1. Selective and Differential Media

2. EMB Selective for Gram negative E.coli has green metallic sheen
No growth of Gram pos Staph aureus

3. MSA: Selective and Differential
Selective because of salt: only Staph can grow
Differential because S. aureus ferments mannitol sugar (turns it yellow) but Staph epidermidis does not ferment mannitol. Note there is no growth or fermentation from M. luteus.

4. MSA with Staph aureus

5. Mitis Salivarius Agar

6. Mitis Salivarius Agar

7. Mitis Salivarius Agar

8. BLOOD AGAR: Enrichment media, and Differential

9. Fish Eye Colonies of Enterobacter on blood agar

10. MacConkey’s Agar: Selective and Differential
Selective because Gram pos are inhibited by the bile salts. Differential because it has lactose. Gram negs that ferment lactose turn yellow.

11. Antibiotic Sensitivity

12. Antibiotic Sensitivity
Organism is resistant to the antibiotic
Organism is susceptible to the antibiotic

13. Antibiotic Sensitivity: Check zone diameters on given table
Organism has intermediate resistance to the antibiotic
Organism is resistant to the antibiotic
Organism is susceptible to the antibiotic

14. Coagulase Test: Differentiates S. Aureus from S epidermidis
Positive:
S. aureus
Negative:
S. epidermidis