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CLS 753 > Micro - Gram Negative Rods (Enterics) > Flashcards

Micro - Gram Negative Rods (Enterics) Flashcards

1
Q

CO2 loving organisms are called ___. Salt loving organisms are called ___

A

Capnophiles

Halophiles

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2
Q

Are Salmonella, Shigella and Yersinia considered normal flora?

A

Salmonella and Shigella are always pathogens

Yersinia sometimes normal flora, sometimes pathogen

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3
Q

Enterics look like this on a gram stain… Enterics have this unique appearance on the gram stain called ___, where the ends are more intensely stained than the middle

A

Short gram-negative rods or coccobacilli

  • plump
  • members indistinguishable

Bipolar staining

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4
Q

All enterics can ferment this sugar… All enterics have this metabolic oxygen requirement for growth…

A

Glucose

Facultative anaerobes

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5
Q

All enterics are catalase ___

A

Positive

-except Shigella dysenteriae

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6
Q

All enterics are oxidase ___

A

Negative

-except Plesiomonas shigelloides

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7
Q

Can enterics form spores? Can enterics reduce nitrate?

A

Never

Yes, into nitrites

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8
Q

Stool cultures routinely screen for these organisms (3)

A

Salmonella

Shigella

Campylobacter

  • most common cause of diarrhea in US
  • in meat
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9
Q

What is the most favored transport medium for stool?

A

Cary-Blair

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10
Q

Stool samples kept on ice must be processed within… Stool samples kept in transport medium must be delivered within…

A

2 hours

4 days

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11
Q

Primary culture media for enterics (4)

A

Blood agar

Chocolate agar

MacConkey agar

Phenylethyl alcohol agar (PEA)

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12
Q

What sugar does MacConkey agar contain? What color is a positive fermentation result?

A

Lactose

Pink colonies with or without pink agar

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13
Q

Motile enterics

A 
Proteus (vulgaris, mirabilis)
Providencia
Morganella morganii
E coli (O157:H7)
Serratia
Salmonella

-mnemonic = PP MESS

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14
Q

To definitively ID E coli, we can add this compound to culture media…

A

MUG = positive

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15
Q

E. coli - clinical findings (3)

A

UTI = most common cause

Septicemia

Nosocomial infections

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16
Q

E. coli - TSI and KIA results

A

TSI = A/A with or without gas

KIA = A/A with or without gas

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17
Q

E. coli - IMViC

A

+ + - -

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18
Q

EHEC is also known as this serotype… The strain produces this cytotoxin called…

A

O157:H7 and O157:nonmotile

Shiga-toxin or Verotoxin

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19
Q

O157:H7 infection can lead to these conditions (2)

A

HUS

Hemorrhagic colitis

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20
Q

O157:H7 - what does the O and H mean?

A

O = cell wall antigen

H = flagella antigen. May/may not be seen (O157:nonmotile)

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21
Q

What 2 tests should be used to differentiate O157:H7 from regular E. coli?

A

Sorbitol-MAC (SMAC)

MUG

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22
Q

O157:H7 - MUG result is…

A

Negative

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23
Q

O157:H7 - what do the colonies look like on a Sorbitol-MAC (SMAC) plate and why?

A

Colorless = does not ferment sorbitol

  • other E. coli strains can = pink
  • confirm non-fermenter with antisera and latex reagents
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24
Q

Klebsiella - what do colonies look like on a MAC plate?

