Pattee, P. A. (Iowa State University, Ames) and J. N. Baldwin. Transduction of resistance to some macrolide antibiotics in Staphylococcus aureus. J. Bacteriol. 84:1049-1055. 1962.-By use of phage 80 of the International Typing Series, propagated on appropriate strains of Staphylococcus aureus, two related markers controlling resistance to certain macrolide antibiotics (erythromycin, oleandomycin, spiramycin, and carbomycin) were transduced among a variety of strains of S. aureus. Unlike the markers controlling penicillinase production and resistance to chlortetracycline and novobiocin, the determinants of resistance to the macrolide antibiotics were transduced at normal frequencies (at least 300 transductants per 10(9) phage) only to certain of the recipient strains. One of the markers studied appears to control an inducible enzyme system which is specifically induced by sub-inhibitory concentrations of erythromycin and which controls resistance to erythromycin, oleandomycin, spiramycin, and carbomycin. The other marker examined confers resistance to erythromycin, oleandomycin, spiramycin, and carbomycin, and shows no evidence of being dependent upon an inducible mechanism.