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1
Q

what is the role of the veterinary technician in microbiology

A

Isolate the pathogen, identify the pathogen, determine which antibiotics will effectively kill the pathogen, report finding to the veterinarian/ clinic.

2
Q

what is the sequence of tests for microbial specimens

A
  1. collect sample
  2. gram stain (microscopic exam)
  3. inoculate culture media
  4. incubate 18 - 24 hours at 37 degrees celsius
3
Q

What are the 5 types of bacteriological media we can use

A

agar, broth, plate, tube, slant

4
Q

what are the 6 types of culture media

A

transport, nutritive, selective, differential, enriched, enrichment

5
Q

what is transport culture media?

A

keeps microorganisms alive; no growth

6
Q

what is nutritive (general purpose) culture media?

A

growth of all types of bacteria and some fungi e.g. chocolate agar, blood agar

7
Q

what is selective culture media?

A

contain compounds that inhibit growth of certain types

organisms; selects for certain bacteria

8
Q

what is differential culture media?

A

differentiates between certain types of bacteria based on biochemical reactions e.g. lactose fermenters

9
Q

what is enriched culture media?

A

addition of blood, serum or egg

10
Q

what is enrichment culture media?

A

liquid media favours growth of certain bacteria

11
Q

what must all media be checked for?

A

accidental contamination

12
Q

what are some gram-positive culture media plates?

A

Columbia collistin-naladixic acid agar (CNA); Phenylethyl alcohol agar (PEA)

13
Q

what are some gram-negative culture media plates?

A

MacConkey (MAC), Eosin methylene blue (EMB), Salmonella-Shigella agar (SS) and Bismuth Sulfite agar

14
Q

What is important about Blood agar plates or trypticase

soy agar?

A

5% sheeps blood

-differential )allows hemolytic reaction to be seen)

15
Q

What is alpha hemolysis?

A

incomplete hemolysis; narrow greenish or slimy band around bacterial colony

16
Q

What is beta hemolysis?

A

complete hemolysis; no change in appearance of agar around colony

17
Q

what is delta hemolysis?

A

double zone of hemolysis

18
Q

what is uricult?

A

a combination/modular media

good for urine

19
Q

what structure allows bacteria to be motile?

A

flagellum

20
Q

what are motility test medium used for?

A

used to show bacterial motility
motility: growth throughout medium
no motility: growth along stab line only

21
Q

what are 9 tests used for identification of bacteria?

A

gram stain, acid fast stain, potassium hydroxide, catalase, coagulase, kirby-bauer sensitivity, optonchin susceptibility, oxidase, CAMP

22
Q

If you don’t have a gram stain what test can u use?

A

KOH test

23
Q

what is the KOH test? how does it work?

A

it is a general test for differentiation of Gram + and Gram - bacteria
- 3% KOH added to a colony on a glass slide, mix for 2 min, if you get a mucoid appearance and a sticky strand = gram postitive, if no change = gram negative

24
Q

what is the catalase test? how does it work?

A
  • finds gram+ cocci and small gram + rods
  • wooden applicator stick used to smear small amount of colony to be tested onto slide, a drop of 3% hydrogen peroxide
  • bubbling = postive reaction
25
Q

what genus are positive on the catalase test?

A

Staphylococcus spp.

26
Q

what genus are negative on the catalase test?

A

Streptococcus spp.

27
Q

What test can be also used for Staphylococcus spp.

A

Coagulase test

28
Q

how does the coagulase test work?

A

a sample of Staphylococcus colony placed in small amount of rabbit plasma with EDTA, incubate overnight

  • if plasma gels= coagulase - positive Staphylococcus spp = S. aureus
  • if plasma remains liquid = coagulase-negative = S.epidermidis
29
Q

what is the lancefield grouping based on?

A

antigenic difference in cell wall carbohydrates

30
Q

what is the lancefield grouping used for?

A

used for group catalase-negative and coagulase-negative bacteria

31
Q

what are the ten tubes of broth and agar

A

trpyricase soy broth, brain-heart infusion, thioglycollate broth, gram-negative broth, urea agar slant, bile esculin again, simmon’s citrate tubes, triple sugar iron agar, sodium chloride 0.85%, motility test medium

32
Q

what is trypticase soy broth used for?

A

general use, grows most bacteria (fastidious bacteria especially), blood culture, sterility testing

33
Q

what is brain heart infusion used for?

A

-enriched broth: used to bring bacteria to certain turbidity level for diffusion antibiotic sensitivity testing

34
Q

what is the brain heart infusion agar used for?

A

used to determine oxygen requirements of bacteria

35
Q

what is the thioglycollate broth used for?

A

grows most bacteria, anaerobic bacteria and some fungi, blood culture, can also be used to determine oxygen requirements for bacteria

36
Q

what are gram-negative broth used for?

A

used in fecal culturing-enrichment medium for growing Samonella spp. and Shigella spp.

