Bacterial flora isolated from the lungs of calves with pneumonia and theirresistance patterns to antimicrobial drugs

The population under study included young calves with pneumonia (group A, n =13) and their controls (group B, n=9), as well as older calves from which the lungs with (group C, n=90) or without (group D, n=10) lesions were coll ected after slaughter. Arcanobacterium pyogenes was the organism most commonly isolated from calve s in group A (46%), followed by Haemophilus somnus (23%), Mannheimia haemol ytica (15%), Streptococcus suis and Pasteurella multocida (7.7% each). Only S. suis (22%) and P multocida (11%) were found in group B. P. multocida wa s isolated from 32% group C calves, H.somnus from 11%, A. pyogenes from 7.8 %, M. haemolytica from 2.2% and S. suis from 1.1%. No specific pathogens we re isolated in group D. Prevalence of Mycoplasma bovis infection was 69% in group A and 37% in group C. Ninety-eight strains were tested for resistence to antibiotics. Resistence to penicillin and ampicillin was present only in M, haemolytica (46%). High percentages of resistent strains were observed for streptomycin (48-100%), tetracycline (15-43%), sulfonamides alone (14-100%) or in combination with trimethoprim (0-100%). Therapeutic approaches to bacterial calf pneumonia in the area under study should be modified according to the isolated bacterial population, the obse rved antimicrobial resistances and the growing importance of Mycoplasma bov is.