1. Blood agar plates (bap)

• Contains mammalian blood, typically at a concentration of 5–10%

• Used to isolate fastidious organisms and detect hemolytic activity (Neisseria and Streptococcus).

2. Chocolate agar (choc)

• blood cells have been lysed by heating the cells to 56 °C

• used for growing fastidious (fussy) respiratory bacteria, such as Haemophilus influenzae.

Remember…

• Various categories of media are not mutually exclusive.

• Ex: blood agar is enriched and differential

• MacConkey agar and MSA are selective and differential

• PEA and CNA are enriched and selective

• Thayer-Martin and Martin-Lewis are highly enriched and highly selective

• Thioglycollate broth (THIO) is a liquid medium that supports the growth of all categories of bacteria.

Examples:

• Hektoen enteric agar (HEA) - selective and differential agar primarily used to recover Salmonella and Shigella from patient specimens

• Salmonella-Shigella agar (SS) – selective and differential for Salmonella and Shigella

• Bile Esculin Agar (BEA) is a selective differential agar used to isolate and identify members of the genus Enterococcus

Fungal Media

1. Sabouraud agar

• Sabouraud agar is used to culture fungi and has a low pH that inhibits the growth of most bacteria; also contains the antibiotic gentamicin to specifically inhibit the growth of Gram-negative bacteria.

2. Hay infusion agar

• Specific for the culturing of slime molds (though not technically fungi).

3. Potato dextrose agar

• PDA is used to culture of certain types of fungi.

Preparation of CM

• Nutrient Broth

• Dissolve 8 g of NB powder in 1000 ml of distilled water in an Erlenmeyer flask. Mix and heat over the magnetic stirrer until the medium becomes clear or transparent.

• Dispense 8 ml of the medium into sterile test tubes.

• Immediately stopper the tubes completely.

• Sterilize in the autoclave at 15 psi, 121 C for 15 mins.

• Nutrient Agar

• Dissolve 28 g of NA powder in 1000 l of distilled water in an Erlenmeyer flask. Mix and heat over the magnetic stirrer until the medium becomes clear or transparent.

• Sterilize in the autoclave at 15 psi, 121 C for 15 mins.

Dispensing the CM

• NA plate

• Lay out several sterile Petri dishes on the table with the cover partially open and dispense the medium inside and inoculating hood.

• Dispense the NA medium (30 ml) and allow 5-10 minutes to elapse before completely covering the dish to avoid contamination.

• When the medium is solidified, label the NA plate. Wrap and label the plate.

• NA slant

• Dispense 8 ml of the medium into sterile test tubes using pipette or syringe.

• Cover the tube partially with sterile cotton plug or screw cap and allow the agar medium to harden in an incline position on an agar slant rack.

• Stopper the tube completely when the medium has solidified. Label the upper portion of the test tube slant.

• Sterilize in the autoclave at 15 psi, 121 C for 15 mins.

• NA deep or butt

• Dispense 8 ml of the medium into sterile test tubes using pipette or syringe.

• Cover the tube partially with sterile cotton plug or screw cap and allow the agar medium to harden in an upright position on a test tube rack.

• Stopper the tube completely when the medium has solidified. Label the upper portion of the test tube slant.

• Sterilize in the autoclave at 15 psi, 121 C for 15 mins.