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Microbiology > Lab stuff > Flashcards

Lab stuff Flashcards

1
Q

Three main routes for microbe entry

A

Respiratory

Alimentary/swallowing

Dermal, cuts etc

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2
Q

Colony morphology of Staph aurerus on aerobic blood agar

A

Opaque, white, slightly domes colonies

Circular, 1-2mm diameter

Narrow zone of haemolysis

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3
Q

Which organisms are catalse positive

A

Most gram negative

Useful discriminatory test for gram positive

+ve(fizzing/bubbles)

Staphylococci, Corynebacteria, Bacillus

-ve

Streptococci, Lactobacilli, Clostridium

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4
Q

Target of Oxidase test

A

Detects cytochrome C oxidase

More discriminatory for gram -ve than +ve

Useful for distinuguishing species of Pseudomonas and Vibrio from Enterobacteriaceae

Positive test: Purple within 15 sec

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5
Q

Test for distinguishing Staph aureus from Staph epidermis

A

The coagulase test

Aureus has ability to coagultae plasma,

epidermis doesn’t

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6
Q

For growth microorganisms require:

A
  • A source of energy
  • Carbon, nitrogen, mineral salts and vitamins
  • Certain ‘accessory’ growth factors
  • Water
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7
Q

E. coli appearance on gram stained slides

Cocci/Bacilli

Arrangement

Gram reaction

A

Bacilli

Single cells

Negative

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8
Q

P. aeruginosa appearance on gram stained slides

Cocci/Bacilli

Arrangement

Gram reaction

A

Bacilli

Single cell

Negative

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9
Q

C. perfringens appearance on gram stained slides

Cocci/Bacilli

Arrangement

Gram reaction

A

Bacilli

Single cells

Positive

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10
Q

B. cereus appearance on gram stained slides

Cocci/Bacilli

Arrangement

Gram reaction

A

Bacilli

Single cells

positive

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11
Q

S. Typhimurium appearance on gram stained slides

Cocci/Bacilli

Arrangement

Gram reaction

A

Bacilli

Single cells

Negative

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12
Q

S. Aureus appearance on gram stained slides

Cocci/Bacilli

Arrangement

Gram reaction

A

Cocci

Clusters

Positive

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13
Q

S. pyogens appearance on gram stained slides

Cocci/Bacilli

Arrangement

Gram reaction

A

Cocci

Short chains

Positive

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14
Q

Aerobe/Anaerobe?

E. coli

P. Aeurignosa

C. perfrigens

B. cereus

A

E. coli: Facultive aerobe

P. Aeurignosa: strict aerobe

C. perfrigens: Strict anaerobe

B. cereus: Facultibe aerobe

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15
Q

Use of MacConkeys agar tests…

A

Gut bacteria able to grow in bile salt levels inhibitory to most bacteria. MacConkeys contains sodium taurochloate.

Also conatins lacose and neutral red.

Both a selective and indicator mediuim:

selective: bile tolerance

indicator: lactose utilisign bacteria turn red, others turn it yellow

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16
Q

Expected colours from E. coli and S. Typhimurium on MacConkey

A

E. coli: bright pink colonies

ST: Yellow colonies

As E.coli is able to metabolise the lactose

17
Q

What are the components of COBA

A

Colistin Oxolinic Acid Blood Agar

  • C: Active against gram -ve
  • OA: inhibits gram+ve apart from streptococci

I.E. (B-haemolytic) Selective for streptococci

18
Q

Three types of AB sensitivity testing:

A
19
Q

Define antibiotic syngergism

A

In the synergistic response, the applied antibioticswork together to produce an effect more potent than if eachantibiotic were applied singly

E.G: trimethoprim and sulphamethoxazole bcause the two inhibit two different enzymes in same pathway

20
Q

Define antibiotic antagonism

A

Presence of one AB inhibits action of another

E.G. Nitrofurantoin and nalidixic acid

Bacterocidal(penicillin) ABs can be antagonised by bacterostatic ABs(tetracycline)

21
Q

Timeline in identifying a specimen

A
22
Q

Sabourauds agar is used fro isolation of…

A

Candida albicans

23
Q

Xylose Lysine Sodium Deoxycholate (XLD) and seline broth for isolation of…

A

Salmonaella from faeces

24
Q

Optochin discs used to ID…

A

Strep. pneumonniae

i.e. pneumococci

25
Q

use of bacitracin discs to ID

A

+ve = S. pyogens

26
Q

Sugar fermentation tests for identification of…

A

Enteric gram -ve

27
Q

Positive nagler reaction indicates…

A

Clostridium perfrinigens

28
Q

A positive Elek’s test indicates…

A

Toxin produ tion by Corynebacterium diptheria

29
Q

Define MIC

A

=minimum inhibitory concentration

Lowest concentration at which inhibition is observed

30
Q
A

Microbiology (11 decks)

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