Colonization priority among Staphylococcus aureus strains--correlation with phage-type.

We have studied the distribution of phage-type patterns among strains of Staphylococcus aureus isolated from patients in a burns unit. From 51 patients the same phage-type was isolated from succeeding swabs during the observation period. In 20 patients new types were introduced, but the original strain remained. In 23 patients the first strain was replaced by one other strain, in eight patients two or more. Strains of type 95 seemed to have a high colonization priority, whereas strains of group III had a low one. In 1986 phage-typing was performed on two or more S. aureus strains from the same patient, in 4561 instances. Recurrence of strains of the same phage-type pattern was demonstrated in 70% of the patients when the first and the fourth sample were compared. The "newer epidemic" strains of phage-type 95 and of the 94,96 complex had the highest percentage of recurrence (more than 80%) when adjacent samples were compared, and 68-69% when the first and the fourth sample were compared. The good colonization capacity of these strains might be one of the explanations why they occur frequently today although they are resistant only to penicillin.