Gram Negative Rods Flashcards

1
Q

McConkeys agar**

A
  • good for enteric organisms***

- also for nonenterics like Yersinia and Pseudomonas

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2
Q

lactose fermenters vs. nonfermenters**

A

Fermenters

  • turn purple on McConkeys
    1. Fast –> klebsiella, enterobacter, E. coli
    2. slow –> citrobacter, serratia

Non-fermenters

  • turn clear on McConkeys
    1. oxidase + –> pseudomonas*
    2. oxidase - –> salmonella, proteus, shigella, yersinia
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3
Q

gram negative rods

A
  • thin peptidoglycan wall surrounded by LPS –> Lipid A endotoxin
  • enterobacteriacea family
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4
Q

Klebsiella pneumoniae

A

-pneumonia in alcoholics and diabetics*

  • red “jelly” sputum in lungs
  • HEMORRHAGIC lungs***
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5
Q

E. coli

A
  • fibrimbiae attach to mucosa and can climb mucociliary tract
  • most don’t have a capsule
  • capsule (K antigen) seen in meningeal strains*** (ex. meningitis in newborns)
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6
Q

types of E. coli***

A
  1. enterohemorrhagic (EHEC) –> hemorrhagic/bloody diarrhea
  2. enterinvasive (EIEC) –> shigella like dysentery
  3. enteropathogenic (EPEC) –> childrens diarrhea
  4. enterotoxigenic (ETEC) –> travelers diarrhea (clear)
    - due to inc cAMP/GMP –> inc water secretion
  • EHEC and EIEC more invasive –> bloody diarrhea***
  • EPEC and ETEC less invasive –> clear diarrhea***
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7
Q

EHEC

A

-E. coli 0157:H7**

  • only the toxin causes the illness***
  • no invasion of host

-HUS in children***** (hemolytic anemia, thrombocytopenia, renal failure)

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8
Q

EIEC

A

-only the organism kills it with invasion, not the toxin***

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9
Q

enterobacter

A
  • nosocomial UTIs

- resistant to antibiotics

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10
Q

citrobacter and serratia

A

citrobacter
-normal gut flora

serratia**

  • red colonies (red pigment)**
  • nosocomial
  • cause osteomyelittis in IV drug users
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11
Q

MacConkey lactose fermenters***

A
  1. citrobacter (slow)
  2. serratia (slow)
  3. klebsiella (rapid)
  4. enterobacter (rapid)
  5. E. coli (rapid)
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12
Q

Pseudomonas aeruginosa

A

-resistant attitude –> use antipseudomonal drugs

  • BE PSEUDO**
  • external otitis “swimmers eare”**

-loves water*

  • blue-green pigment (pyocyanin)
  • flourescent green colonies on culture**
  • grape-like odor**
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13
Q

salmonella

A
  • flagellated (motile)
  • spread bloodstream
  • 2 types: typhoid fever and diarrhea
  • bloody diarrhea + fecal leukocyte (monocytic response)
  • osteomyelitis in sickle cell patients***
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14
Q

salmonella typhi (typhoid fever)

A

-fever, constipation, diarrhea

  • Rose spots** (macules on trunk/abdomen)
  • Pulse-temp dissociation** (high fever, slow pulse)
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15
Q

Shigella

A
  • no flagella (non-motile)
  • spread cell to cell
  • invades mucosal cells (Peyer’s patch M cells) inducing apoptosis
  • very few bacteria can cause disease*
  • PMN (neutrophil) response
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16
Q

Proteus

A
  • swarming phenotype** –> bulls eye on blood agar
  • no individual colonies**

-produces urease** –> alkaline pH with ammonia (protects stomach) –> massive kidney stone (staghorn) from high pH**

17
Q

Helicobacter Pylori

A
  • primary cause of gastritis and peptic ulcers**
  • urease +
  • urea breath test POS*** - diagnostic
18
Q

Legionella

A
  • flu like pneumonia (rapid progression to severe)
  • silver stain (hard to gram stain)
  • require special cultures –> Buffered charcoal yeast extract (BCYE)**
  • cough/diarrhea/confusion*(low Na)/G. stain neg.
19
Q

Bacteroides fragilis

A
  • obligate anaerobe (GNR) - can’t breath air

- part of polymicrobial GI infections