Introduction
Definition of Terms: A glossary of terms used in the present publication is included in a previous paper.1In the previous papers of this series, the results of two controlled investigations were reported, one carried out in a hospital nursery in Cincinnati2 and the other in Atlanta.3 Both studies demonstrated that the phenomenon of bacterial interference could be employed on a practical scale to prevent newborn colonization with hospital strains of staphylococci.However, because of low disease rates encountered among control infants in the Cincinnati study and the occurrence of a high incidence of spontaneous cross-infection with Staphylococcus aureus strain 502A in the Atlanta nursery, additional observations seemed desirable. Neither one of these factors affected the validity or the interpretation of the data; nevertheless, it was felt that another series of observations under different conditions would be of value.During March, April, and May of 1962,