In vitro potentiation of cephalosporins by alafosfalin against urinary tract bacteria.

Potentiating activity of alafosfalin was examined in detail with 8 cephalosporins and mecillinam against 164 urinary bacteria representing 8 genera. Alafosfalin was generally comparable in activity to cefamandole and mecillinam but superior to other cephalosporins tested. When the minimal fractional inhibitory concentration indices were compared, synergism was observed with all of the beta-lactams tested for all species except Streptococcus faecalis. Marked synergism was observed with Escherichia coli, Citrobacter, and enterobacter and, among the drugs tested, with cefamandole and mecillinam. Although alafosfalin is inactive against Pseudomonas aeruginosa, potentiation was seen with cefsulodin. The most favorable combination ratio of alafosfalin/cephalosporin to elicit potentiation was determined for each species and occurred in a rather narrow range of combinations (1:4 to 4:1 in general).