Loss of penicillin resistance in Paracoccus denitrificans induced by mitomycin C and acridine orange.

In an attempt to eliminate the penicillin resistance gene of P. dentrificans by curing agents, such as acridine orange (AO) and mitomycin C, it was observed that AO treatment caused temporary phenotypic curing where development of sensitivity was a function of concentration of both the curing agent and benzylpenicillin. However, curing with mitomycin produced sensitive clones at a frequency of 6 X 10(-3) and two permanently cured clones were isolated. Heavy metal resistance and resistance to other drugs, however, remain unchanged in the mitomycin-cured isolate.