Selective and Differential Media

EMBSelective for Gram negative

E.coli has green metallic sheen

No growth of Gram pos Staph aureus

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.

MSA with Staph aureus

Mitis Salivarius Agar

Mitis Salivarius

Agar

Mitis Salivarius Agar

BLOOD AGAR: Enrichment media, and Differential

Fish Eye Colonies of

Enterobacter on blood agar

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.

Antibiotic Sensitivity

Antibiotic Sensitivity

Organism is resistant to the antibiotic

Organism is susceptible to the antibiotic

To make 5 quadrants, draw a Y and then add 2 more lines like a mustache.

Antibiotic Sensitivity: Check zone diameters on given table

Organism is resistant to the antibiotic

Organism is susceptible to the antibiotic

Organism has intermediate resistance to the antibiotic

Coagulase Test:Differentiates S. Aureus from S epidermidis

Positive:S. aureus

Negative:S. epidermidis