[Sensitivity of 30 strains of E. coli isolated from calves to chemotherapeutic agents].

Escherichia coli strains were isolated from calves and were biochemically and serologically identified in terms of their sensitivity to antibiotics. An exclusively high frequency of sensitivity was established to sulfonamides (100 per cent), tetracicline, erythromycin, oleandomycin (86.6 per cent) ampicillin, and streptomycin (70 per cent). Well expressed was their sensitivity to nitrofurans, canamycin, neomycin, and polymyxin. It was demonstrated through serial dilutions that there exists a high level of resistance to sulfanilamides, oleandomycin, erytromycin, tetracycline, streptomycin, chloramphenicol (more than 512 mug/cm3). The prevalence of such polyresistand E. coli strains in calves is the reason for concern in the district of Haskovo.