can anyone suggest why the ampicillin when used as a positive control didnt make a change against bacteria such as pseudo.aerog. and others like listeria? i used it in 48 well plate with broth culture, not agar plate. so i was applying it at RT and there is no hot media or agar that may have degraded the product.
I used 0.2 mg/1ml
do i need to increase the concentration? any reference or guidelines are available and could be helpful on the optimum usage of ampicillin salt??
Always greatly appreciated your help!!