Selection of Ampicillin Resistant Bacteria
An ampicillin stock solution can be prepared at a concentration of 100 mg/mL and should be stored at -20⁰C.
Add 1 g (1000 mg) of ampicillin to 10 mL of dH2O Sterilize the solution using a 0.22 μm filterStore solution in different aliquots at -20⁰C LB-ampicillin agar preparation:
Dissolve the following in 500 mL dH2O:
5g tryptone2.5 g yeast extract5.0 g NaCl7.5 g agar25 mg ampicillinOr20 g pre-mixed LB agar powder (or LB agar capsules)25 mg ampicillin. 
Boil solution on stirring hot plate for 1 – 2 min.
Autoclave for 20 minutes and let cool to 50-60⁰C.
Pour approximately 10 mL of molten LB agar into each plate.
Allow plates to solidify for approx.
20 min.
Selection of ampicillin resistant bacteria:
Using a sterile loop, take a sample of suspected ampicillin resistant bacteria from a colony or broth suspension and streak for isolation (using preferred method) on LB-ampicillin plates.
Incubate plates inverted overnight (24 hrs.) at 37⁰C.
Any resulting colonies should represent ampicillin resistant isolates.
