PCR of S. aureus strains showing ETA and ETB genes. Single-cell colonies of S. aureus strains were subjected to PCR analysis, and the products were analyzed on agerose gel electrophoresis, as described in the Materials and Methods section. Lane M contains kilobase standards. Lanes 2, 4, 5, and 10 are samples from ETA producers. Lanes 3 and 11 are samples from ETB producers. Lanes 6 and 7 are samples that are both ETA and ETB producers. Lanes 8 and 9 are samples from TSST-1 producers (negative controls).