A Practical Evaluation of the Delvotest P Multi Plate Test in Screening Raw Milk for Antibiotics.

The Delvotest P Multi plate test was evaluated by screening 100 milk samples for total antibiotic residues (penicillin G, streptomycin and neomycin). The samples were taken in conjunction with an antibiotic depletion study in milk derived from six cows treated with a multiple antibiotic, intramammary infusion product. Within the limits of sensitivity of the Delvotest, only penicillin G persisted in milk samples taken beyond 60 h, whereas in some samples, the other antibiotics appeared to be depleted as early as 48 h. More sensitive tests, however, detected neomycin ( Staphylococcus epidermidis , ATCC 12228) in 50% of samples taken at 60 h and streptomycin ( Bacillus subtilis , ATCC 6633) at 14.5 d after discontinuation of infusion.