4-2: Columbia CNA with 5% SBA

- Colistin and Nalidixic acid with sheep blood agar

- CNA is selection, SBA is differentiation

state what CNA with SBA means; which part is selection and which is differentiation

the two antibiotics (colistin and nalidixic acid) synergize to inhibit gram- growth (selects for gram+ growth)

what does CNA do

- colistin attacks plasma membrane integrity

- nalidixic acid blocks DNA replication

how does CNA inhibit gram- growth

Staphylococci, Streptococci, Enterococci

state 3 examples of gram+ microbes that grow on CNA/SBA

tests for the presence of hemolysin (a virulence factor)

describe how SBA is used for differentiation

- alpha hemolysis: partial hemolysis (looks green)

- beta hemolysis: complete hemolysis (looks clear)

- gamma-hemolysis: non-hemolytic (no effect)

alpha and beta hemolysis indicate a presence of hemolysin

state and describe the 3 types of hemolysis seen on SBA

- would grow because its gram+

- beta hemolytic because it does complete hemolysis (looks clear)

describe what Streptococcus pyogenes would do on CNA/SBA

- would grow because its gram+

- either alpha or gamme hemolytic because strains can either do partial hemolysis or no hemolysis (look green or have no effect)

describe what Streptococcus gallolyticus would do on CNA/SBA

- would grow because its gram+

- gamma hemolytic because it cannot do hemolysis (no effect)

describe what Staphylococcus epidermidis would do on CNA/SBA

- would not grow because its gram-

describe what E. coli would do on CNA/SBA

1. Staphylococcus epidermidis (alpha hemolysis)

2. Streptococcus gallolyticus (gamma hemolysis)

3. Staphylococcus aureus (beta hemolysis)

4. Streptococcus pyogenes (beta hemolysis)

5. Enterococcus faecalis (gamma hemolysis)

6. Escherichia coli (non-hemolytic)

state what microbe is in each section based on the reaction