ampicillin analog?

[Alexander N. Kukushkin]

>   We're using an ampicillin based expression system but may be having
>   trouble with scale-up due to ampicillin depletion. My boss remembers
>   seeing an lactamase resistant analog of ampicillin compatable with
>   our AmpR vector. Can anyone provide a refference to such an
>   antibiotic?
>
Probably this is a carbenicillin that is produced by Sigma in particular
(Cat. N C1389).
Alex