • Part of cell wall
  • Heat stable
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17
Q

Serologic typing

  • What media
  • What antisera
  • What to do if O group is blocked
A

Media: non-sugar containing and non-selective media (T. soy, SBA)

  • Antisera: polyvalent
  • If O group is blocked: boil organism and retype (b/c of capsule present)
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18
Q

Problems involved w/ the treatment of infections from Enterobacteriaceae

A
  • High mortality rate for GN septicemia
  • Antimicrobial resistance due to not taking all of antibiotics
  • Potentially harmful effects of antimicrobials used for treatment
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19
Q

Habitat and most common infection involving E. coli

A
  • Large bowel (#1)
  • UTI (#1 most common cause)
  • Gastroenteritis
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20
Q

Habitat and most common infection involving Shigella

A
  • NOT normal flora (#1)/always pathogenic

- Penetrate epithelial cells of intestinal mucosa (blood, mucous, leukocytes)

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21
Q

Habitat and most common infection involving Salmonella

A
  • NOT normal flora (#2)
  • Gastroenteritis (animals)
  • Septicemia (invasive)
22
Q

Habitat and most common infection involving Citrobacter

A
  • GI

- Variety of infections, primarily UTIs

23
Q

Habitat and most common infection involving Serratia

A
  • GI, also respiratory flora
  • Formerly strictly saprophytic now
  • Major nosocomial problem
24
Q

Habitat and most common infection involving Enterobacter

A
  • GI?

- Variety of infections, especially UTIs

25
Q

Habitat and most common infection involving Proteus and Morganella

A
  • GI?
  • UTI…triple phosphate (struvite) crystals
  • Renal stones
26
Q

Habitat and most common infection involving Yersinia

A

Agent of the plague

  • Bubonic (lymph)
  • Pneumonic (lungs)
  • Septicemic (blood)
27
Q

Major source of infection for Enterohemorrhagic E. coli causing gastroenteritis

A

Hamburgers, fruits, vegetables, water (pools), ect.

28
Q

Major source of infection for Salmonella causing gastroenteritis

A

Animals (chickens, turtles, iguanas, etc), food, water

29
Q

Major source of infection for Yersinia pestis

A

Endemic in rodents and transmitted by insect vector, domestic cats to humans

30
Q

Factors contributing to pathogenicity of EPEC and disease caused

A

Enterpathogenic E. coli

  • Due to organism’s ability to adhere to cells in small intestine
  • Infant diarrhea
31
Q

Factors contributing to pathogenicity of ETEC and disease caused

A

Enterotoxigenic E. coli

  • Due to toxins (heat labile toxin and heat stable toxin)
  • Traveler’s diarrhea (Montezuma’s revenge) in developing countries
32
Q

Factors contributing to pathogenicity of EIEC and disease caused

A

Enteroinvasive E. coli

  • Due to ability to invade into mucosal cells of intestine not through blood
  • Similar to Shigella (no specific disease caused)
33
Q

Factors contributing to pathogenicity of STEC, EHEC, VTEC and disease caused

A

Shiga toxin, Enterohemmorrhagic, and Verotoxin E. coli

  • Due to cytotoxins (verotoxins and “shiga-like” toxins)
  • Leading cause of acute renal failure in children
34
Q

Formulate an approach for isolating/identifying E. coli (O157: H7) in stool cultures

  • Media?
  • Biochemical recommendations?
  • Typing recommendations?
A

???

  • Use sorbitol MAC (will be sorbitol neg)
  • Run a MUG test (will be m
35
Q

Applications and advantages of shiga toxin testing on stool samples

A
  • Some sorbitol positive STEC strains identified (would be missed by culture)
  • Assay will detect serotypes other than O157
36
Q

Compare and contrast the pathogenic mechanism involved in E. coli, Shigella, and Salmonellas gastroenteritis

A

???

37
Q

Typhoid Fever

  • Recommended type of specimen
  • Characteristics of the disease
  • Specific characteristics for identification of pathogen
A
  • Test positive in blood cultures
  • Man only host, invasive, high fever, carriers harbor in gallbladder
  • Serotyping required for identification: it’s positive w/ Vi and group D antisera (may have to boil to get rxn w/ group D antisera)
38
Q

Most common enteric agent of infection

- Urinary tract

A

E. coli

39
Q

Most common enteric agent of infection

- Abdominal wound

A

??

40
Q

Most common enteric agent of infection

- Newborn meningitis

A

??

41
Q

Msot common enteric agent of infection

- Gastroenteritis

A

Salmonella

42
Q

Most commen enteric agent of infection

- HUS

A

Enterohemorrhagic E. coli (STEC, EHEC, VTEC)

43
Q

Most common enteric agent of infection

- Pneumonia

A

Klebsiella pneumoniae

44
Q

Most common enteric agent of infection

- Typhoid fever

A

Salmonella typhi

45
Q

Most common enteric agent of infection

- Plague

A

Yersinia pestis

46
Q

Name 3 Enterobacteriaceae that are ALWAYS considered pathogens, regardless of specimen site

A

Shigella, Salmonella

47
Q

Habitat and most common infection involving Klebsiella pneumoniae

A
  • Bowel (#2)
  • Pneumonia
  • Nosocomial infections
48
Q

How to differentiate K. pneumoniae vs. K. oxytoca via biochemicals

A
  • K. pneumoniae is indole neg

- K. oxytoca is indole pos

49
Q

How to differentiate P. mirabilis and P. vulgaris via biochemicals

A
  • P, mirabilis is ornithine pos, indole neg

- P. vulgaris is ornithine neg, indole pos

50
Q

How to differentiate E. coli and Shigella via biochemicals

A
  • Shigella is always non-motile, lysine neg, lactose neg
  • E. coli varies
  • Serologic typing required before definitive identification can be made
51
Q

Yersinia enterocolitica

  • Disease
  • How does someone contract it?
A
  • Gastrointestinal (LN of small intestine) → children
  • Contaminated water, food (esp. pork), unpasteurized milk, contact w/ animals
  • Withstand refrigerator temperatures
52
Q

Yersinia enterocolitica

- Stool culture

A

MAC, CIN, YSA at room temperature

Liz's Microbiology Module 1 (11 decks)

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