[In vitro antibacterial activity of fosfomycin]

We have studied the "in vitro" antibacterial activity of phosphonomycin against 93 freshly isolated bacterial strains. Phosphonomycin posses a good activity mainly against Gram positive bacteria. A marked increase in the antibacterial activity "in vitro" is obtained when phosphonomycin is combined with other antibitoics having a similar mechanism of action (i.e. inhibition of cell-wall synthesis). We have also determined the frequency of phosphonomycin-resistant mutants in some of the strains tested for antibacterial activity. High frequency of resistant strains have found in Klebsiella spp.