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MEDI2003 Module 2 theory > Miscellaneous Gram Negative Bacteria > Flashcards

Miscellaneous Gram Negative Bacteria Flashcards

1
Q

List two properties/characteristics of Gram Negative endotoxins

A
  • Heat stable
  • Lipid A of GN wall
  • Not antigenic
  • Activates coagulation, complement, fibrinolysis
  • Not secreted - released when cells disrupted
  • Less potent than exotoxins
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2
Q

Which genera from the family of Enterobacteriaceae are always motile?

A

Proteus sp.
Providencia sp.
Morganella morganii

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3
Q

What genera of Enterobacteriaceae would you expect to isolate if an unknown organism was TDA positive?

A

Proteus sp.
Providencia sp.
Morganella morganii

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4
Q

How would you know if unknown organism was a member of the Enterobacteriaceae family and not a member of the Pseudomonas, Vibrio or Aeromonas? (hint: rapid test)

A

Conducting an oxidase test will show rapid distinction between these species because the Enterobacteriaceae family are negative oxidase and pseudomonas, vibrio and Aeromonas are all positive oxidase.

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5
Q

Where is Pseudomonas aeruginosa normally found?

A

In the environment (i.e. soil, plants, water supplies)

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6
Q

Where are O and H antigens located?

A

O antigen is located on the cell wall (lipopolysaccharide) on the organism and H antigen is located on the flagellum.

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7
Q

How could you tell if an organism growing on a culture plate is encapsulated?

A

The growth will have a mucoid texture/look

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8
Q

Where are the members of the genera Haemophilus, Neisseria and Moraxella found as normal flora?

A

Normal flora of the URT

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9
Q

What type of infections are Haemophilus and Moraxella usually associated with?

A

Respiratory Tract infections

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10
Q

Which species of Haemophilus requires both X and V factors but can grow readily on blood agar?

A

Haemophilus haemolyticus

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11
Q

Why are CHOC plates always incubated in CO2?

A

This agar is used to encourage the growth of more fastidious species such as Haemophilus and Neisseria which are both capnophiles therefore they require high a CO2 environment to grow.

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12
Q

Name two pigments produced by Pseudomonas aeruginosa and identify which one is fluorescent under UV light?

A

Green pyocyanin and Yellow pyoverdin (fluorescein)

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13
Q

Compare the infectious dose required for human cholera, salmonellosis and shigellosis. Where are these organisms acquired from? (i.e. what is there usual/natural reservoir?

A

Cholera - Infective dose 10^10 orgs/ml - natural reservoir are contaminated water supplies, fish/shellfish from contaminated water supplies, contaminated foods and asymptomatic carriers.

Salmonellosis - Infective dose >10^5 orgs/ml - natural reservoir are animals such as poultry, cows, pigs, sheep, pets, birds and reptiles.

Shigellosis - Low infectious dose of 10-100 organisms - Associated only with humans.

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14
Q

What would the presence of GNID indicate if seen in a throat swab?

A

Possible Neisseria gonorrhoeae infection

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15
Q

What primary test results would you expect for a member of the Enterobacteriaceae?

A
  • Gram stain - Gram Neg Bacillus
  • non-fastidious
  • Catalase pos
  • Oxidase neg
  • OF - Fermentative
  • Facultative anaerobes
  • All motile genera have peritrichous flagella
  • Grey, moist, shiny looking colonies on BA (slightly more opaque centre than edge)
  • Usually non-haemolytic
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16
Q

How could you rapidly differentiate between the three swarming strains of Proteus sp.? What would be the results for each?

A

Conduct an Indole and Maltose test to differentiate between them.

  • P. vulgaris - Indole pos and Maltose pos
  • P. mirabilis - Indole neg and maltose neg
  • P. penneri - Indole neg and maltose pos
17
Q

List 4 characteristic laboratory features of Pseudomonas aeruginosa.

A 
GNB
Non-fastidious
Obligate aerobe
motile
oxidase pos
OF: oxidative
Distinct colony morphology: flat. matt colonies, uneven periphery, sheild shaped colonies.
18
Q

If you had mucoid LF/LLF growing on CLED or MAC, how could you differentiate this as either an Enterobacter sp. or Klebsiella sp. without setting up overnight tests?

A

check the consistency of the colony. If it’s sticky then it’s most likely Klebsiella.

19
Q

When performing an Indole Spot test what culture plates do we and don’t we take colonies from?

A

Use BA

Don’t use colonies from CLED or MAC

20
Q

What indole reaction will you get from E. coli?

A

Indole pos

21
Q

The family Enterobacteriaceae what are the overt pathogen that we consider significant (hint: they are NOT considered NF)

A
  • Salmonella
  • Shigella
  • Yersinia
  • Diarrhoea producing strains of E. coli.
22
Q

The most common isolates in the clinical lab are from what family of bacteria?

A

Enterobacteriaceae

23
Q

What are the common genera of Enterobacteriaceae? (not the clinically significant overt pathogens)

A
  • Escherichia
  • Citrobacter
  • Klebsiella
  • Proteus
  • Providencia
  • Morganella
  • Serratia
  • Enterobacter
24
Q

What are the non-motile genera of Enterobacteriaceae

A
  • Klebsiella
  • Shigella
  • Yersinia
25
Q

What are the 4 species of Escherichia sp.?

A
  • E. coli
  • E. hermanii
  • E. vulneris
  • E. fergusonii
26
Q

What is the habitat of Escherichia sp.?

A

GIT of humans and animals

27
Q

What is the most common human bacterial pathogen?

A

Escherichia coli

28
Q

What are E. coli’s distinctive features?

A
  • Lactose fermenter
  • Motile
  • Indole pos
  • May be encapsulated (mucoid)
29
Q

How does the Indole test work?

A
  • Tests if an organism produces the enzyme tryptophan

- Tryptophanase breaks down the amino

30
Q

How does the Indole test work?

A
  • Tests if an organism produces the enzyme tryptophan
  • Tryptophanase breaks down the amino acid tryptophan
  • If bacteria being tested is positive for tryptophanase the enzyme will react with kovac’s reagent and turn the API strip pink (ring on surface).
31
Q

List the characteristics of Enterobacter sp.

A
  • Lactose variable (may be mucoid)
  • Motile
  • All are indole neg
32
Q

What are the main species of Enterobacter sp.

A
  • E. cloacea (lactose neg)

- E. aerogenes (lactose pos)

33
Q

What are three distinctive features of Proteus, Providencia and Morganella morganii.

A
  • TDA pos
  • Urea pos
  • Motile (Proteus swarms)
34
Q

What are the four main diseases caused by Salmonellae?

A
  1. Gastroenteritis
  2. Enteric fever (typhoid)
  3. Extra-intestinal infections
    - Carrier status
35
Q

What disease does Shigellae cause? list some symptoms

A 
Bacillary dysentery.
Symptoms include: 
- Inflammatory response
- ulceration
- Bleeding
- Blood, mucous and pus in the stool
36
Q

What are some of the distinctive features of Pseudomonas aeruginosa?

A
  • Pigment production (Green and Yellow)
  • Metallic sheen on BA at 48 hrs
  • Grape-like odour
  • Resistant to many antimicrobials and disinfectants
  • Non-lactose Fermenter on MAC/CLED

MEDI2003 Module 2 theory (5 decks)

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