Heterogeneity of hemolysin expression during neonatal Streptococcus agalactiae sepsis.

The beta-hemolysin of Streptococcus agalactiae is a major virulence factor; consequently, nonhemolytic strains rarely cause infections. We report on a case of neonatal sepsis caused by a strain displaying heterogeneous hemolysin expression. It was detected by the simultaneous isolation of hemolytic and nonhemolytic colonies from cultures of the infant's blood.