Analysis of a Streptococcus pyogenes puerperal sepsis cluster using whole-genome sequencing

Between June and November 2010, a concerning rise in the number of puerperal sepsis cases was observed in the New South Wales hospital system. Group A streptococci (GAS; Streptococcus pyogenes) isolates PS001-011 were recovered from nine patients. Pulse-field gel electrophoresis and emm sequence typing revealed GAS of emm1.40, emm75.0, emm77.0, emm89.0, and emm89.9 were each recovered from a single patient, ruling out a single source of infection. However, emm28.8 GAS were recovered from four different patients. To investigate the relatedness of these emm28 isolates, whole-genome sequencing was undertaken and the genome sequences compared to that of the emm28.4 reference strain MGAS6180.