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 filter
Store solution in different aliquots at - 20⁰C LB - ampicillin agar preparation :
Dissolve the following in 500 mL dH2O :
5g tryptone ; 2.5 g yeast extract ; 5.0 g NaCl ; 7.5 g agar ; 25 mg ampicillin Or 20 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 .
