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J Clin Microbiol. 2012 Jul;50(7):2224-8. doi: 10.1128/JCM.00675-12. Epub 2012 Apr 18.

Analysis of a Streptococcus pyogenes puerperal sepsis cluster by use of whole-genome sequencing.

Author information

1
School of Chemistry and Molecular Biosciences and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, Australia.

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.

PMID:
22518858
PMCID:
PMC3405596
DOI:
10.1128/JCM.00675-12
[Indexed for MEDLINE]
Free PMC Article

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