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

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

Characteristics and regional variations of group D streptococcal endocarditis in France.

International audienceThe proportion of infective endocarditis (IE) caused by group D streptococci (GDS; formerly Streptococcus bovis) increased markedly in France, to account for 25% of all cases of IE by 1999. In an attempt to explain this phenomenon, a comparative analysis of GDS and oral streptococci (OS) causing IE was performed. This study was based on data collected from a large cross-sectional population-based survey that was conducted in 1999. In total, 559 cases of definite IE were recorded, of which 142 involved GDS and 79 involved OS. Patients with GDS IE were older (62.7 vs. 56.6 years, p 0.01) and had a history of valve disease less frequently than did patients with OS IE (33.8% vs. 67.1%, p <0.0001). At-risk procedures for IE were performed less frequently in patients with GDS than in patients with OS (14.8% vs. 24.1%, p 0.08), but co-morbidities were more frequent in the GDS group (59.9% vs. 32.9%, p 0.0001). Diabetes, colon diseases and cirrhosis were also more frequent in the GDS group (p 0.006, p <0.0001 and p 0.08, respectively). Rural residents accounted for 31.0% of the GDS group, but for only 15.2% of the OS group (p 0.001). Likewise, the proportion of GDS IE was higher in regions with mixed (urban and rural) populations (Franche-Comté 81.8%, Marne 68.7%, Lorraine 70.3% and Rhône-Alpes 65.3%) than in exclusively urban regions (Paris and Ile de France 58.0%). Further investigations are required to elucidate the link in France between the incidence of GDS IE, rural residency and nutritional factors

Genome Analysis of Streptococcus pyogenes Associated with Pharyngitis and Skin Infections

Streptococcus pyogenes is a very important human pathogen, commonly associated with skin or throat infections but can also cause life-threatening situations including sepsis, streptococcal toxic shock syndrome, and necrotizing fasciitis. Various studies involving typing and molecular characterization of S. pyogenes have been published to date; however next-generation sequencing (NGS) studies provide a comprehensive collection of an organism's genetic variation. In this study, the genomes of nine S. pyogenes isolates associated with pharyngitis and skin infection were sequenced and studied for the presence of virulence genes, resistance elements, prophages, genomic recombination, and other genomic features. Additionally, a comparative phylogenetic analysis of the isolates with global clones highlighted their possible evolutionary lineage and their site of infection. The genomes were found to also house a multitude of features including gene regulation systems, virulence factors and antimicrobial resistance mechanisms