In vitro activity of flumequine in comparison with several other antimicrobial agents against five pathogens isolated in calves in the Netherlands

Summary The in vitro activity of flumequine in comparison with several other drugs was tested against 17 P. multocida, 16 P. haemolytica, 21 S. dublin, 21 S. typhimurium and 21 E. coli strains, isolated in (veal) calves in the Netherlands. The MIC50 of flumequine for the respective pasteurellas was 0.25 and 1 μg/ml, for the salmonellas and E. coli 0.5 μg/ml. In comparison with flumequine, enrofloxacin and ciprofloxacin showed higher in vitro activity, with MIC50 ≤ 0.008 μg/ml for ciprofloxacin. Decreased susceptibility of the pasteurellas was found for kanamycin, neomycin, streptomycin, gentamicin, oxytetracycline and doxycycline. The MIC50 of minocycline for P. multocida was 0.5 μg/ml and there was no cross resistance with the other tetracyclines. P. multocida was very susceptible to ampicillin (MIC50 ≤ 0.03 Ag/ml), P. haemolytica, however, was 100% resistant to this drug. Both pasteurellas were susceptible to cephalothin and approximately 50% of the strains of both bacteria were resistant to chloramphen...