Identification of a high-virulence clone of serotype III Streptococcus agalactiae by growth characterisitics at 40°C

A high-virulence clone of serotype III Streptococcus agalactiae causing invasive neonatal disease was previously identified by multilocus enzyme electrophoresis. A simple procedure involving growth at 40°C distinguished all isolates classified in this high-virulence clone from other serotype III isolates, which are more frequently associated with asymptomaticallly colonized infants, as well as the other serotypes of Group B streptococci. The high-virulence clone failed to grow at 40°C in FMC, a chemically defined medium, in contrast to the other organisms, which grew readily.