Viability and ultrastructure of S. aureus treated with fosfomycin

Fosfomycin was administered to logarithmic growing cells of S. aureus ATCC 12600 when the number of viable cells (CFU) was about 5 X 10(7) cells/ml. Within 240 min the CFU i) increased for about 70% when 6 micrograms fosfomycin/ml were administered, ii) decreased for about 91% when 25 micrograms glucose-6-phosphate (G-6-P) were administered in addition to 6 micrograms fosfomycin/ml, and iii) decreased for about 98% when 60 micrograms fosfomycin/ml and 25 micrograms G-6-P/ml were added. By means of turbidity measurements mainly a retardation in cell reproduction could be recognized. Contrary to Gram-negative bacteria, the reduction of viable cells for about 90% was not accompanied by a loss of cell integrity in the same range. In addition to the ATCC strain this could be shown for eight further strains of S. aureus.