Antimicrobial susceptibility of bifidobacteria isolated from gastrointestinal tract of calves

Fifty bifidobacterial strains isolated from different parts of gastrointestinal tract of calves during the milk-feeding period were tested for susceptibility to 28 antibiotics using disc diffusion method on TPY agar. Spectrum of antibiotics included commonly used medicaments in veterinary medicine. Seven strains from culture collection DSMZ were taken as a control. Most of the strains tested were susceptible to penicillins, cephalosporins, macrolids, chloramphenicols, bacitracin, linkomycin and resistant to aminoglycosides and aminocyclitols, quinolones, sulphonamides and colistin sulphate. All tetracyclines and enrofloxacin showed a variable effect against bifidobacterial strains. Our results suggest that strains resistant to antibiotics tested seem to be suitable for administration to young ruminants during antibiotic treatment. (c) 2006 Elsevier B.V. All rights reserved.