In vitro investigations with fosfomycin on Mueller-Hinton agar with and without glucose-6-phosphate.

Determination of the minimal inhibitory concentration of fosfomycin in the agar dilution test on Mueller-Hinton agar showed that the addition of glucose-6-phosphate to the nutrient medium potentiates the action of fosfomycin against Escherichia coli, Klebsiella, Enterobacter, Citrobacter and Staphylococcus aureus, sometimes by as much as 256-fold. Such a potentiation of action was not detectable with Serratia marcescens, the individual Proteus species, Pseudomonas aeruginosa or enterococci. Fosfomycin is very effective against most medically important bacterial species on Mueller-Hinton agar containing 25 micrograms/ml glucose-6-phosphate. Over 90% of the cultures of E. coli, Citrobacter, Enterobacter, S. marcescens,Proteus mirabilis, Proteus vulgaris, Proteus rettgeri, P. aeruginosa, S. aureus and enterococci examined were inhibited by less than or equal to 64 micrograms/ml fosfomycin.