Depletion of colistin in eggs following medication of laying hens.

The depletion of colistin in eggs was determined separately for the albumen, the yolk and the whole egg after oral and intramuscular administrations of colistin sulphate. Residues were assayed by an agar plate diffusion method with Bordetella bronchoseptica ATCC 4617 as test organism. Colistin residues were not detected after drug administration by the oral route, but could be detected in the yolk until eight days after intramuscular injection. The total amount excreted represented 0.9% of the dose applied.