37
Q

What is urea broth agar slant used for?

A

determines whether bacteria produce urease

-the ammonia reacts with the pH indicator phenol red, turing the broth a hot pink color

38
Q

what does urease degrade into?

A

it degrades urea into ammonia, water, and CO2

39
Q

What are Bile esculin agar tubes used for?

A

primarily used to differentiate Streptococcus spp from Enterococcus spp.
A positive reaction = ferric citrate in agar turns dark brown to black
-bile salts are selective (Gram + inhibited)

40
Q

What are simmons citrate tubes (slant) used for?

A

differentiates bacteria according to their use of citrate

  • often used to differentiate Gram negative bacteria
  • postive result - deep blue color
  • unchanged medium = green
41
Q

what does the sodium chloride 0.85% test do?

A

-sterile solution used for diluting Gram negative bacteria for API20E

42
Q

What does triple sugar iron agar do?

A

classifies bacteria based on ability to ferment glucose, lactose and sucrose

43
Q

what does yellow mean in triple sugar iron agar?

A

fermentation of carbohydrates produces acid end products and changes phenol red indictor to yellow

44
Q

what is the ph indicator color for triple sugar iron agar?

A

phenol red

45
Q

what also can triple sugar iron agar classify?

A

bacteria based on hydrogen sulfide production (blackening) and gas production (bubbles and cracks)

46
Q

What are some musts of Antibiotic discs?

A
  • must be kept at 4 degrees C
  • must not be expired
  • must be monitored using controlled organisms
  • drug concentration = therapeutic levels in animals
  • must be 10 to 15 mm from the plate edge
47
Q

what is direct sensitivity testing?

A
  • application of undiluted samples (urine)

- precision increased when only 1 organism present

48
Q

For indirect sensitivity testing what degrees must it be incubated overnight at?

A

37 degrees C

49
Q

How often do you read the Kirby-Bauer sensitivity test?

A

18 to 24 hrs

50
Q

What is the Kirby-Bauer sensitivity test?

A

the Mueller-Hinton agar with blood - zones read on top without plate lid
-results can be susceptible,resistant, or intermediate

51
Q

What is the Optochin susceptibility used to detect?

A

Streptococcus pneumoniae

52
Q

Give an example of a bacteria that using an Oxidase test will change to a dark blue colour after 5 minutes?

A

Pseudomonas aeruginosa

53
Q

What is the Mueller-Hinton agar culture media plate used for?

A

general-use medium specifically formulated to give standardized results during antibiotic sensitivity testing (Kirby-Bauer test)

54
Q

For Mueller-Hinton agar culture media plates what can they be enriched with for more fastidious organisms

A

blood

55
Q

What to Salmonella-Shigella agar plates select for?

A

gram-negative bacteria

56
Q

What do Salmonella-Shigella agar plates differentiate?

A
  • colonies on the basis of lactose fermentation (pink)

- differentiate hydrogen sulfide-producing bacteria by the use of ferric citrate in the formula

57
Q

What is a coliform bacteria and example?

A

E.coli

-ferment the lactose = bacterial colonies are always pink

58
Q

What do Salmonella spp produce? ferment lactose?

A

they do not ferment lactose but produce hydrogen sulfide = bacterial colonies are colorless with black centers

59
Q

What do Shigella spp. produce?

A

do not ferment lactose or produce hydrogen sulfide = colorless colonies

60
Q

What do the Bismuth Sulfite Agar culture media plates do?

A
  • supresses growth of coliforms (E.coli)
  • allow growth for Salmonella spp.
  • contains sulfur
61
Q

What does it mean for a media to be modular/combination

A
  • chambered agar plates with a variety of selective and non-selective agar
  • enterotubes with a variety of media for enteric bacteria
62
Q

Describe the Mannitol Salt Agar? use? about it? is it used often?

A
  • not used routinely
  • 7.5% sodium chloride with selects for halotolerant organisms (Staphylococcus spp.)
  • Mannitol and phenol red (pH indicator) differentiate between organiusms which can ferment mannitol and those that cannot
63
Q

What does the PEA agar stand for and what does it select for?

A

Phenylethyl alcohol agar, selection = gram postitive

64
Q

What does CNA agar stand for? and what does it select for?

A

Columbia colistin-nalidixic acid with 5% sheeps blood

-select for gram positive organisms

65
Q

Describe the Eosin Methylene Blue culture media plate?

A

-selects for gram negative bacteria
-differentiates between lactose and non-lactose fermentators
-strong acid production = metallic green (E.coli)
-weaker fermentation of lactose = pinkish purple
non lactose = colorless

66
Q

what does the MacConkey ll agar plate select, and what does it use for it? What inhibits the growth of gram positive bacteria.

A
  • the bile salts select for lactose-fermenting
  • crystal violet inhibits growth of gram-positive
    indicators: lactose and phenol red