A

Pink colonies = lactose-fermenter

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25
Klebsiella - what special feature about them gives them a mucoid colony appearance?
Capsule
26
Klebsiella - IMViC results
- - + + | - reverse reaction from E. coli
27
Serratia - key feature
Red colonies | -prodigiosin pigment
28
Proteus are highly motile, forming this type of pattern on plates called...
Swarming | -wave-like growth on plates
29
Proteus, Morganella, and Providencia colonies have this color on MAC plates. Why?
Colorless Cannot ferment lactose
30
Proteus TSI and KIA results (2). Why is the slant that color?
Both tubes: K/A with or without gas H2S positive Deaminase reaction (PAD = phenylalanine deaminase) - slant turns yellow, then red again due to deaminase - glucose fermentation only, no lactose fermentation
31
How are Proteus vulgaris and Proteus mirabilis different?
P. vulgaris = indole positive P. mirabilis = indole negative
32
Proteus is similar to this other genus due to TSI and KIA results and H2S production... What test should we use to differentiate Proteus?
Salmonella -both genera are K/A with H2S production PAD (phenylalanine deaminase) -rules out Salmonella/Shigella/Serratia
33
Morganella morganii and Providencia are similar to Proteus, except for these two things
No swarming H2S negative
34
What are the 2 Salmonella species? Salmonella typhi is a serotype of this species
enterica and bongori, but thousands of serotypes enterica
35
S. typhi animal vector?
None - direct human to human transmission - contaminated poultry, dairy products, water
36
Salmonella and Shigella are both very similar. Which genus has more biochemical reactions?
Salmonella - positive for more biochemical reactions than Shigella -Shigella mostly biochemically inert
37
Salmonella vs Shigella - which has the higher infective dose? Which infection can result in a carrier state?
Salmonella = 10^6 cells -Shigella low infective dose (10-200 cells) Salmonella
38
S. typhi - before 3 weeks, we should try to recover the organism from ___ samples. After 3 weeks, collect specimen from ___ samples
Blood Stool - organism hides in gall bladder, sheds in stool - untreated leads to perforated GI tract - high fever that doesn't go away, enlarged lymphs - vaccine available
39
Salmonella possess this structure to allow them to attach to intestinal epithelial cells
Pili | -epithelial cells engulf organism, resist killing
40
Salmonella possess this cell wall structure that is responsible for septic shock and death. S. typhi resist phagocytosis and complement via this structure
LPS O antigen (endotoxin) Capsular Vi antigen - Vi antigen often blocks O antigen - Vi inactivated by boiling 30 mins
41
Salmonella - IMViC reactions
- + - citrate variable
42
Salmonella colonies have this color on MAC plates. Why?
Colorless Does not ferment lactose
43
Enterics that can make H2S
Proteus Salmonella
44
Salmonella has this color on Hektoen Enteric agar and this on XLD
HE = green-black, or green with black center - from sulfur reduction - Salmonella = H2S positive XLD = red with black center
45
Salmonella antisera slide agglutination - can Salmonella be positive for Vi and negative for O? Why or why not?
No O antigen (LPS) must always be present. Vi antigen (capsule) is masking O antigen. Heat suspension to inactivate Vi antigen and retest
46
How many serotypes of Shigella are there? Which one is the most virulent and name the species
4 = serogroups A, B, C, D Shigella dysenteriae = serogroup A
47
Does Shigella have an animal reservoir?
No - only human to human transmission - contaminated food, water - similar to Salmonella
48
What does it mean when an organism requires close contact for transmission?
Organism is sensitive and fragile (ie Shigella)
49
S. dysenteriae produces a cytotoxin called... Which can lead to this condition
Shiga toxin -also produces several enterotoxin HUS - severe infection - similar to O157:H7 infection
50
Shigella colonies have this color on MAC plates. Why?
Colorless Does not ferment lactose
51
Shigella has this color on Hektoen Enteric agar and this on XLD
HE = green XLD = red/colorless
52
How many Yersinia species are pathogenic and what are they? Which one is the bioterror agent?
Y. pestis = bioterror Y. enterocolitica = most common Y. pseudotuberculosis
53
Yersinia pestis causes this disease
Plague (black death) - transmitted by fleas on rats - 3 forms: bubonic, pneumonic, septicemic - endotoxin deposited in capillaries, blocks blood flow = blackening of bodies
54
Yersinia pestis - what is unique about the temperatures it can grow at?
Better growth at room temp than 37C
55
Yersinia pestis has this unique type of bipolar staining that looks like...
Safety pin
56
Yersinia pestis - what do colonies look like at 24 hrs on a blood agar plate? What do colonies look like at 72 hrs?
Pinpoint colonies too small to be seen with the eye -very slow growth White colonies with fried egg appearance
57
Yersinia pestis colonies look like this on a MAC plate...
Colorless = non-lactose fermenter
58
This species of Yersinia mimics appendicitis. Can refrigeration kill it or prevent its growth?
Yersinia enterocolitica No, survives in the cold
59
Yersinia spp selective media is called... What does Yersinia look like on this media?
CIN (Cefsulodin-igrasan-novobiocin) Transparent with red center (bull's eye)
60
This species of Yersinia is a common animal pathogen and rarely causes disease in humans
Yersinia pseudotuberculosis | -seen in people working with animals
61
These 3 enterics are lactose fermenters, the rest are not
Serratia E. coli Klebsiella
62
These 2 enterics can produce capsules
Klebsiella Salmonella typhi
63
Which is the only enteric that is catalase negative?
Shigella dysenteriae
64
No members of Enterobacteriaceae have this type of hemolysis...
Alpha

CLS 753 (12 decks)

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