A review of the medical considerations of the use of tylosin and other macrolide antibiotics as additives in animal feeds.

The use of antibiotics in animal feeds is reviewed with special reference to possible problems which might be encountered in human medicine. Emphasis is placed on the macrolide antibiotics, especially tylosin. Even though there can be cross-resistance between tylosin and erythromycin, the increasing use of tylosin in animal feeds has not caused an increase of resistance to erythromycin in human isolates of Staphylococcus aureus. There is no significant evidence that tylosin resistant staphylococci of animal origin have endangered human health. Tylosin is not effective against the gram-negative intestinal flora, which thus does not lead to selection of R-factors by conjugation. From the human medical stand point, there is no reason that precludes the use of tylosin as a fee additive in animal feeds.