Cloning and molecular epidemiology of plasmid-determined fosfomycin resistance.

The plasmid determinant of resistance to fosfomycin (For) was cloned into pBR322 and located in a 0.7-kilobase segment of DNA by transposon mutagenesis and in vitro deletion analysis. It encodes an 18-kilodalton protein located in the cytoplasm of resistant cells. Its synthesis is constitutive. The For genetic determinant is common to all plasmids isolated since 1975 in an hospital environment as determined by DNA-DNA hybridization. However, plasmids which carry For can be divided into two groups on the basis of size, pattern of antibiotic resistances, incompatibility specificity, and restriction and hybridization properties.