Combination effects of cephalexin and gentamicin on Edwardsiella tarda and Streptococcus iniae.

The objective of this study was to determine the in vitro activity of cephalexin-gentamicin combination by a microbroth chequerboard technique against clinical isolates of Edwardsiella tarda and Streptococcus iniae. Gentamicin was shown more susceptible than cephalexin against both bacteria. The effect of cephalexin-gentamicin combination against both bacteria represented additive interaction. The combination even showed synergic interaction (22%) against E. tarda, with a FIC index of <0.5 as a borderline. No antagonism for cephalexin-gentamicin combination was observed for any bacterial strain.