Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

(MICRO) Cultures and Plates > Media and Plates > Flashcards

Media and Plates Flashcards

1
Q

What are the ‘standard plates’ used for urine specimens?

A

For routine urine culture: MAC (maconkey, for gram negative selection and lactose fermenter identification), CNA (colistin and nalidixic acid),

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the purpose of Bacteroides bile esculin agar?

A

Both inhibitory and differential
Added: bile salts and esculin (differential component)
*kills most bacteria, so it is selective for Bacteroides fragilis group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the purpose of Campy-BAP

A

Inhibitory only
Added: bacitracin, novobiocin, colistin, cephalothin, polymyxin B (these are all narrow spectrum antibiotics)
*most bacteria are inhibited so it is selective for campylobacter jejuni
*NOTE - incubation at 42 degrees celsius is also campy selective

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

CCFA Agar..what is it?

A

*stool culture plate for cdiff
Cycloserine, Cefoxitin (inhibitory componints), Fructose (differential component)
*most bacteria are inhibited so it’s selective for clostridium difficle
*really only c diff grows on it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is CIN mdedia?

A

Cefsulodin, Irgasan and novobiocin (all inhibitory)

*selective media for yersinia spp and Aeromonas spp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is CNA agar?

A

Colistin and nalidixic acid (both inhibitory)

  • selects against gram-negative bacteria only
  • selects FOR gram positive bacteria
  • note, staph aureus is NOT completely inhibited
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is EMB agar?

A

Eosin (inhibitory) with methyliene blue, lactose and sucrose (differential agents)
*selects against gram positives
selects FOR gram negative bacteria
*NOTE lactose or sucrose fermenters are blue-black
*stronger lactose fermenters are green

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is Hektoen enteric agar?

A

Both inhibitory and differential

  • bile salts are inhibitory
  • lactose, sucrose, salicin, bromthymol blue, acid fuchsin are all differential
  • sodium thiosulfate, ferric ammonium citrate are both used for hydrongen sulfide production as a differential component as well
  • selects FOR enteric pathogens and AGAINST gam positives
  • hydrogen sulfide producers turn black, fermenters are green
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is LKV agar?

A

Kanamycin and vancomycin (both inhibitory

  • select against aerobic bacteria and anaerobic gram positives
  • selects for anaerobic gram–negatives
  • pretty much your best Bacteroides spp selective media
  • L is for laked blood, which is nutrient source
  • VRE could be selected for on this medium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is MacConkey agar?

A

MacConkey is a inhibitory and differential agar
*selects against gram positives
*selects for gram negatives and in particlar enteric pathogens
*bioe salsts and crystal violet are inhibitory
Lactose and neutral red are differential
*lactos efermenters are red

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does a Mannitol salt plate do?

A

It is both inhibitory and differential.

  • NaCl high concentrations are inhibitory and select against gram negtives and gram positives other than staph spp
  • best medium for staph aureus in particular
  • coag negative staph grow but do not ferment the mannitol
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is Mycosel agar?

A

AKA Mycobiotic/Mycosel, it is an inhibitory agar that uses chloramphenicol and cycloheximide to select against bacteria and saprophytic fungi
*best for dimorphic fungi and dermatophyte selection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is PC agar?

A
  • note, pseudomonas cepacia is the old/outdated name for burkholderia cepacia
  • Thus, PC would now be ‘BC’ but history prevails so it’s PC for pseudomonas cepacia
  • this inhibitory and differential media uses crystal violet, bile salts for inhibition of gram positives and polymyxin B, ticarcilin for gram negative inhibition and pyrovate for differential
  • select against gram positives and most gram negatives
  • select FOR one particular organism: Burkholderia cepacia
  • pink colonies…pretty specific but not totally for B cepacia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is PEA agar?

A

PEA agar is phenylethyl alcohol agar that selects against gram negatives and FOR gram positives

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the SS plate?

A

Salmonella-Shigella (SS)
uses bile salts and brilliant green for inhibition
uses lactose and neutral red for differential
uses sodium thiosulfate, ferric ammonium citrate for hydrogen sulfide production differentiation
*the goal is inhibit gram positives and select for enteric pathogens
*note, shigella spp may be inhibited

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is sorbitol macocnkey agar?

A

same as macConkey but specific for e coli O157 selection and differentiation as this strain is sorbitol negative (others positive)

17
Q

What is TCBS agar?

A

(ThioCitrateBileSalt) Sodium thiosulfate, sodium citrate, NaCl all select against gram negatives

  • bile salts and NaCl select against gram positives
  • sucrose thymol blue-bromthymol blue are differential all to catch Vibrio spp
  • sucrose fermenters are yellow
  • species that utilize citrate appear blue
18
Q

What is the Martin-Lewis/Modified Thayer Martin agar for?

A

This is GC selective media (Gonorrhea and chlamydia)

  • uses vancomycin for gram positive inhibition
  • uses colistin for gram-negative bacteria inhibition
  • uses trimethoprim for swarming proteus inhibition
  • uses nystatin and amphotericin B for yeast inhibition
  • contains supplements for growth of G and C
  • selects for Neisseria gonorrhoeae and Neisseria meningitidis
  • NOTE use chocolate agar too as some NG strains are inhibited by vanc
19
Q

what is XLD agar?

A

Bile salts, NaCl are for inhibition of gram positives

  • selection FOR enteric pathogens
  • essentially the same purpose as Hektoan enteric agar
  • sodium thiosulfate and ferric ammonium citrate for differential of hydrogen sulfide production
  • lactose, sucrose, xylose and phenol red for differentiation of fermenters
20
Q

When an agar is for ‘enteric pathogens’ what is it looking to select for?

