Minimum inhibitory concentrations (MIC) of frequently used chemotherapeutics present in agents pathogenic to animals as ascertained by multicentric systems in Germany - Part III: Pasteurella and mannheimia spp. (Pasteurella multocida, Mannheimia haemolytica)

As part of a study on the quantitative determination of resistance in veter inary pathogens (see part I), the micro broth dilution test was used to det ermine the minimal inhibitory concentration (MIC) for 10-12 active antibact erial substances in 61 Pasteurella multocida isolates and 32 Mannheimia (Pa st.) haemolytica isolates from cattle and in 79 Pasteurella multocida strai ns isolated from pigs. The agents isolated in 1999 were put at the disposal of the BgVV by the directors of the participating veterinary laboratories (see part I). ten institutes in 7 Lander sent 61 bovine isolates of Pasteur ella multocida - originating from 37 different municipalities or towns - to the BgVV for determination of the MIG. Furthermore, 32 bovine strains of M annheimia (Past.) haemolytica, isolated by 11 institutes in 7 Lander and or iginating from 24 different municipalities/towns, were tested for sensitivi ty. In addition, 14 institutes in 7 Lander sent 79 porcine isolates of Past eurella multocida-originating from 64 different German municipalities/towns - to the BgVV for determination of the MIC. Simultaneously, the diameter o f the inhibitory zone was determined with the aid of the agar diffusion tes t. The MIC and the inhibitory zone diameters were evaluated according to li mit values, most of which were adopted by the German standard DIN 58940 and included in a veterinary protocol for the determination of resistance in f ast-growing bacteria. 1.8 per ent of the 61 Pasteurella multocida strains o f bovine origin were found to be resistant to potentiated sulfonamides, 3.3 per cent to florfenicol, 8.5 per cent to cephalosporins (3(rd) generation) , 7.2 per cent to tetracyclins, 10.5 per cent to benzylpenicillin, 14.8 per cent to ampicillin, and 98.1 per cent to tylosin. No strain was found to b e resistant to enrofloxacin. 6.2 per cent of the 32 Mannheimia (Past) haemo lytica were found to be resistant to florfenicol, 9.3 per cent to potentiat ed sulfonamides, 15.6 per cent to ampicillin, 15.5 per cent to tetracycline s, and 16 per cent to benzylpenicillin, No strain was found to be resistant to enrofloxacin. 2.5 per cent of the 79 Pasteurella multocida strains of p orcine origin were found to be resistant to enrofloxacin, 7.4 per cent, to cephalosporins (3(rd) generation), 15.8 per cent, to benzylpenicillin, 15 p er cent, to ampicillin, 1.3 per cent, to florfenicol, 11.4 per cent, to tet ra- cyclines, 11.5 per cent, to potentiated sulfonamides and 100 per cent, to tylosin. In the conclusions, some aspects of a national resistance monit oring of zoonotic and animal pathogens in food producing animals are discus sed and attention is drawn to the importance of the frequency of resistance for specific antibiotic therapies.