In vitro antibacterial activity of enrofloxacin and ciprofloxacin in combination against Escherichia coli and staphylococcal clinical isolates from dogs

SUMMARY The objective of the study was to determine the in vitro interaction between enrofloxacin and ciprofloxacin against Escherichia coli and staphylococcal isolates from dogs. The microdilution checkerboard assay was used to determine the interaction of the drugs against 50 E coli and 50 β-haemolytic staphylococcal clinical isolates. The checkerboard assay revealed that the activity of enrofloxacin and ciprofloxacin was additive against E coli and staphylococcal clinical isolates. It was concluded that for bacterial species against which ciprofloxacin is more potent than enrofloxacin, the in vivo transformation of enrofloxacin to ciprofloxacin may enhance the efficacy of enrofloxacin, if additivity of the drugs is confirmed in vivo.