A

Enteric pathogens: Salmonella spp, Shigella spp and Yersinia spp
*note, there are two pages dedicated to new and improved selective and ifferntial media for these bugs in particular in the Koneman’s book…so hold on to the media for enterics a little lightly

21
Q

What is set up for positive blood culture bottles?

A

CHOC, BAP, MAC, CNA, K, SAB

22
Q

What is SAB?

A

Sabouraud Dextrose agar (AKA: SDA plate)

  • used for selection of dermatophytes and fungi, also filamentous bacteria such as nocardia
  • acidity of media is selective against bacteria
  • it contains peptones
  • peptones = in addition to containing small peptides, the resulting material includes fats, metals, salts, vitamins, and many other biological compounds. Peptones are used in nutrient media for growing bacteria and fungi
  • probably not great for yeast, but yeast grow on bacterial plates most often
23
Q

FOR WDL systems, using K plates means what?

A

It’s blood agar for anaerobes. K for CDC anaerobic plates. don’t know why

24
Q

If you see yeast growing, what are the first steps towards identification of those yeast species?

A

GT and RAT (from WDL policy)

  • GT = germ tube test; RAT = Rapid Assimilation Trehalose Broth
  • RAT test is for candida glabrata (if morphology rules out glabrata, can omit the rat test)
25
Q

What is PD agar? Why would WDL policy have this agar on the list of those to use for identification of yeast with bacterial overgrowth? Why would they have it listed as PD/TA?

A

AKA = PDA –> potato dextrose agar

  • Potato Dextrose Agar (PDA) is used for the cultivation of fungi. Potato Dextrose Agar (PDA) is a general purpose medium for yeasts and molds that can be supplemented with acid or antibiotics to inhibit bacterial growth. The nutritionally rich base (potato infusion) encourages mold sporulation and pigment production in some dermatophytes.
  • Potato Dextrose Agar is composed of dehydrated Potato Infusion and Dextrose that encourage luxuriant fungal growth. Agar is added as the solidifying agent. Many standard procedures use a specified amount of sterile tartaric acid (10%) to lower the pH of this medium to 3.5 +/- 0.1, inhibiting bacterial growth. Chloramphenicol acts as a selective agent to inhibit bacterial overgrowth of competing microorganisms from mixed specimens, while permitting the selective isolation of fungi.
  • Thus, a PD/TA plate is potato dextrose to grow the yeast and TA or tartaric acid to lower the pH to select AGAINST bacteria and FOR the yeast
26
Q

What are the principles of the GT test?

A

For yeast identification, GT and RAT tests are used
GT= Germ tube
*Germ Tube Test is a screening test which is used to differentiate Candida albicans from other yeast. Germ tube (GT) formation was first reported by Reynolds and Braude in 1956. When Candida is grown in human or sheep serum at 37°C for 3 hours, they forms a germ tubes, which can be detected with a wet KOH films as filamentous outgrowth extending from yeast cells. It is positive for Candida albicans and Candida dubliniensis. *NOTE ON SENSITIVITY Approximately 95 – 97% of Candida albicans isolated develop germ tubes when incubated in a proteinaceous media.
*making germ tubes = candida

27
Q

What are the principles of the RAT test?

A

For yeast identification, GT and RAT tests are used

  • RAT = rapid trehelose assimilation
  • PROCEDURE = take plated isolates (colony) –> Inoculate the Rapid Trehalose Broth (commercial product) with the yeast isolate, creating a suspension at least as dense as a 1.0 McFarland Standard –> Incubate the test at 42ºC. for three hours –> Observe for a color change from blue to yellow. Do not read the tubes after three hours.
  • NOTE - the temperature adds to specificity of reaction. Glabrata is the species of candida that ‘assimilates’ the molecule trehelose
  • color change = glabrata
28
Q

During rapid preliminary identification of yeast strains, how do you interpret GT and RAT tests?

A
  • Germ Tube positive, Rat negative > C. albicans/dublinesis - Refer to MALDI-ToF for definitive identification.
  • Germ Tube negative, Rat positive, small yeast on microscopic exam > C. glabrata
29
Q

If the GT and RAT tests don’t give you a candida species, what other test is used at WDL?

A

Vitek 2 YST test

  • interpretation ‘breakpoint’ is 90%. IF 90% or greater you confirm the macroscopic and CM morphology and report
  • if less than 90%, check morphology again and bring it up at rounds
30
Q

What is the Vitek 2 YST test and how does it work?

A
  • self contained commercial testing platform and instrument pair from bio-merieux that allows for many different species of yeast to be identified
  • uses proprietary fluorescent-based probes and several biochemical assays to come to an answer
31
Q

In what clinical scenario do we at WDL use the GT/RAT test for candida?

A

Pretty much exclusively urines. We will report candida albicans/dublinensis in those scenarios
*NOTE on deeper infections identifying to species level is a must, as that drives antimicrobial choices

32
Q

What, in general, are the best therapy choices for candida species?

A

Echinocandins are the best bet susceptibility-wise, but they don’t get into urines well. With GLABRATA, there is high likliehood of echinocandin resistance. Glabrata is also more likely to be fluconazole resistant (10% or so by one paper)
*tropicalis and parapsilosis have low but ‘there’ resistance to fluc

(MICRO) Cultures and Plates (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions