FIG. 1.

PFGE of SmaI-digested chromosomal DNA from some S. uberis isolates from each herd over two successive lactations. The cow from which each sample was obtained is indicated. S1, S2, and S3, different sampling times as shown in Table 1, with S3 obtained in the subsequent lactation; LF, RF, LH, and RH, isolates obtained from the left fore-, right fore-, left hind-, and right hindquarters, respectively. The strain designation of each isolate is indicated at the bottom. Each panel shows isolates obtained from a single herd.