Lab 2

Question 1

Brain-heart infusion enrichment

Answer 1

Nutrient-rich medium used to grow a variety of fastidious organisms
- combined boiled bovine or porcine heart and brain with other nutrients

Question 2

5% sheep blood agar plate

Answer 2

A complex, differential media used for isolation and cultivation of pathogenic, fastidious microorganisms

• supports growth of and detects hemolysis by medically important bacteria (yeasts and fungi)
• trypticase soy agar (TSA) used as a base medium to which 5% sheep blood is added once base is cooled to 50 C
• 150 mm plates contain 20 ml of medium

Question 3

MacConkey agar plate

Answer 3

Moderately selective medium for isolation and presumptive identification of enteric bacteria from feces and urine

• useful for isolation and separation of swarming Proteus from other enteric organisms
• used for differentiating certain non-enteric gram neg organisms
• peptones in medium provide nitrogenous nutrients and amino acids
• coliform organisms (lactose fermenters) develop into red/pink colonies surrounded by zone of percipitated bile
• *only certain types of gram neg organisms grow on this agar**

Question 4

Colistin-nalidixic acid (CNA) blood agar plate

Answer 4

Blood agar to which antibiotics (colistin and nalidixic acid) have been added to preclude growth of gram neg organisms

• colistin = peptide antibiotic
• nalidixic acid = quinolone antibiotic
• both have gram neg activity*
• *only gram positive organisms will grow on CNA**

Question 5

Complex media

Answer 5

Can not be chemically defined

• usually contain a type of biological fluid or component
• ex: blood, serum, bile salts

Question 6

Chemically defined media

Answer 6

Every component is chemically known and added at a defined concentration

Question 7

Differential media

Answer 7

Has some type of indicator or indicator system added to it

- ex: blood for hemolysis detection or specific carbs, or dye to indicate fermenation

Question 8

Selective media

Answer 8

Have some type of inhibitor added to prevent the growth of certain organisms
- ex: antibiotics, high salt concentrations, growth inhibiting dyes (crystal violet)

Question 9

What media does CNA replace?

Answer 9

Phenyl ethyl alcohol (PEA)
- had tendency to rapidly evaporate during cold storage, in the set of general media for inoculation of medical microbiological specimens

Question 10

Non lactose fermenters in MacConkey

Answer 10

Develop into colorless, transparent colonies

- salmonella, shigella

Question 11

____ and _____ inhibit gram pos and many gram neg bacteria

Answer 11

Bile salts and crystal violet