The bacterial resistance to cefoperazone: An evaluation of a German multicenter study

In a multicenter study 701 bacterial infectious agents of mastitis were iso lated from milk of dairy cows in II German institutes. The minimal inhibito ry concentration (MIC) and the inhibition zone diameter (IZD) of these isol ates to Cefoperazone were tested using the agar dilution test and the agar diffusion test: For Staphylococci the MIC50 values ranged between 0.5 mg/l and 2 mg/l, and for S. dysgalactiae, S. agalactiae and S. uberis the range was between 0.12 mg/l and 0.25 mg/l, E. coli and coliforms between 0.12 mg/ l and 0.25 mg/l. A. pyogenes had a MIC50 value of 0.03 mg/l. For the Entero cocci the MIC50 value was 4 mg/l, for P. aeruginosa the MIC50 valu was 8 mg /l. With the exception of the Enterococci the MIC90 values ranked above the MIC50 values by one concentration level. A new classification was made usi ng the fault minimizing method and the following evaluation cr-iter-ia were found: IZD: sensitive greater than or equal to 17 mm, intel mediate 11-16 mm, resi stant less than or equal to 10 mm MIG: sensitive less than or equal to 4 mg/l, intermediate 8-16 mg/l, resist ant greater than or equal to 32 mg/l These evaluation criteria were added to the tables for valuation of the IZD and the breakpoint concentrations of the antibiotics approved in veterinar y medicine by the Bundesinstitut fur gesundheitlichen Verbraucherschutz und Veterinarmedizin (BgVV tissue XII/99).