Microbiology: Common Media

Blood Agar: Components

• Tripticase soy agar, blood (sheep/beef heart)

• hemin (factor X), but no free NAD (factor V)

  • Note: different from chocolate agar which contains factor V

Blood Agar: Purpose

• Enrichment

  • Differential: hemolysis (alpha, beta, gamma)

Bordet-Gengou: Components

Potato, defibrinated blood, methicillin

Bordet-Gengou: Purpose

Selects for Bordetella pertussis (bacteria that causes whooping cough)

How does Bordet Gengou agar select for Bordetella pertussis?

Potato Infusion/Starch: Provides essential nutrients and absorbs toxic fatty acids found in respiratory secretions or swab fibers that can stop unwanted bacterial growth + selective antibiotics (normal throat and nasal flora).

Buffered Charcoal Yeast Extract (BCYE): Components

yeast, agar, charcoal, salts w/ antibiotics = selective

What type of media is buffered charcoal yeast extract (BYCE)? (e.g., enriched, differential, selective)

Selective

Buffered Charcoal Yeast Extract (BYCE) selects for..

Legionella spp.

Campy-blood: Components

numerous antibiotics, Brucella agar base, sheep blood

Campy-blood: purpose/ selects for..

Campylobact spp.

Cefsulodin-irgasan-novobiocin (CIN): Components

peptone base, yeast, mannitol, bile salts, antibiotics, neutral red+crystal violet indicators

Cefsulodin-irgasan-novobiocin (CIN) purpose/ selects for…

Yersinia spp. (may be useful for Aeromonas)

Chocolate Agar: Components

peptone base, hemin, hemoglobin or IsoVitaleX

• Lysed RBCs release factor X and V

Chocolate Agar purpose/ selects for..

Neisseria, Haemophilus

Chormagar MRSA: Components

Cefoxitin

Chromagar MRSA purpose/ selects for..

• Selective: for cefoxitin resistant species

  • Differential: mauve colonies = MRSA+

What colonies on a Chromagar MRSA plate would indicate MRSA+?

Mauve colonies

Chromagar (Spectra) VRE: Components

Phosphatase, alpha-galactosidase, Vancomycin and additional antibiotics

Chromagar (Spectra) VRE purpose

• Selective: Vancomycin resistant species

  • Differential:

    • Navy colonies: (VR - vancomycin resistant) E. faecium

    • Blue/ light blue: (VR) E. faecalis

Chromagar (Spectra) VRE is a selective media that selects for Vancomycin resistant species. It is also a differential media for the bacterium that do grow on it. You notice two visibly different colonies - navy and light blue. The navy colonies are most likely…

(VR) E. faecium

Chromagar (Spectra) VRE is a selective media that selects for Vancomycin resistant species. It is also a differential media for the bacterium that do grow on it. You notice two visibly different colonies - navy and light blue. The light blue colonies are most likely…

(VR) E. faecalis

Chromagar Orientation: Components

Peptone, yeast extract

Chromagar Orientation is mostly used to test what specimen type?

Urine specimenC

Chromagar Orientation purpose

A differential media that results in a range of colors corresponding to common urinary pathogensY

You notice pink colonies on a chromagar orientation. What species of bacteria could these colonies belong to?

E. coliC

Columbia CNA Agar: Components

sheep blood, colistin and nalidixic acid

Columbia CNA Agar purpose/ selects for…

Gram positive bacteria (inhibits Gram negatives)

Cystine Heart Agar (Cystine Glucose Blood Agar): Components

cystine, dextrose/ glucose, blood

Cystine Heart Agar (Cystine Glucose Blood Agar) purpose/ selects for..

Francisella tularensis