Bacteriophages of Streptococcus equi.

Bacteriophages were isolated from twelve lysogenic strains of Streptococcus equi. Based on sensitivity data and antiserum neutralization tests, the phage isolates were divided into two distinct but related groups. All twelve phage change the colonial morphology of S. equi from mucoid to matt. Possible phage-mediated effects on S. equi virulence are discussed.