Lysogeny in pneumococci freshly isolated from man.

Twelve strains of encapsulated pneumococci isolated from patients with pneumococcal disease were examined for the presence of bacteriophage. Four of the strains yielded phage lytic for a noncapsulated indicator strain of pneumococcus. Three of the newly isolated bacteriophages differ serologically from pneumococcus bacteriophages described previously. The ability to yield lytic phage was lost by two of the lysogenic pneumococcal strains on repeated subculture.