title: Analysis of a Streptococcus pyogenes puerperal sepsis cluster by use of whole-genome sequencing.
abstract: Between June and November 2010, a concerning rise in the number of cases of puerperal sepsis, a postpartum pelvic bacterial infection contracted by women after childbirth, was observed in the New South Wales, Australia, hospital system. Group A streptococcus (GAS; Streptococcus pyogenes) isolates PS001 to PS011 were recovered from nine patients. Pulsed-field gel electrophoresis and emm sequence typing revealed that 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 were compared to the genome sequence of the emm28.4 reference strain, MGAS6180. A total of 186 single nucleotide polymorphisms were identified, for which the phylogenetic reconstruction indicated an outbreak of a polyclonal nature. While two isolates collected from different hospitals were not closely related, isolates from two puerperal sepsis patients from the same hospital were indistinguishable, suggesting patient-to-patient transmission or infection from a common source. The results of this study indicate that traditional typing protocols, such as pulsed-field gel electrophoresis, may not be sensitive enough to allow fine epidemiological discrimination of closely related bacterial isolates. Whole-genome sequencing presents a valid alternative that allows accurate fine-scale epidemiological investigation of bacterial infectious disease.
authors.affiliation: School of Chemistry and Molecular Biosciences and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia.
authors.forename: Nouri L
authors.initials: NL
authors.lastname: Ben Zakour
authors.forename: Carola
authors.initials: C
authors.lastname: Venturini
authors.forename: Scott A
authors.initials: SA
authors.lastname: Beatson
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Walker
mesh_terms: D000942:Antigens, Bacterial / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D016680:Genome, Bacterial; D015894:Genome, Human; D006801:Humans; D017720:Molecular Epidemiology; D058889:Molecular Typing; D009517:New South Wales / Q000453:epidemiology; D010802:Phylogeny; D011110:Polymorphism, Genetic; D011645:Puerperal Infection / Q000453:epidemiology / Q000382:microbiology*; D018805:Sepsis / Q000453:epidemiology / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013290:Streptococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; C014689:streptococcal M protein