Resistance of gram-negative bacteria to antibiotics in large calf agglomerations.

The antibiotic resistance of E. coli, Citrobacter, Enterobacter-Klebsiella and Pseudomonas aeruginosa strains isolated from calves was tested. A high proportion of multiresistance was found even in E. coli strains isolated from newborn calves. Gram-negative bacteria isolated from animals in three large calfhouses were almost 100% resistant to ampicillin, tetracyclines and sulphonamides. Multiresistance was general and varied from 5 to 12 antibiotics among different strains. Initial high sensitivity to antibiotics which had never been used before was observed. Antibiotic resistance rapidly increased after use started. The usefulness of antibiotics in E. coli induced diarrhea is questioned and oral rehydration is appraised.