1566. Whole-Genome Sequencing of Methicillin-Resistant Staphylococcus aureus Isolated From Pediatric Acute Hematogenous Osteomyelitis: Single Nucleotide Polymorphisms Analysis Within a Single Community and Its Association With Clinical Severity of Illness
Session: Poster Abstract Session: Microbial and Host Genetic Factors in Disease
Saturday, October 5, 2013
Room: The Moscone Center: Poster Hall C
Posters
  • SNPsPOSTERIDSA 9-26-13 Final changes.pdf (770.9 kB)
  • Background: Pediatric osteomyelitis due to Methicillin-Resistant Staphylococcus aureus (MRSA) demonstrates a spectrum of clinical manifestations ranging from mild to severe.  USA 300 is currently the most common community acquired isolate.   Clinical variability may be due to genomic diversity of the causative organism which is not differentiated by multi-locus sequence typing (MLST). The aim of this study was to identify unique genetic features of MRSA isolates among children who have a diverse spectrum of illness within a single community using next generation sequencing (NGS) and optical mapping (OpGen).

    Methods: Children with MRSA osteomyelitis were prospectively studied between July 2010 and April 2011 to calculate a severity of illness score from objective parameters.  The bacterial isolates were studied with whole-genome sequencing on an Illumina Hiseq platform.  OpGen was used to find the closest related bacterial strain to be used as a reference for analyzing the sequence data.  NGS and OpGen methods were combined for the synergistic detection of insertion and deletion events, gene rearrangements, copy number variations and variant detection.  Sequence data was also used for MLST and multi-virulence locus sequence typing (MVLST). 

    Results: The twelve children studied demonstrated substantial variation in severity of illness scores. OpGen evaluation of the bacterial isolates showed closest similarity to USA300.    This was confirmed for all twelve samples by NGS.  MLST confirmed that all isolates were sequence type (ST) 8 and SCCmecIVa.  OpGen and NGS differentiated the isolates from USA300 by identifying the presence and location of insertions (40 kb) and deletions (range 8-17 kb) in various specimens.  No rearrangements were identified.   MVLST revealed differences between the isolates and USA300 in two virulence loci and differences among the isolates in the gamma hemolysin (HlgA) locus.   NGS demonstrated the bacterial genetic heterogeneity of these MRSA isolates with an average of 11 strain specific, non-synonymous single nucleotide polymorphisms. 

    Conclusion: Whole genome sequencing by NGS and OpGen differentiated our isolates from USA300 and from one another.  These variations may play a role in the pathogenesis of the varying clinical severity in these children.

    Claudia Gaviria, MD, Pediatric Infectious Diseases, UT Southwestern Dallas, Dallas, TX, Edward K. Wakeland, PhD, Immunology, University of Texas Southwestern Medical Center, Dallas, TX, Lawson Copley, MD, Orthopaedic Surgery, UT Southwestern Dallas, Dallas, TX and Chukwuemika Aroh, PhD, Immunology, UT Southwestern, Dallas, TX

    Disclosures:

    C. Gaviria, None

    E. K. Wakeland, None

    L. Copley, None

    C. Aroh, None

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